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Writing a Literature Review

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A literature review is a document or section of a document that collects key sources on a topic and discusses those sources in conversation with each other (also called synthesis ). The lit review is an important genre in many disciplines, not just literature (i.e., the study of works of literature such as novels and plays). When we say “literature review” or refer to “the literature,” we are talking about the research ( scholarship ) in a given field. You will often see the terms “the research,” “the scholarship,” and “the literature” used mostly interchangeably.

Where, when, and why would I write a lit review?

There are a number of different situations where you might write a literature review, each with slightly different expectations; different disciplines, too, have field-specific expectations for what a literature review is and does. For instance, in the humanities, authors might include more overt argumentation and interpretation of source material in their literature reviews, whereas in the sciences, authors are more likely to report study designs and results in their literature reviews; these differences reflect these disciplines’ purposes and conventions in scholarship. You should always look at examples from your own discipline and talk to professors or mentors in your field to be sure you understand your discipline’s conventions, for literature reviews as well as for any other genre.

A literature review can be a part of a research paper or scholarly article, usually falling after the introduction and before the research methods sections. In these cases, the lit review just needs to cover scholarship that is important to the issue you are writing about; sometimes it will also cover key sources that informed your research methodology.

Lit reviews can also be standalone pieces, either as assignments in a class or as publications. In a class, a lit review may be assigned to help students familiarize themselves with a topic and with scholarship in their field, get an idea of the other researchers working on the topic they’re interested in, find gaps in existing research in order to propose new projects, and/or develop a theoretical framework and methodology for later research. As a publication, a lit review usually is meant to help make other scholars’ lives easier by collecting and summarizing, synthesizing, and analyzing existing research on a topic. This can be especially helpful for students or scholars getting into a new research area, or for directing an entire community of scholars toward questions that have not yet been answered.

What are the parts of a lit review?

Most lit reviews use a basic introduction-body-conclusion structure; if your lit review is part of a larger paper, the introduction and conclusion pieces may be just a few sentences while you focus most of your attention on the body. If your lit review is a standalone piece, the introduction and conclusion take up more space and give you a place to discuss your goals, research methods, and conclusions separately from where you discuss the literature itself.

Introduction:

  • An introductory paragraph that explains what your working topic and thesis is
  • A forecast of key topics or texts that will appear in the review
  • Potentially, a description of how you found sources and how you analyzed them for inclusion and discussion in the review (more often found in published, standalone literature reviews than in lit review sections in an article or research paper)
  • Summarize and synthesize: Give an overview of the main points of each source and combine them into a coherent whole
  • Analyze and interpret: Don’t just paraphrase other researchers – add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
  • Critically Evaluate: Mention the strengths and weaknesses of your sources
  • Write in well-structured paragraphs: Use transition words and topic sentence to draw connections, comparisons, and contrasts.

Conclusion:

  • Summarize the key findings you have taken from the literature and emphasize their significance
  • Connect it back to your primary research question

How should I organize my lit review?

Lit reviews can take many different organizational patterns depending on what you are trying to accomplish with the review. Here are some examples:

  • Chronological : The simplest approach is to trace the development of the topic over time, which helps familiarize the audience with the topic (for instance if you are introducing something that is not commonly known in your field). If you choose this strategy, be careful to avoid simply listing and summarizing sources in order. Try to analyze the patterns, turning points, and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred (as mentioned previously, this may not be appropriate in your discipline — check with a teacher or mentor if you’re unsure).
  • Thematic : If you have found some recurring central themes that you will continue working with throughout your piece, you can organize your literature review into subsections that address different aspects of the topic. For example, if you are reviewing literature about women and religion, key themes can include the role of women in churches and the religious attitude towards women.
  • Qualitative versus quantitative research
  • Empirical versus theoretical scholarship
  • Divide the research by sociological, historical, or cultural sources
  • Theoretical : In many humanities articles, the literature review is the foundation for the theoretical framework. You can use it to discuss various theories, models, and definitions of key concepts. You can argue for the relevance of a specific theoretical approach or combine various theorical concepts to create a framework for your research.

What are some strategies or tips I can use while writing my lit review?

Any lit review is only as good as the research it discusses; make sure your sources are well-chosen and your research is thorough. Don’t be afraid to do more research if you discover a new thread as you’re writing. More info on the research process is available in our "Conducting Research" resources .

As you’re doing your research, create an annotated bibliography ( see our page on the this type of document ). Much of the information used in an annotated bibliography can be used also in a literature review, so you’ll be not only partially drafting your lit review as you research, but also developing your sense of the larger conversation going on among scholars, professionals, and any other stakeholders in your topic.

Usually you will need to synthesize research rather than just summarizing it. This means drawing connections between sources to create a picture of the scholarly conversation on a topic over time. Many student writers struggle to synthesize because they feel they don’t have anything to add to the scholars they are citing; here are some strategies to help you:

  • It often helps to remember that the point of these kinds of syntheses is to show your readers how you understand your research, to help them read the rest of your paper.
  • Writing teachers often say synthesis is like hosting a dinner party: imagine all your sources are together in a room, discussing your topic. What are they saying to each other?
  • Look at the in-text citations in each paragraph. Are you citing just one source for each paragraph? This usually indicates summary only. When you have multiple sources cited in a paragraph, you are more likely to be synthesizing them (not always, but often
  • Read more about synthesis here.

The most interesting literature reviews are often written as arguments (again, as mentioned at the beginning of the page, this is discipline-specific and doesn’t work for all situations). Often, the literature review is where you can establish your research as filling a particular gap or as relevant in a particular way. You have some chance to do this in your introduction in an article, but the literature review section gives a more extended opportunity to establish the conversation in the way you would like your readers to see it. You can choose the intellectual lineage you would like to be part of and whose definitions matter most to your thinking (mostly humanities-specific, but this goes for sciences as well). In addressing these points, you argue for your place in the conversation, which tends to make the lit review more compelling than a simple reporting of other sources.

do literature reviews have results

What is a Literature Review? How to Write It (with Examples)

literature review

A literature review is a critical analysis and synthesis of existing research on a particular topic. It provides an overview of the current state of knowledge, identifies gaps, and highlights key findings in the literature. 1 The purpose of a literature review is to situate your own research within the context of existing scholarship, demonstrating your understanding of the topic and showing how your work contributes to the ongoing conversation in the field. Learning how to write a literature review is a critical tool for successful research. Your ability to summarize and synthesize prior research pertaining to a certain topic demonstrates your grasp on the topic of study, and assists in the learning process. 

Table of Contents

What is the purpose of literature review , a. habitat loss and species extinction: , b. range shifts and phenological changes: , c. ocean acidification and coral reefs: , d. adaptive strategies and conservation efforts: .

  • Choose a Topic and Define the Research Question: 
  • Decide on the Scope of Your Review: 
  • Select Databases for Searches: 
  • Conduct Searches and Keep Track: 
  • Review the Literature: 
  • Organize and Write Your Literature Review: 
  • How to write a literature review faster with Paperpal? 

Frequently asked questions 

What is a literature review .

A well-conducted literature review demonstrates the researcher’s familiarity with the existing literature, establishes the context for their own research, and contributes to scholarly conversations on the topic. One of the purposes of a literature review is also to help researchers avoid duplicating previous work and ensure that their research is informed by and builds upon the existing body of knowledge.

do literature reviews have results

A literature review serves several important purposes within academic and research contexts. Here are some key objectives and functions of a literature review: 2  

1. Contextualizing the Research Problem: The literature review provides a background and context for the research problem under investigation. It helps to situate the study within the existing body of knowledge. 

2. Identifying Gaps in Knowledge: By identifying gaps, contradictions, or areas requiring further research, the researcher can shape the research question and justify the significance of the study. This is crucial for ensuring that the new research contributes something novel to the field.

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3. Understanding Theoretical and Conceptual Frameworks: Literature reviews help researchers gain an understanding of the theoretical and conceptual frameworks used in previous studies. This aids in the development of a theoretical framework for the current research. 

4. Providing Methodological Insights: Another purpose of literature reviews is that it allows researchers to learn about the methodologies employed in previous studies. This can help in choosing appropriate research methods for the current study and avoiding pitfalls that others may have encountered. 

5. Establishing Credibility: A well-conducted literature review demonstrates the researcher’s familiarity with existing scholarship, establishing their credibility and expertise in the field. It also helps in building a solid foundation for the new research. 

6. Informing Hypotheses or Research Questions: The literature review guides the formulation of hypotheses or research questions by highlighting relevant findings and areas of uncertainty in existing literature. 

Literature review example 

Let’s delve deeper with a literature review example: Let’s say your literature review is about the impact of climate change on biodiversity. You might format your literature review into sections such as the effects of climate change on habitat loss and species extinction, phenological changes, and marine biodiversity. Each section would then summarize and analyze relevant studies in those areas, highlighting key findings and identifying gaps in the research. The review would conclude by emphasizing the need for further research on specific aspects of the relationship between climate change and biodiversity. The following literature review template provides a glimpse into the recommended literature review structure and content, demonstrating how research findings are organized around specific themes within a broader topic. 

Literature Review on Climate Change Impacts on Biodiversity:  

Climate change is a global phenomenon with far-reaching consequences, including significant impacts on biodiversity. This literature review synthesizes key findings from various studies: 

Climate change-induced alterations in temperature and precipitation patterns contribute to habitat loss, affecting numerous species (Thomas et al., 2004). The review discusses how these changes increase the risk of extinction, particularly for species with specific habitat requirements. 

Observations of range shifts and changes in the timing of biological events (phenology) are documented in response to changing climatic conditions (Parmesan & Yohe, 2003). These shifts affect ecosystems and may lead to mismatches between species and their resources. 

The review explores the impact of climate change on marine biodiversity, emphasizing ocean acidification’s threat to coral reefs (Hoegh-Guldberg et al., 2007). Changes in pH levels negatively affect coral calcification, disrupting the delicate balance of marine ecosystems. 

Recognizing the urgency of the situation, the literature review discusses various adaptive strategies adopted by species and conservation efforts aimed at mitigating the impacts of climate change on biodiversity (Hannah et al., 2007). It emphasizes the importance of interdisciplinary approaches for effective conservation planning. 

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How to write a good literature review 

Writing a literature review involves summarizing and synthesizing existing research on a particular topic. A good literature review format should include the following elements. 

Introduction: The introduction sets the stage for your literature review, providing context and introducing the main focus of your review. 

  • Opening Statement: Begin with a general statement about the broader topic and its significance in the field. 
  • Scope and Purpose: Clearly define the scope of your literature review. Explain the specific research question or objective you aim to address. 
  • Organizational Framework: Briefly outline the structure of your literature review, indicating how you will categorize and discuss the existing research. 
  • Significance of the Study: Highlight why your literature review is important and how it contributes to the understanding of the chosen topic. 
  • Thesis Statement: Conclude the introduction with a concise thesis statement that outlines the main argument or perspective you will develop in the body of the literature review. 

Body: The body of the literature review is where you provide a comprehensive analysis of existing literature, grouping studies based on themes, methodologies, or other relevant criteria. 

  • Organize by Theme or Concept: Group studies that share common themes, concepts, or methodologies. Discuss each theme or concept in detail, summarizing key findings and identifying gaps or areas of disagreement. 
  • Critical Analysis: Evaluate the strengths and weaknesses of each study. Discuss the methodologies used, the quality of evidence, and the overall contribution of each work to the understanding of the topic. 
  • Synthesis of Findings: Synthesize the information from different studies to highlight trends, patterns, or areas of consensus in the literature. 
  • Identification of Gaps: Discuss any gaps or limitations in the existing research and explain how your review contributes to filling these gaps. 
  • Transition between Sections: Provide smooth transitions between different themes or concepts to maintain the flow of your literature review. 
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Conclusion: The conclusion of your literature review should summarize the main findings, highlight the contributions of the review, and suggest avenues for future research. 

  • Summary of Key Findings: Recap the main findings from the literature and restate how they contribute to your research question or objective. 
  • Contributions to the Field: Discuss the overall contribution of your literature review to the existing knowledge in the field. 
  • Implications and Applications: Explore the practical implications of the findings and suggest how they might impact future research or practice. 
  • Recommendations for Future Research: Identify areas that require further investigation and propose potential directions for future research in the field. 
  • Final Thoughts: Conclude with a final reflection on the importance of your literature review and its relevance to the broader academic community. 

what is a literature review

Conducting a literature review 

Conducting a literature review is an essential step in research that involves reviewing and analyzing existing literature on a specific topic. It’s important to know how to do a literature review effectively, so here are the steps to follow: 1  

Choose a Topic and Define the Research Question:  

  • Select a topic that is relevant to your field of study. 
  • Clearly define your research question or objective. Determine what specific aspect of the topic do you want to explore? 

Decide on the Scope of Your Review:  

  • Determine the timeframe for your literature review. Are you focusing on recent developments, or do you want a historical overview? 
  • Consider the geographical scope. Is your review global, or are you focusing on a specific region? 
  • Define the inclusion and exclusion criteria. What types of sources will you include? Are there specific types of studies or publications you will exclude? 

Select Databases for Searches:  

  • Identify relevant databases for your field. Examples include PubMed, IEEE Xplore, Scopus, Web of Science, and Google Scholar. 
  • Consider searching in library catalogs, institutional repositories, and specialized databases related to your topic. 

Conduct Searches and Keep Track:  

  • Develop a systematic search strategy using keywords, Boolean operators (AND, OR, NOT), and other search techniques. 
  • Record and document your search strategy for transparency and replicability. 
  • Keep track of the articles, including publication details, abstracts, and links. Use citation management tools like EndNote, Zotero, or Mendeley to organize your references. 

Review the Literature:  

  • Evaluate the relevance and quality of each source. Consider the methodology, sample size, and results of studies. 
  • Organize the literature by themes or key concepts. Identify patterns, trends, and gaps in the existing research. 
  • Summarize key findings and arguments from each source. Compare and contrast different perspectives. 
  • Identify areas where there is a consensus in the literature and where there are conflicting opinions. 
  • Provide critical analysis and synthesis of the literature. What are the strengths and weaknesses of existing research? 

Organize and Write Your Literature Review:  

  • Literature review outline should be based on themes, chronological order, or methodological approaches. 
  • Write a clear and coherent narrative that synthesizes the information gathered. 
  • Use proper citations for each source and ensure consistency in your citation style (APA, MLA, Chicago, etc.). 
  • Conclude your literature review by summarizing key findings, identifying gaps, and suggesting areas for future research. 

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do literature reviews have results

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A literature review is a critical and comprehensive analysis of existing literature (published and unpublished works) on a specific topic or research question and provides a synthesis of the current state of knowledge in a particular field. A well-conducted literature review is crucial for researchers to build upon existing knowledge, avoid duplication of efforts, and contribute to the advancement of their field. It also helps researchers situate their work within a broader context and facilitates the development of a sound theoretical and conceptual framework for their studies.

Literature review is a crucial component of research writing, providing a solid background for a research paper’s investigation. The aim is to keep professionals up to date by providing an understanding of ongoing developments within a specific field, including research methods, and experimental techniques used in that field, and present that knowledge in the form of a written report. Also, the depth and breadth of the literature review emphasizes the credibility of the scholar in his or her field.  

Before writing a literature review, it’s essential to undertake several preparatory steps to ensure that your review is well-researched, organized, and focused. This includes choosing a topic of general interest to you and doing exploratory research on that topic, writing an annotated bibliography, and noting major points, especially those that relate to the position you have taken on the topic. 

Literature reviews and academic research papers are essential components of scholarly work but serve different purposes within the academic realm. 3 A literature review aims to provide a foundation for understanding the current state of research on a particular topic, identify gaps or controversies, and lay the groundwork for future research. Therefore, it draws heavily from existing academic sources, including books, journal articles, and other scholarly publications. In contrast, an academic research paper aims to present new knowledge, contribute to the academic discourse, and advance the understanding of a specific research question. Therefore, it involves a mix of existing literature (in the introduction and literature review sections) and original data or findings obtained through research methods. 

Literature reviews are essential components of academic and research papers, and various strategies can be employed to conduct them effectively. If you want to know how to write a literature review for a research paper, here are four common approaches that are often used by researchers.  Chronological Review: This strategy involves organizing the literature based on the chronological order of publication. It helps to trace the development of a topic over time, showing how ideas, theories, and research have evolved.  Thematic Review: Thematic reviews focus on identifying and analyzing themes or topics that cut across different studies. Instead of organizing the literature chronologically, it is grouped by key themes or concepts, allowing for a comprehensive exploration of various aspects of the topic.  Methodological Review: This strategy involves organizing the literature based on the research methods employed in different studies. It helps to highlight the strengths and weaknesses of various methodologies and allows the reader to evaluate the reliability and validity of the research findings.  Theoretical Review: A theoretical review examines the literature based on the theoretical frameworks used in different studies. This approach helps to identify the key theories that have been applied to the topic and assess their contributions to the understanding of the subject.  It’s important to note that these strategies are not mutually exclusive, and a literature review may combine elements of more than one approach. The choice of strategy depends on the research question, the nature of the literature available, and the goals of the review. Additionally, other strategies, such as integrative reviews or systematic reviews, may be employed depending on the specific requirements of the research.

The literature review format can vary depending on the specific publication guidelines. However, there are some common elements and structures that are often followed. Here is a general guideline for the format of a literature review:  Introduction:   Provide an overview of the topic.  Define the scope and purpose of the literature review.  State the research question or objective.  Body:   Organize the literature by themes, concepts, or chronology.  Critically analyze and evaluate each source.  Discuss the strengths and weaknesses of the studies.  Highlight any methodological limitations or biases.  Identify patterns, connections, or contradictions in the existing research.  Conclusion:   Summarize the key points discussed in the literature review.  Highlight the research gap.  Address the research question or objective stated in the introduction.  Highlight the contributions of the review and suggest directions for future research.

Both annotated bibliographies and literature reviews involve the examination of scholarly sources. While annotated bibliographies focus on individual sources with brief annotations, literature reviews provide a more in-depth, integrated, and comprehensive analysis of existing literature on a specific topic. The key differences are as follows: 

  Annotated Bibliography  Literature Review 
Purpose  List of citations of books, articles, and other sources with a brief description (annotation) of each source.  Comprehensive and critical analysis of existing literature on a specific topic. 
Focus  Summary and evaluation of each source, including its relevance, methodology, and key findings.  Provides an overview of the current state of knowledge on a particular subject and identifies gaps, trends, and patterns in existing literature. 
Structure  Each citation is followed by a concise paragraph (annotation) that describes the source’s content, methodology, and its contribution to the topic.  The literature review is organized thematically or chronologically and involves a synthesis of the findings from different sources to build a narrative or argument. 
Length  Typically 100-200 words  Length of literature review ranges from a few pages to several chapters 
Independence  Each source is treated separately, with less emphasis on synthesizing the information across sources.  The writer synthesizes information from multiple sources to present a cohesive overview of the topic. 

References 

  • Denney, A. S., & Tewksbury, R. (2013). How to write a literature review.  Journal of criminal justice education ,  24 (2), 218-234. 
  • Pan, M. L. (2016).  Preparing literature reviews: Qualitative and quantitative approaches . Taylor & Francis. 
  • Cantero, C. (2019). How to write a literature review.  San José State University Writing Center . 

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  • How to Write a Literature Review | Guide, Examples, & Templates

How to Write a Literature Review | Guide, Examples, & Templates

Published on January 2, 2023 by Shona McCombes . Revised on September 11, 2023.

What is a literature review? A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research that you can later apply to your paper, thesis, or dissertation topic .

There are five key steps to writing a literature review:

  • Search for relevant literature
  • Evaluate sources
  • Identify themes, debates, and gaps
  • Outline the structure
  • Write your literature review

A good literature review doesn’t just summarize sources—it analyzes, synthesizes , and critically evaluates to give a clear picture of the state of knowledge on the subject.

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Table of contents

What is the purpose of a literature review, examples of literature reviews, step 1 – search for relevant literature, step 2 – evaluate and select sources, step 3 – identify themes, debates, and gaps, step 4 – outline your literature review’s structure, step 5 – write your literature review, free lecture slides, other interesting articles, frequently asked questions, introduction.

  • Quick Run-through
  • Step 1 & 2

When you write a thesis , dissertation , or research paper , you will likely have to conduct a literature review to situate your research within existing knowledge. The literature review gives you a chance to:

  • Demonstrate your familiarity with the topic and its scholarly context
  • Develop a theoretical framework and methodology for your research
  • Position your work in relation to other researchers and theorists
  • Show how your research addresses a gap or contributes to a debate
  • Evaluate the current state of research and demonstrate your knowledge of the scholarly debates around your topic.

Writing literature reviews is a particularly important skill if you want to apply for graduate school or pursue a career in research. We’ve written a step-by-step guide that you can follow below.

Literature review guide

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See an example

do literature reviews have results

Writing literature reviews can be quite challenging! A good starting point could be to look at some examples, depending on what kind of literature review you’d like to write.

  • Example literature review #1: “Why Do People Migrate? A Review of the Theoretical Literature” ( Theoretical literature review about the development of economic migration theory from the 1950s to today.)
  • Example literature review #2: “Literature review as a research methodology: An overview and guidelines” ( Methodological literature review about interdisciplinary knowledge acquisition and production.)
  • Example literature review #3: “The Use of Technology in English Language Learning: A Literature Review” ( Thematic literature review about the effects of technology on language acquisition.)
  • Example literature review #4: “Learners’ Listening Comprehension Difficulties in English Language Learning: A Literature Review” ( Chronological literature review about how the concept of listening skills has changed over time.)

You can also check out our templates with literature review examples and sample outlines at the links below.

Download Word doc Download Google doc

Before you begin searching for literature, you need a clearly defined topic .

If you are writing the literature review section of a dissertation or research paper, you will search for literature related to your research problem and questions .

Make a list of keywords

Start by creating a list of keywords related to your research question. Include each of the key concepts or variables you’re interested in, and list any synonyms and related terms. You can add to this list as you discover new keywords in the process of your literature search.

  • Social media, Facebook, Instagram, Twitter, Snapchat, TikTok
  • Body image, self-perception, self-esteem, mental health
  • Generation Z, teenagers, adolescents, youth

Search for relevant sources

Use your keywords to begin searching for sources. Some useful databases to search for journals and articles include:

  • Your university’s library catalogue
  • Google Scholar
  • Project Muse (humanities and social sciences)
  • Medline (life sciences and biomedicine)
  • EconLit (economics)
  • Inspec (physics, engineering and computer science)

You can also use boolean operators to help narrow down your search.

Make sure to read the abstract to find out whether an article is relevant to your question. When you find a useful book or article, you can check the bibliography to find other relevant sources.

You likely won’t be able to read absolutely everything that has been written on your topic, so it will be necessary to evaluate which sources are most relevant to your research question.

For each publication, ask yourself:

  • What question or problem is the author addressing?
  • What are the key concepts and how are they defined?
  • What are the key theories, models, and methods?
  • Does the research use established frameworks or take an innovative approach?
  • What are the results and conclusions of the study?
  • How does the publication relate to other literature in the field? Does it confirm, add to, or challenge established knowledge?
  • What are the strengths and weaknesses of the research?

Make sure the sources you use are credible , and make sure you read any landmark studies and major theories in your field of research.

You can use our template to summarize and evaluate sources you’re thinking about using. Click on either button below to download.

Take notes and cite your sources

As you read, you should also begin the writing process. Take notes that you can later incorporate into the text of your literature review.

It is important to keep track of your sources with citations to avoid plagiarism . It can be helpful to make an annotated bibliography , where you compile full citation information and write a paragraph of summary and analysis for each source. This helps you remember what you read and saves time later in the process.

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do literature reviews have results

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To begin organizing your literature review’s argument and structure, be sure you understand the connections and relationships between the sources you’ve read. Based on your reading and notes, you can look for:

  • Trends and patterns (in theory, method or results): do certain approaches become more or less popular over time?
  • Themes: what questions or concepts recur across the literature?
  • Debates, conflicts and contradictions: where do sources disagree?
  • Pivotal publications: are there any influential theories or studies that changed the direction of the field?
  • Gaps: what is missing from the literature? Are there weaknesses that need to be addressed?

This step will help you work out the structure of your literature review and (if applicable) show how your own research will contribute to existing knowledge.

  • Most research has focused on young women.
  • There is an increasing interest in the visual aspects of social media.
  • But there is still a lack of robust research on highly visual platforms like Instagram and Snapchat—this is a gap that you could address in your own research.

There are various approaches to organizing the body of a literature review. Depending on the length of your literature review, you can combine several of these strategies (for example, your overall structure might be thematic, but each theme is discussed chronologically).

Chronological

The simplest approach is to trace the development of the topic over time. However, if you choose this strategy, be careful to avoid simply listing and summarizing sources in order.

Try to analyze patterns, turning points and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred.

If you have found some recurring central themes, you can organize your literature review into subsections that address different aspects of the topic.

For example, if you are reviewing literature about inequalities in migrant health outcomes, key themes might include healthcare policy, language barriers, cultural attitudes, legal status, and economic access.

Methodological

If you draw your sources from different disciplines or fields that use a variety of research methods , you might want to compare the results and conclusions that emerge from different approaches. For example:

  • Look at what results have emerged in qualitative versus quantitative research
  • Discuss how the topic has been approached by empirical versus theoretical scholarship
  • Divide the literature into sociological, historical, and cultural sources

Theoretical

A literature review is often the foundation for a theoretical framework . You can use it to discuss various theories, models, and definitions of key concepts.

You might argue for the relevance of a specific theoretical approach, or combine various theoretical concepts to create a framework for your research.

Like any other academic text , your literature review should have an introduction , a main body, and a conclusion . What you include in each depends on the objective of your literature review.

The introduction should clearly establish the focus and purpose of the literature review.

Depending on the length of your literature review, you might want to divide the body into subsections. You can use a subheading for each theme, time period, or methodological approach.

As you write, you can follow these tips:

  • Summarize and synthesize: give an overview of the main points of each source and combine them into a coherent whole
  • Analyze and interpret: don’t just paraphrase other researchers — add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
  • Critically evaluate: mention the strengths and weaknesses of your sources
  • Write in well-structured paragraphs: use transition words and topic sentences to draw connections, comparisons and contrasts

In the conclusion, you should summarize the key findings you have taken from the literature and emphasize their significance.

When you’ve finished writing and revising your literature review, don’t forget to proofread thoroughly before submitting. Not a language expert? Check out Scribbr’s professional proofreading services !

This article has been adapted into lecture slides that you can use to teach your students about writing a literature review.

Scribbr slides are free to use, customize, and distribute for educational purposes.

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If you want to know more about the research process , methodology , research bias , or statistics , make sure to check out some of our other articles with explanations and examples.

  • Sampling methods
  • Simple random sampling
  • Stratified sampling
  • Cluster sampling
  • Likert scales
  • Reproducibility

 Statistics

  • Null hypothesis
  • Statistical power
  • Probability distribution
  • Effect size
  • Poisson distribution

Research bias

  • Optimism bias
  • Cognitive bias
  • Implicit bias
  • Hawthorne effect
  • Anchoring bias
  • Explicit bias

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a thesis, dissertation , or research paper , in order to situate your work in relation to existing knowledge.

There are several reasons to conduct a literature review at the beginning of a research project:

  • To familiarize yourself with the current state of knowledge on your topic
  • To ensure that you’re not just repeating what others have already done
  • To identify gaps in knowledge and unresolved problems that your research can address
  • To develop your theoretical framework and methodology
  • To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

The literature review usually comes near the beginning of your thesis or dissertation . After the introduction , it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology .

A literature review is a survey of credible sources on a topic, often used in dissertations , theses, and research papers . Literature reviews give an overview of knowledge on a subject, helping you identify relevant theories and methods, as well as gaps in existing research. Literature reviews are set up similarly to other  academic texts , with an introduction , a main body, and a conclusion .

An  annotated bibliography is a list of  source references that has a short description (called an annotation ) for each of the sources. It is often assigned as part of the research process for a  paper .  

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  • UConn Library
  • Literature Review: The What, Why and How-to Guide
  • Introduction

Literature Review: The What, Why and How-to Guide — Introduction

  • Getting Started
  • How to Pick a Topic
  • Strategies to Find Sources
  • Evaluating Sources & Lit. Reviews
  • Tips for Writing Literature Reviews
  • Writing Literature Review: Useful Sites
  • Citation Resources
  • Other Academic Writings

What are Literature Reviews?

So, what is a literature review? "A literature review is an account of what has been published on a topic by accredited scholars and researchers. In writing the literature review, your purpose is to convey to your reader what knowledge and ideas have been established on a topic, and what their strengths and weaknesses are. As a piece of writing, the literature review must be defined by a guiding concept (e.g., your research objective, the problem or issue you are discussing, or your argumentative thesis). It is not just a descriptive list of the material available, or a set of summaries." Taylor, D.  The literature review: A few tips on conducting it . University of Toronto Health Sciences Writing Centre.

Goals of Literature Reviews

What are the goals of creating a Literature Review?  A literature could be written to accomplish different aims:

  • To develop a theory or evaluate an existing theory
  • To summarize the historical or existing state of a research topic
  • Identify a problem in a field of research 

Baumeister, R. F., & Leary, M. R. (1997). Writing narrative literature reviews .  Review of General Psychology , 1 (3), 311-320.

What kinds of sources require a Literature Review?

  • A research paper assigned in a course
  • A thesis or dissertation
  • A grant proposal
  • An article intended for publication in a journal

All these instances require you to collect what has been written about your research topic so that you can demonstrate how your own research sheds new light on the topic.

Types of Literature Reviews

What kinds of literature reviews are written?

Narrative review: The purpose of this type of review is to describe the current state of the research on a specific topic/research and to offer a critical analysis of the literature reviewed. Studies are grouped by research/theoretical categories, and themes and trends, strengths and weakness, and gaps are identified. The review ends with a conclusion section which summarizes the findings regarding the state of the research of the specific study, the gaps identify and if applicable, explains how the author's research will address gaps identify in the review and expand the knowledge on the topic reviewed.

  • Example : Predictors and Outcomes of U.S. Quality Maternity Leave: A Review and Conceptual Framework:  10.1177/08948453211037398  

Systematic review : "The authors of a systematic review use a specific procedure to search the research literature, select the studies to include in their review, and critically evaluate the studies they find." (p. 139). Nelson, L. K. (2013). Research in Communication Sciences and Disorders . Plural Publishing.

  • Example : The effect of leave policies on increasing fertility: a systematic review:  10.1057/s41599-022-01270-w

Meta-analysis : "Meta-analysis is a method of reviewing research findings in a quantitative fashion by transforming the data from individual studies into what is called an effect size and then pooling and analyzing this information. The basic goal in meta-analysis is to explain why different outcomes have occurred in different studies." (p. 197). Roberts, M. C., & Ilardi, S. S. (2003). Handbook of Research Methods in Clinical Psychology . Blackwell Publishing.

  • Example : Employment Instability and Fertility in Europe: A Meta-Analysis:  10.1215/00703370-9164737

Meta-synthesis : "Qualitative meta-synthesis is a type of qualitative study that uses as data the findings from other qualitative studies linked by the same or related topic." (p.312). Zimmer, L. (2006). Qualitative meta-synthesis: A question of dialoguing with texts .  Journal of Advanced Nursing , 53 (3), 311-318.

  • Example : Women’s perspectives on career successes and barriers: A qualitative meta-synthesis:  10.1177/05390184221113735

Literature Reviews in the Health Sciences

  • UConn Health subject guide on systematic reviews Explanation of the different review types used in health sciences literature as well as tools to help you find the right review type
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How to Write a Literature Review

What is a literature review.

  • What Is the Literature
  • Writing the Review

A literature review is much more than an annotated bibliography or a list of separate reviews of articles and books. It is a critical, analytical summary and synthesis of the current knowledge of a topic. Thus it should compare and relate different theories, findings, etc, rather than just summarize them individually. In addition, it should have a particular focus or theme to organize the review. It does not have to be an exhaustive account of everything published on the topic, but it should discuss all the significant academic literature and other relevant sources important for that focus.

This is meant to be a general guide to writing a literature review: ways to structure one, what to include, how it supplements other research. For more specific help on writing a review, and especially for help on finding the literature to review, sign up for a Personal Research Session .

The specific organization of a literature review depends on the type and purpose of the review, as well as on the specific field or topic being reviewed. But in general, it is a relatively brief but thorough exploration of past and current work on a topic. Rather than a chronological listing of previous work, though, literature reviews are usually organized thematically, such as different theoretical approaches, methodologies, or specific issues or concepts involved in the topic. A thematic organization makes it much easier to examine contrasting perspectives, theoretical approaches, methodologies, findings, etc, and to analyze the strengths and weaknesses of, and point out any gaps in, previous research. And this is the heart of what a literature review is about. A literature review may offer new interpretations, theoretical approaches, or other ideas; if it is part of a research proposal or report it should demonstrate the relationship of the proposed or reported research to others' work; but whatever else it does, it must provide a critical overview of the current state of research efforts. 

Literature reviews are common and very important in the sciences and social sciences. They are less common and have a less important role in the humanities, but they do have a place, especially stand-alone reviews.

Types of Literature Reviews

There are different types of literature reviews, and different purposes for writing a review, but the most common are:

  • Stand-alone literature review articles . These provide an overview and analysis of the current state of research on a topic or question. The goal is to evaluate and compare previous research on a topic to provide an analysis of what is currently known, and also to reveal controversies, weaknesses, and gaps in current work, thus pointing to directions for future research. You can find examples published in any number of academic journals, but there is a series of Annual Reviews of *Subject* which are specifically devoted to literature review articles. Writing a stand-alone review is often an effective way to get a good handle on a topic and to develop ideas for your own research program. For example, contrasting theoretical approaches or conflicting interpretations of findings can be the basis of your research project: can you find evidence supporting one interpretation against another, or can you propose an alternative interpretation that overcomes their limitations?
  • Part of a research proposal . This could be a proposal for a PhD dissertation, a senior thesis, or a class project. It could also be a submission for a grant. The literature review, by pointing out the current issues and questions concerning a topic, is a crucial part of demonstrating how your proposed research will contribute to the field, and thus of convincing your thesis committee to allow you to pursue the topic of your interest or a funding agency to pay for your research efforts.
  • Part of a research report . When you finish your research and write your thesis or paper to present your findings, it should include a literature review to provide the context to which your work is a contribution. Your report, in addition to detailing the methods, results, etc. of your research, should show how your work relates to others' work.

A literature review for a research report is often a revision of the review for a research proposal, which can be a revision of a stand-alone review. Each revision should be a fairly extensive revision. With the increased knowledge of and experience in the topic as you proceed, your understanding of the topic will increase. Thus, you will be in a better position to analyze and critique the literature. In addition, your focus will change as you proceed in your research. Some areas of the literature you initially reviewed will be marginal or irrelevant for your eventual research, and you will need to explore other areas more thoroughly. 

Examples of Literature Reviews

See the series of Annual Reviews of *Subject* which are specifically devoted to literature review articles to find many examples of stand-alone literature reviews in the biomedical, physical, and social sciences. 

Research report articles vary in how they are organized, but a common general structure is to have sections such as:

  • Abstract - Brief summary of the contents of the article
  • Introduction - A explanation of the purpose of the study, a statement of the research question(s) the study intends to address
  • Literature review - A critical assessment of the work done so far on this topic, to show how the current study relates to what has already been done
  • Methods - How the study was carried out (e.g. instruments or equipment, procedures, methods to gather and analyze data)
  • Results - What was found in the course of the study
  • Discussion - What do the results mean
  • Conclusion - State the conclusions and implications of the results, and discuss how it relates to the work reviewed in the literature review; also, point to directions for further work in the area

Here are some articles that illustrate variations on this theme. There is no need to read the entire articles (unless the contents interest you); just quickly browse through to see the sections, and see how each section is introduced and what is contained in them.

The Determinants of Undergraduate Grade Point Average: The Relative Importance of Family Background, High School Resources, and Peer Group Effects , in The Journal of Human Resources , v. 34 no. 2 (Spring 1999), p. 268-293.

This article has a standard breakdown of sections:

  • Introduction
  • Literature Review
  • Some discussion sections

First Encounters of the Bureaucratic Kind: Early Freshman Experiences with a Campus Bureaucracy , in The Journal of Higher Education , v. 67 no. 6 (Nov-Dec 1996), p. 660-691.

This one does not have a section specifically labeled as a "literature review" or "review of the literature," but the first few sections cite a long list of other sources discussing previous research in the area before the authors present their own study they are reporting.

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  • Last Updated: Jan 11, 2024 9:48 AM
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  • What is a Literature Review? | Guide, Template, & Examples

What is a Literature Review? | Guide, Template, & Examples

Published on 22 February 2022 by Shona McCombes . Revised on 7 June 2022.

What is a literature review? A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research.

There are five key steps to writing a literature review:

  • Search for relevant literature
  • Evaluate sources
  • Identify themes, debates and gaps
  • Outline the structure
  • Write your literature review

A good literature review doesn’t just summarise sources – it analyses, synthesises, and critically evaluates to give a clear picture of the state of knowledge on the subject.

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Table of contents

Why write a literature review, examples of literature reviews, step 1: search for relevant literature, step 2: evaluate and select sources, step 3: identify themes, debates and gaps, step 4: outline your literature review’s structure, step 5: write your literature review, frequently asked questions about literature reviews, introduction.

  • Quick Run-through
  • Step 1 & 2

When you write a dissertation or thesis, you will have to conduct a literature review to situate your research within existing knowledge. The literature review gives you a chance to:

  • Demonstrate your familiarity with the topic and scholarly context
  • Develop a theoretical framework and methodology for your research
  • Position yourself in relation to other researchers and theorists
  • Show how your dissertation addresses a gap or contributes to a debate

You might also have to write a literature review as a stand-alone assignment. In this case, the purpose is to evaluate the current state of research and demonstrate your knowledge of scholarly debates around a topic.

The content will look slightly different in each case, but the process of conducting a literature review follows the same steps. We’ve written a step-by-step guide that you can follow below.

Literature review guide

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Writing literature reviews can be quite challenging! A good starting point could be to look at some examples, depending on what kind of literature review you’d like to write.

  • Example literature review #1: “Why Do People Migrate? A Review of the Theoretical Literature” ( Theoretical literature review about the development of economic migration theory from the 1950s to today.)
  • Example literature review #2: “Literature review as a research methodology: An overview and guidelines” ( Methodological literature review about interdisciplinary knowledge acquisition and production.)
  • Example literature review #3: “The Use of Technology in English Language Learning: A Literature Review” ( Thematic literature review about the effects of technology on language acquisition.)
  • Example literature review #4: “Learners’ Listening Comprehension Difficulties in English Language Learning: A Literature Review” ( Chronological literature review about how the concept of listening skills has changed over time.)

You can also check out our templates with literature review examples and sample outlines at the links below.

Download Word doc Download Google doc

Before you begin searching for literature, you need a clearly defined topic .

If you are writing the literature review section of a dissertation or research paper, you will search for literature related to your research objectives and questions .

If you are writing a literature review as a stand-alone assignment, you will have to choose a focus and develop a central question to direct your search. Unlike a dissertation research question, this question has to be answerable without collecting original data. You should be able to answer it based only on a review of existing publications.

Make a list of keywords

Start by creating a list of keywords related to your research topic. Include each of the key concepts or variables you’re interested in, and list any synonyms and related terms. You can add to this list if you discover new keywords in the process of your literature search.

  • Social media, Facebook, Instagram, Twitter, Snapchat, TikTok
  • Body image, self-perception, self-esteem, mental health
  • Generation Z, teenagers, adolescents, youth

Search for relevant sources

Use your keywords to begin searching for sources. Some databases to search for journals and articles include:

  • Your university’s library catalogue
  • Google Scholar
  • Project Muse (humanities and social sciences)
  • Medline (life sciences and biomedicine)
  • EconLit (economics)
  • Inspec (physics, engineering and computer science)

You can use boolean operators to help narrow down your search:

Read the abstract to find out whether an article is relevant to your question. When you find a useful book or article, you can check the bibliography to find other relevant sources.

To identify the most important publications on your topic, take note of recurring citations. If the same authors, books or articles keep appearing in your reading, make sure to seek them out.

You probably won’t be able to read absolutely everything that has been written on the topic – you’ll have to evaluate which sources are most relevant to your questions.

For each publication, ask yourself:

  • What question or problem is the author addressing?
  • What are the key concepts and how are they defined?
  • What are the key theories, models and methods? Does the research use established frameworks or take an innovative approach?
  • What are the results and conclusions of the study?
  • How does the publication relate to other literature in the field? Does it confirm, add to, or challenge established knowledge?
  • How does the publication contribute to your understanding of the topic? What are its key insights and arguments?
  • What are the strengths and weaknesses of the research?

Make sure the sources you use are credible, and make sure you read any landmark studies and major theories in your field of research.

You can find out how many times an article has been cited on Google Scholar – a high citation count means the article has been influential in the field, and should certainly be included in your literature review.

The scope of your review will depend on your topic and discipline: in the sciences you usually only review recent literature, but in the humanities you might take a long historical perspective (for example, to trace how a concept has changed in meaning over time).

Remember that you can use our template to summarise and evaluate sources you’re thinking about using!

Take notes and cite your sources

As you read, you should also begin the writing process. Take notes that you can later incorporate into the text of your literature review.

It’s important to keep track of your sources with references to avoid plagiarism . It can be helpful to make an annotated bibliography, where you compile full reference information and write a paragraph of summary and analysis for each source. This helps you remember what you read and saves time later in the process.

You can use our free APA Reference Generator for quick, correct, consistent citations.

Prevent plagiarism, run a free check.

To begin organising your literature review’s argument and structure, you need to understand the connections and relationships between the sources you’ve read. Based on your reading and notes, you can look for:

  • Trends and patterns (in theory, method or results): do certain approaches become more or less popular over time?
  • Themes: what questions or concepts recur across the literature?
  • Debates, conflicts and contradictions: where do sources disagree?
  • Pivotal publications: are there any influential theories or studies that changed the direction of the field?
  • Gaps: what is missing from the literature? Are there weaknesses that need to be addressed?

This step will help you work out the structure of your literature review and (if applicable) show how your own research will contribute to existing knowledge.

  • Most research has focused on young women.
  • There is an increasing interest in the visual aspects of social media.
  • But there is still a lack of robust research on highly-visual platforms like Instagram and Snapchat – this is a gap that you could address in your own research.

There are various approaches to organising the body of a literature review. You should have a rough idea of your strategy before you start writing.

Depending on the length of your literature review, you can combine several of these strategies (for example, your overall structure might be thematic, but each theme is discussed chronologically).

Chronological

The simplest approach is to trace the development of the topic over time. However, if you choose this strategy, be careful to avoid simply listing and summarising sources in order.

Try to analyse patterns, turning points and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred.

If you have found some recurring central themes, you can organise your literature review into subsections that address different aspects of the topic.

For example, if you are reviewing literature about inequalities in migrant health outcomes, key themes might include healthcare policy, language barriers, cultural attitudes, legal status, and economic access.

Methodological

If you draw your sources from different disciplines or fields that use a variety of research methods , you might want to compare the results and conclusions that emerge from different approaches. For example:

  • Look at what results have emerged in qualitative versus quantitative research
  • Discuss how the topic has been approached by empirical versus theoretical scholarship
  • Divide the literature into sociological, historical, and cultural sources

Theoretical

A literature review is often the foundation for a theoretical framework . You can use it to discuss various theories, models, and definitions of key concepts.

You might argue for the relevance of a specific theoretical approach, or combine various theoretical concepts to create a framework for your research.

Like any other academic text, your literature review should have an introduction , a main body, and a conclusion . What you include in each depends on the objective of your literature review.

The introduction should clearly establish the focus and purpose of the literature review.

If you are writing the literature review as part of your dissertation or thesis, reiterate your central problem or research question and give a brief summary of the scholarly context. You can emphasise the timeliness of the topic (“many recent studies have focused on the problem of x”) or highlight a gap in the literature (“while there has been much research on x, few researchers have taken y into consideration”).

Depending on the length of your literature review, you might want to divide the body into subsections. You can use a subheading for each theme, time period, or methodological approach.

As you write, make sure to follow these tips:

  • Summarise and synthesise: give an overview of the main points of each source and combine them into a coherent whole.
  • Analyse and interpret: don’t just paraphrase other researchers – add your own interpretations, discussing the significance of findings in relation to the literature as a whole.
  • Critically evaluate: mention the strengths and weaknesses of your sources.
  • Write in well-structured paragraphs: use transitions and topic sentences to draw connections, comparisons and contrasts.

In the conclusion, you should summarise the key findings you have taken from the literature and emphasise their significance.

If the literature review is part of your dissertation or thesis, reiterate how your research addresses gaps and contributes new knowledge, or discuss how you have drawn on existing theories and methods to build a framework for your research. This can lead directly into your methodology section.

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a dissertation , thesis, research paper , or proposal .

There are several reasons to conduct a literature review at the beginning of a research project:

  • To familiarise yourself with the current state of knowledge on your topic
  • To ensure that you’re not just repeating what others have already done
  • To identify gaps in knowledge and unresolved problems that your research can address
  • To develop your theoretical framework and methodology
  • To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

The literature review usually comes near the beginning of your  dissertation . After the introduction , it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology .

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  • Correction 09 December 2020

How to write a superb literature review

Andy Tay is a freelance writer based in Singapore.

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Literature reviews are important resources for scientists. They provide historical context for a field while offering opinions on its future trajectory. Creating them can provide inspiration for one’s own research, as well as some practice in writing. But few scientists are trained in how to write a review — or in what constitutes an excellent one. Even picking the appropriate software to use can be an involved decision (see ‘Tools and techniques’). So Nature asked editors and working scientists with well-cited reviews for their tips.

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doi: https://doi.org/10.1038/d41586-020-03422-x

Interviews have been edited for length and clarity.

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Correction 09 December 2020 : An earlier version of the tables in this article included some incorrect details about the programs Zotero, Endnote and Manubot. These have now been corrected.

Hsing, I.-M., Xu, Y. & Zhao, W. Electroanalysis 19 , 755–768 (2007).

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Ledesma, H. A. et al. Nature Nanotechnol. 14 , 645–657 (2019).

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Brahlek, M., Koirala, N., Bansal, N. & Oh, S. Solid State Commun. 215–216 , 54–62 (2015).

Choi, Y. & Lee, S. Y. Nature Rev. Chem . https://doi.org/10.1038/s41570-020-00221-w (2020).

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What is a Literature Review?

So, what is a literature review .

"A literature review is an account of what has been published on a topic by accredited scholars and researchers. In writing the literature review, your purpose is to convey to your reader what knowledge and ideas have been established on a topic, and what their strengths and weaknesses are. As a piece of writing, the literature review must be defined by a guiding concept (e.g., your research objective, the problem or issue you are discussing, or your argumentative thesis). It is not just a descriptive list of the material available or a set of summaries." - Quote from Taylor, D. (n.d)."The Literature Review: A Few Tips on Conducting it".

  • Citation: "The Literature Review: A Few Tips on Conducting it"

What kinds of literature reviews are written?

Each field has a particular way to do reviews for academic research literature. In the social sciences and humanities the most common are:

  • Narrative Reviews: The purpose of this type of review is to describe the current state of the research on a specific research topic and to offer a critical analysis of the literature reviewed. Studies are grouped by research/theoretical categories, and themes and trends, strengths and weaknesses, and gaps are identified. The review ends with a conclusion section that summarizes the findings regarding the state of the research of the specific study, the gaps identify and if applicable, explains how the author's research will address gaps identify in the review and expand the knowledge on the topic reviewed.
  • Book review essays/ Historiographical review essays : A type of literature review typical in History and related fields, e.g., Latin American studies. For example, the Latin American Research Review explains that the purpose of this type of review is to “(1) to familiarize readers with the subject, approach, arguments, and conclusions found in a group of books whose common focus is a historical period; a country or region within Latin America; or a practice, development, or issue of interest to specialists and others; (2) to locate these books within current scholarship, critical methodologies, and approaches; and (3) to probe the relation of these new books to previous work on the subject, especially canonical texts. Unlike individual book reviews, the cluster reviews found in LARR seek to address the state of the field or discipline and not solely the works at issue.” - LARR

What are the Goals of Creating a Literature Review?

  • To develop a theory or evaluate an existing theory
  • To summarize the historical or existing state of a research topic
  • Identify a problem in a field of research 
  • Baumeister, R.F. & Leary, M.R. (1997). "Writing narrative literature reviews," Review of General Psychology , 1(3), 311-320.

When do you need to write a Literature Review?

  • When writing a prospectus or a thesis/dissertation
  • When writing a research paper
  • When writing a grant proposal

In all these cases you need to dedicate a chapter in these works to showcase what has been written about your research topic and to point out how your own research will shed new light into a body of scholarship.

Where I can find examples of Literature Reviews?

Note:  In the humanities, even if they don't use the term "literature review", they may have a dedicated  chapter that reviewed the "critical bibliography" or they incorporated that review in the introduction or first chapter of the dissertation, book, or article.

  • UCSB electronic theses and dissertations In partnership with the Graduate Division, the UC Santa Barbara Library is making available theses and dissertations produced by UCSB students. Currently included in ADRL are theses and dissertations that were originally filed electronically, starting in 2011. In future phases of ADRL, all theses and dissertations created by UCSB students may be digitized and made available.

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Where to Find Standalone Literature Reviews

Literature reviews are also written as standalone articles as a way to survey a particular research topic in-depth. This type of literature review looks at a topic from a historical perspective to see how the understanding of the topic has changed over time. 

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A literature review surveys prior research published in books, scholarly articles, and any other sources relevant to a particular issue, area of research, or theory, and by so doing, provides a description, summary, and critical evaluation of these works in relation to the research problem being investigated. Literature reviews are designed to provide an overview of sources you have used in researching a particular topic and to demonstrate to your readers how your research fits within existing scholarship about the topic.

Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . Fourth edition. Thousand Oaks, CA: SAGE, 2014.

Importance of a Good Literature Review

A literature review may consist of simply a summary of key sources, but in the social sciences, a literature review usually has an organizational pattern and combines both summary and synthesis, often within specific conceptual categories . A summary is a recap of the important information of the source, but a synthesis is a re-organization, or a reshuffling, of that information in a way that informs how you are planning to investigate a research problem. The analytical features of a literature review might:

  • Give a new interpretation of old material or combine new with old interpretations,
  • Trace the intellectual progression of the field, including major debates,
  • Depending on the situation, evaluate the sources and advise the reader on the most pertinent or relevant research, or
  • Usually in the conclusion of a literature review, identify where gaps exist in how a problem has been researched to date.

Given this, the purpose of a literature review is to:

  • Place each work in the context of its contribution to understanding the research problem being studied.
  • Describe the relationship of each work to the others under consideration.
  • Identify new ways to interpret prior research.
  • Reveal any gaps that exist in the literature.
  • Resolve conflicts amongst seemingly contradictory previous studies.
  • Identify areas of prior scholarship to prevent duplication of effort.
  • Point the way in fulfilling a need for additional research.
  • Locate your own research within the context of existing literature [very important].

Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper. 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Jesson, Jill. Doing Your Literature Review: Traditional and Systematic Techniques . Los Angeles, CA: SAGE, 2011; Knopf, Jeffrey W. "Doing a Literature Review." PS: Political Science and Politics 39 (January 2006): 127-132; Ridley, Diana. The Literature Review: A Step-by-Step Guide for Students . 2nd ed. Los Angeles, CA: SAGE, 2012.

Types of Literature Reviews

It is important to think of knowledge in a given field as consisting of three layers. First, there are the primary studies that researchers conduct and publish. Second are the reviews of those studies that summarize and offer new interpretations built from and often extending beyond the primary studies. Third, there are the perceptions, conclusions, opinion, and interpretations that are shared informally among scholars that become part of the body of epistemological traditions within the field.

In composing a literature review, it is important to note that it is often this third layer of knowledge that is cited as "true" even though it often has only a loose relationship to the primary studies and secondary literature reviews. Given this, while literature reviews are designed to provide an overview and synthesis of pertinent sources you have explored, there are a number of approaches you could adopt depending upon the type of analysis underpinning your study.

Argumentative Review This form examines literature selectively in order to support or refute an argument, deeply embedded assumption, or philosophical problem already established in the literature. The purpose is to develop a body of literature that establishes a contrarian viewpoint. Given the value-laden nature of some social science research [e.g., educational reform; immigration control], argumentative approaches to analyzing the literature can be a legitimate and important form of discourse. However, note that they can also introduce problems of bias when they are used to make summary claims of the sort found in systematic reviews [see below].

Integrative Review Considered a form of research that reviews, critiques, and synthesizes representative literature on a topic in an integrated way such that new frameworks and perspectives on the topic are generated. The body of literature includes all studies that address related or identical hypotheses or research problems. A well-done integrative review meets the same standards as primary research in regard to clarity, rigor, and replication. This is the most common form of review in the social sciences.

Historical Review Few things rest in isolation from historical precedent. Historical literature reviews focus on examining research throughout a period of time, often starting with the first time an issue, concept, theory, phenomena emerged in the literature, then tracing its evolution within the scholarship of a discipline. The purpose is to place research in a historical context to show familiarity with state-of-the-art developments and to identify the likely directions for future research.

Methodological Review A review does not always focus on what someone said [findings], but how they came about saying what they say [method of analysis]. Reviewing methods of analysis provides a framework of understanding at different levels [i.e. those of theory, substantive fields, research approaches, and data collection and analysis techniques], how researchers draw upon a wide variety of knowledge ranging from the conceptual level to practical documents for use in fieldwork in the areas of ontological and epistemological consideration, quantitative and qualitative integration, sampling, interviewing, data collection, and data analysis. This approach helps highlight ethical issues which you should be aware of and consider as you go through your own study.

Systematic Review This form consists of an overview of existing evidence pertinent to a clearly formulated research question, which uses pre-specified and standardized methods to identify and critically appraise relevant research, and to collect, report, and analyze data from the studies that are included in the review. The goal is to deliberately document, critically evaluate, and summarize scientifically all of the research about a clearly defined research problem . Typically it focuses on a very specific empirical question, often posed in a cause-and-effect form, such as "To what extent does A contribute to B?" This type of literature review is primarily applied to examining prior research studies in clinical medicine and allied health fields, but it is increasingly being used in the social sciences.

Theoretical Review The purpose of this form is to examine the corpus of theory that has accumulated in regard to an issue, concept, theory, phenomena. The theoretical literature review helps to establish what theories already exist, the relationships between them, to what degree the existing theories have been investigated, and to develop new hypotheses to be tested. Often this form is used to help establish a lack of appropriate theories or reveal that current theories are inadequate for explaining new or emerging research problems. The unit of analysis can focus on a theoretical concept or a whole theory or framework.

NOTE: Most often the literature review will incorporate some combination of types. For example, a review that examines literature supporting or refuting an argument, assumption, or philosophical problem related to the research problem will also need to include writing supported by sources that establish the history of these arguments in the literature.

Baumeister, Roy F. and Mark R. Leary. "Writing Narrative Literature Reviews."  Review of General Psychology 1 (September 1997): 311-320; Mark R. Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Kennedy, Mary M. "Defining a Literature." Educational Researcher 36 (April 2007): 139-147; Petticrew, Mark and Helen Roberts. Systematic Reviews in the Social Sciences: A Practical Guide . Malden, MA: Blackwell Publishers, 2006; Torracro, Richard. "Writing Integrative Literature Reviews: Guidelines and Examples." Human Resource Development Review 4 (September 2005): 356-367; Rocco, Tonette S. and Maria S. Plakhotnik. "Literature Reviews, Conceptual Frameworks, and Theoretical Frameworks: Terms, Functions, and Distinctions." Human Ressource Development Review 8 (March 2008): 120-130; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016.

Structure and Writing Style

I.  Thinking About Your Literature Review

The structure of a literature review should include the following in support of understanding the research problem :

  • An overview of the subject, issue, or theory under consideration, along with the objectives of the literature review,
  • Division of works under review into themes or categories [e.g. works that support a particular position, those against, and those offering alternative approaches entirely],
  • An explanation of how each work is similar to and how it varies from the others,
  • Conclusions as to which pieces are best considered in their argument, are most convincing of their opinions, and make the greatest contribution to the understanding and development of their area of research.

The critical evaluation of each work should consider :

  • Provenance -- what are the author's credentials? Are the author's arguments supported by evidence [e.g. primary historical material, case studies, narratives, statistics, recent scientific findings]?
  • Methodology -- were the techniques used to identify, gather, and analyze the data appropriate to addressing the research problem? Was the sample size appropriate? Were the results effectively interpreted and reported?
  • Objectivity -- is the author's perspective even-handed or prejudicial? Is contrary data considered or is certain pertinent information ignored to prove the author's point?
  • Persuasiveness -- which of the author's theses are most convincing or least convincing?
  • Validity -- are the author's arguments and conclusions convincing? Does the work ultimately contribute in any significant way to an understanding of the subject?

II.  Development of the Literature Review

Four Basic Stages of Writing 1.  Problem formulation -- which topic or field is being examined and what are its component issues? 2.  Literature search -- finding materials relevant to the subject being explored. 3.  Data evaluation -- determining which literature makes a significant contribution to the understanding of the topic. 4.  Analysis and interpretation -- discussing the findings and conclusions of pertinent literature.

Consider the following issues before writing the literature review: Clarify If your assignment is not specific about what form your literature review should take, seek clarification from your professor by asking these questions: 1.  Roughly how many sources would be appropriate to include? 2.  What types of sources should I review (books, journal articles, websites; scholarly versus popular sources)? 3.  Should I summarize, synthesize, or critique sources by discussing a common theme or issue? 4.  Should I evaluate the sources in any way beyond evaluating how they relate to understanding the research problem? 5.  Should I provide subheadings and other background information, such as definitions and/or a history? Find Models Use the exercise of reviewing the literature to examine how authors in your discipline or area of interest have composed their literature review sections. Read them to get a sense of the types of themes you might want to look for in your own research or to identify ways to organize your final review. The bibliography or reference section of sources you've already read, such as required readings in the course syllabus, are also excellent entry points into your own research. Narrow the Topic The narrower your topic, the easier it will be to limit the number of sources you need to read in order to obtain a good survey of relevant resources. Your professor will probably not expect you to read everything that's available about the topic, but you'll make the act of reviewing easier if you first limit scope of the research problem. A good strategy is to begin by searching the USC Libraries Catalog for recent books about the topic and review the table of contents for chapters that focuses on specific issues. You can also review the indexes of books to find references to specific issues that can serve as the focus of your research. For example, a book surveying the history of the Israeli-Palestinian conflict may include a chapter on the role Egypt has played in mediating the conflict, or look in the index for the pages where Egypt is mentioned in the text. Consider Whether Your Sources are Current Some disciplines require that you use information that is as current as possible. This is particularly true in disciplines in medicine and the sciences where research conducted becomes obsolete very quickly as new discoveries are made. However, when writing a review in the social sciences, a survey of the history of the literature may be required. In other words, a complete understanding the research problem requires you to deliberately examine how knowledge and perspectives have changed over time. Sort through other current bibliographies or literature reviews in the field to get a sense of what your discipline expects. You can also use this method to explore what is considered by scholars to be a "hot topic" and what is not.

III.  Ways to Organize Your Literature Review

Chronology of Events If your review follows the chronological method, you could write about the materials according to when they were published. This approach should only be followed if a clear path of research building on previous research can be identified and that these trends follow a clear chronological order of development. For example, a literature review that focuses on continuing research about the emergence of German economic power after the fall of the Soviet Union. By Publication Order your sources by publication chronology, then, only if the order demonstrates a more important trend. For instance, you could order a review of literature on environmental studies of brown fields if the progression revealed, for example, a change in the soil collection practices of the researchers who wrote and/or conducted the studies. Thematic [“conceptual categories”] A thematic literature review is the most common approach to summarizing prior research in the social and behavioral sciences. Thematic reviews are organized around a topic or issue, rather than the progression of time, although the progression of time may still be incorporated into a thematic review. For example, a review of the Internet’s impact on American presidential politics could focus on the development of online political satire. While the study focuses on one topic, the Internet’s impact on American presidential politics, it would still be organized chronologically reflecting technological developments in media. The difference in this example between a "chronological" and a "thematic" approach is what is emphasized the most: themes related to the role of the Internet in presidential politics. Note that more authentic thematic reviews tend to break away from chronological order. A review organized in this manner would shift between time periods within each section according to the point being made. Methodological A methodological approach focuses on the methods utilized by the researcher. For the Internet in American presidential politics project, one methodological approach would be to look at cultural differences between the portrayal of American presidents on American, British, and French websites. Or the review might focus on the fundraising impact of the Internet on a particular political party. A methodological scope will influence either the types of documents in the review or the way in which these documents are discussed.

Other Sections of Your Literature Review Once you've decided on the organizational method for your literature review, the sections you need to include in the paper should be easy to figure out because they arise from your organizational strategy. In other words, a chronological review would have subsections for each vital time period; a thematic review would have subtopics based upon factors that relate to the theme or issue. However, sometimes you may need to add additional sections that are necessary for your study, but do not fit in the organizational strategy of the body. What other sections you include in the body is up to you. However, only include what is necessary for the reader to locate your study within the larger scholarship about the research problem.

Here are examples of other sections, usually in the form of a single paragraph, you may need to include depending on the type of review you write:

  • Current Situation : Information necessary to understand the current topic or focus of the literature review.
  • Sources Used : Describes the methods and resources [e.g., databases] you used to identify the literature you reviewed.
  • History : The chronological progression of the field, the research literature, or an idea that is necessary to understand the literature review, if the body of the literature review is not already a chronology.
  • Selection Methods : Criteria you used to select (and perhaps exclude) sources in your literature review. For instance, you might explain that your review includes only peer-reviewed [i.e., scholarly] sources.
  • Standards : Description of the way in which you present your information.
  • Questions for Further Research : What questions about the field has the review sparked? How will you further your research as a result of the review?

IV.  Writing Your Literature Review

Once you've settled on how to organize your literature review, you're ready to write each section. When writing your review, keep in mind these issues.

Use Evidence A literature review section is, in this sense, just like any other academic research paper. Your interpretation of the available sources must be backed up with evidence [citations] that demonstrates that what you are saying is valid. Be Selective Select only the most important points in each source to highlight in the review. The type of information you choose to mention should relate directly to the research problem, whether it is thematic, methodological, or chronological. Related items that provide additional information, but that are not key to understanding the research problem, can be included in a list of further readings . Use Quotes Sparingly Some short quotes are appropriate if you want to emphasize a point, or if what an author stated cannot be easily paraphrased. Sometimes you may need to quote certain terminology that was coined by the author, is not common knowledge, or taken directly from the study. Do not use extensive quotes as a substitute for using your own words in reviewing the literature. Summarize and Synthesize Remember to summarize and synthesize your sources within each thematic paragraph as well as throughout the review. Recapitulate important features of a research study, but then synthesize it by rephrasing the study's significance and relating it to your own work and the work of others. Keep Your Own Voice While the literature review presents others' ideas, your voice [the writer's] should remain front and center. For example, weave references to other sources into what you are writing but maintain your own voice by starting and ending the paragraph with your own ideas and wording. Use Caution When Paraphrasing When paraphrasing a source that is not your own, be sure to represent the author's information or opinions accurately and in your own words. Even when paraphrasing an author’s work, you still must provide a citation to that work.

V.  Common Mistakes to Avoid

These are the most common mistakes made in reviewing social science research literature.

  • Sources in your literature review do not clearly relate to the research problem;
  • You do not take sufficient time to define and identify the most relevant sources to use in the literature review related to the research problem;
  • Relies exclusively on secondary analytical sources rather than including relevant primary research studies or data;
  • Uncritically accepts another researcher's findings and interpretations as valid, rather than examining critically all aspects of the research design and analysis;
  • Does not describe the search procedures that were used in identifying the literature to review;
  • Reports isolated statistical results rather than synthesizing them in chi-squared or meta-analytic methods; and,
  • Only includes research that validates assumptions and does not consider contrary findings and alternative interpretations found in the literature.

Cook, Kathleen E. and Elise Murowchick. “Do Literature Review Skills Transfer from One Course to Another?” Psychology Learning and Teaching 13 (March 2014): 3-11; Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Jesson, Jill. Doing Your Literature Review: Traditional and Systematic Techniques . London: SAGE, 2011; Literature Review Handout. Online Writing Center. Liberty University; Literature Reviews. The Writing Center. University of North Carolina; Onwuegbuzie, Anthony J. and Rebecca Frels. Seven Steps to a Comprehensive Literature Review: A Multimodal and Cultural Approach . Los Angeles, CA: SAGE, 2016; Ridley, Diana. The Literature Review: A Step-by-Step Guide for Students . 2nd ed. Los Angeles, CA: SAGE, 2012; Randolph, Justus J. “A Guide to Writing the Dissertation Literature Review." Practical Assessment, Research, and Evaluation. vol. 14, June 2009; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016; Taylor, Dena. The Literature Review: A Few Tips On Conducting It. University College Writing Centre. University of Toronto; Writing a Literature Review. Academic Skills Centre. University of Canberra.

Writing Tip

Break Out of Your Disciplinary Box!

Thinking interdisciplinarily about a research problem can be a rewarding exercise in applying new ideas, theories, or concepts to an old problem. For example, what might cultural anthropologists say about the continuing conflict in the Middle East? In what ways might geographers view the need for better distribution of social service agencies in large cities than how social workers might study the issue? You don’t want to substitute a thorough review of core research literature in your discipline for studies conducted in other fields of study. However, particularly in the social sciences, thinking about research problems from multiple vectors is a key strategy for finding new solutions to a problem or gaining a new perspective. Consult with a librarian about identifying research databases in other disciplines; almost every field of study has at least one comprehensive database devoted to indexing its research literature.

Frodeman, Robert. The Oxford Handbook of Interdisciplinarity . New York: Oxford University Press, 2010.

Another Writing Tip

Don't Just Review for Content!

While conducting a review of the literature, maximize the time you devote to writing this part of your paper by thinking broadly about what you should be looking for and evaluating. Review not just what scholars are saying, but how are they saying it. Some questions to ask:

  • How are they organizing their ideas?
  • What methods have they used to study the problem?
  • What theories have been used to explain, predict, or understand their research problem?
  • What sources have they cited to support their conclusions?
  • How have they used non-textual elements [e.g., charts, graphs, figures, etc.] to illustrate key points?

When you begin to write your literature review section, you'll be glad you dug deeper into how the research was designed and constructed because it establishes a means for developing more substantial analysis and interpretation of the research problem.

Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1 998.

Yet Another Writing Tip

When Do I Know I Can Stop Looking and Move On?

Here are several strategies you can utilize to assess whether you've thoroughly reviewed the literature:

  • Look for repeating patterns in the research findings . If the same thing is being said, just by different people, then this likely demonstrates that the research problem has hit a conceptual dead end. At this point consider: Does your study extend current research?  Does it forge a new path? Or, does is merely add more of the same thing being said?
  • Look at sources the authors cite to in their work . If you begin to see the same researchers cited again and again, then this is often an indication that no new ideas have been generated to address the research problem.
  • Search Google Scholar to identify who has subsequently cited leading scholars already identified in your literature review [see next sub-tab]. This is called citation tracking and there are a number of sources that can help you identify who has cited whom, particularly scholars from outside of your discipline. Here again, if the same authors are being cited again and again, this may indicate no new literature has been written on the topic.

Onwuegbuzie, Anthony J. and Rebecca Frels. Seven Steps to a Comprehensive Literature Review: A Multimodal and Cultural Approach . Los Angeles, CA: Sage, 2016; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016.

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What is a Literature Review?

A literature or narrative review is a comprehensive review and analysis of the published literature on a specific topic or research question. The literature that is reviewed contains: books, articles, academic articles, conference proceedings, association papers, and dissertations. It contains the most pertinent studies and points to important past and current research and practices. It provides background and context, and shows how your research will contribute to the field. 

A literature review should: 

  • Provide a comprehensive and updated review of the literature;
  • Explain why this review has taken place;
  • Articulate a position or hypothesis;
  • Acknowledge and account for conflicting and corroborating points of view

From  S age Research Methods

Purpose of a Literature Review

A literature review can be written as an introduction to a study to:

  • Demonstrate how a study fills a gap in research
  • Compare a study with other research that's been done

Or it can be a separate work (a research article on its own) which:

  • Organizes or describes a topic
  • Describes variables within a particular issue/problem

Limitations of a Literature Review

Some of the limitations of a literature review are:

  • It's a snapshot in time. Unlike other reviews, this one has beginning, a middle and an end. There may be future developments that could make your work less relevant.
  • It may be too focused. Some niche studies may miss the bigger picture.
  • It can be difficult to be comprehensive. There is no way to make sure all the literature on a topic was considered.
  • It is easy to be biased if you stick to top tier journals. There may be other places where people are publishing exemplary research. Look to open access publications and conferences to reflect a more inclusive collection. Also, make sure to include opposing views (and not just supporting evidence).

Source: Grant, Maria J., and Andrew Booth. “A Typology of Reviews: An Analysis of 14 Review Types and Associated Methodologies.” Health Information & Libraries Journal, vol. 26, no. 2, June 2009, pp. 91–108. Wiley Online Library, doi:10.1111/j.1471-1842.2009.00848.x.

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What is a literature review?

A literature review is an integrated analysis -- not just a summary-- of scholarly writings and other relevant evidence related directly to your research question.  That is, it represents a synthesis of the evidence that provides background information on your topic and shows a association between the evidence and your research question.

A literature review may be a stand alone work or the introduction to a larger research paper, depending on the assignment.  Rely heavily on the guidelines your instructor has given you.

Why is it important?

A literature review is important because it:

  • Explains the background of research on a topic.
  • Demonstrates why a topic is significant to a subject area.
  • Discovers relationships between research studies/ideas.
  • Identifies major themes, concepts, and researchers on a topic.
  • Identifies critical gaps and points of disagreement.
  • Discusses further research questions that logically come out of the previous studies.

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1. Choose a topic. Define your research question.

Your literature review should be guided by your central research question.  The literature represents background and research developments related to a specific research question, interpreted and analyzed by you in a synthesized way.

  • Make sure your research question is not too broad or too narrow.  Is it manageable?
  • Begin writing down terms that are related to your question. These will be useful for searches later.
  • If you have the opportunity, discuss your topic with your professor and your class mates.

2. Decide on the scope of your review

How many studies do you need to look at? How comprehensive should it be? How many years should it cover? 

  • This may depend on your assignment.  How many sources does the assignment require?

3. Select the databases you will use to conduct your searches.

Make a list of the databases you will search. 

Where to find databases:

  • use the tabs on this guide
  • Find other databases in the Nursing Information Resources web page
  • More on the Medical Library web page
  • ... and more on the Yale University Library web page

4. Conduct your searches to find the evidence. Keep track of your searches.

  • Use the key words in your question, as well as synonyms for those words, as terms in your search. Use the database tutorials for help.
  • Save the searches in the databases. This saves time when you want to redo, or modify, the searches. It is also helpful to use as a guide is the searches are not finding any useful results.
  • Review the abstracts of research studies carefully. This will save you time.
  • Use the bibliographies and references of research studies you find to locate others.
  • Check with your professor, or a subject expert in the field, if you are missing any key works in the field.
  • Ask your librarian for help at any time.
  • Use a citation manager, such as EndNote as the repository for your citations. See the EndNote tutorials for help.

Review the literature

Some questions to help you analyze the research:

  • What was the research question of the study you are reviewing? What were the authors trying to discover?
  • Was the research funded by a source that could influence the findings?
  • What were the research methodologies? Analyze its literature review, the samples and variables used, the results, and the conclusions.
  • Does the research seem to be complete? Could it have been conducted more soundly? What further questions does it raise?
  • If there are conflicting studies, why do you think that is?
  • How are the authors viewed in the field? Has this study been cited? If so, how has it been analyzed?

Tips: 

  • Review the abstracts carefully.  
  • Keep careful notes so that you may track your thought processes during the research process.
  • Create a matrix of the studies for easy analysis, and synthesis, across all of the studies.
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Literature Reviews

  • What is a Literature Review?
  • Steps for Creating a Literature Review
  • Providing Evidence / Critical Analysis
  • Challenges when writing a Literature Review
  • Systematic Literature Reviews

Developing a Literature Review

1. Purpose and Scope

To help you develop a literature review, gather information on existing research, sub-topics, relevant research, and overlaps. Note initial thoughts on the topic - a mind map or list might be helpful - and avoid unfocused reading, collecting irrelevant content.  A literature review serves to place your research within the context of existing knowledge. It demonstrates your understanding of the field and identifies gaps that your research aims to fill. This helps in justifying the relevance and necessity of your study.

To avoid over-reading, set a target word count for each section and limit reading time. Plan backwards from the deadline and move on to other parts of the investigation. Read major texts and explore up-to-date research. Check reference lists and citation indexes for common standard texts. Be guided by research questions and refocus on your topic when needed. Stop reading if you find similar viewpoints or if you're going off topic.

You can use a "Synthesis Matrix" to keep track of your reading notes. This concept map helps you to provide a summary of the literature and its connections is produced as a result of this study. Utilizing referencing software like RefWorks to obtain citations, you can construct the framework for composing your literature evaluation.

2. Source Selection

Focus on searching for academically authoritative texts such as academic books, journals, research reports, and government publications. These sources are critical for ensuring the credibility and reliability of your review. 

  • Academic Books: Provide comprehensive coverage of a topic.
  • Journal Articles: Offer the most up-to-date research and are essential for a literature review.
  • Research Reports: Detailed accounts of specific research projects.
  • Government Publications: Official documents that provide reliable data and insights.

3. Thematic Analysis

Instead of merely summarizing sources, identify and discuss key themes that emerge from the literature. This involves interpreting and evaluating how different authors have tackled similar issues and how their findings relate to your research.

4. Critical Evaluation

Adopt a critical attitude towards the sources you review. Scrutinize, question, and dissect the material to ensure that your review is not just descriptive but analytical. This helps in highlighting the significance of various sources and their relevance to your research.

Each work's critical assessment should take into account:

Provenance:  What qualifications does the author have? Are the author's claims backed up by proof, such as first-hand accounts from history, case studies, stories, statistics, and current scientific discoveries? Methodology:  Were the strategies employed to locate, collect, and evaluate the data suitable for tackling the study question? Was the sample size suitable? Were the findings properly reported and interpreted? Objectivity : Is the author's viewpoint impartial or biased? Does the author's thesis get supported by evidence that refutes it, or does it ignore certain important facts? Persuasiveness:  Which of the author's arguments is the strongest or weakest in terms of persuasiveness? Value:  Are the author's claims and deductions believable? Does the study ultimately advance our understanding of the issue in any meaningful way?

5. Categorization

Organize your literature review by grouping sources into categories based on themes, relevance to research questions, theoretical paradigms, or chronology. This helps in presenting your findings in a structured manner.

6. Source Validity

Ensure that the sources you include are valid and reliable. Classic texts may retain their authority over time, but for fields that evolve rapidly, prioritize the most recent research. Always check the credibility of the authors and the impact of their work in the field.

7. Synthesis and Findings

Synthesize the information from various sources to draw conclusions about the current state of knowledge. Identify trends, controversies, and gaps in the literature. Relate your findings to your research questions and suggest future directions for research.

Practical Tips

  • Use a variety of sources, including online databases, university libraries, and reference lists from relevant articles. This ensures a comprehensive coverage of the literature.
  • Avoid listing sources without analysis. Use tables, bulk citations, and footnotes to manage references efficiently and make your review more readable.
  • Writing a literature review is an ongoing process. Start writing early and revise as you read more. This iterative process helps in refining your arguments and identifying additional sources as needed.  

Brown University Library (2024) Organizing and Creating Information. Available at: https://libguides.brown.edu/organize/litreview (Accessed: 30 July 2024).

Pacheco-Vega, R. (2016) Synthesizing different bodies of work in your literature review: The Conceptual Synthesis Excel Dump (CSED) technique . Available at: http://www.raulpacheco.org/2016/06/synthesizing-different-bodies-of-work-in-your-literature-review-the-conceptual-synthesis-excel-dump-technique/ (Accessed: 30 July 2024).

Study Advice at the University of Reading (2024) Literature reviews . Available at: https://libguides.reading.ac.uk/literaturereview/developing (Accessed: 31 July 2024).

Further Reading

Frameworks for creating answerable (re)search questions  How to Guide

Literature Searching How to Guide

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The Writing Center • University of North Carolina at Chapel Hill

Literature Reviews

What this handout is about.

This handout will explain what literature reviews are and offer insights into the form and construction of literature reviews in the humanities, social sciences, and sciences.

Introduction

OK. You’ve got to write a literature review. You dust off a novel and a book of poetry, settle down in your chair, and get ready to issue a “thumbs up” or “thumbs down” as you leaf through the pages. “Literature review” done. Right?

Wrong! The “literature” of a literature review refers to any collection of materials on a topic, not necessarily the great literary texts of the world. “Literature” could be anything from a set of government pamphlets on British colonial methods in Africa to scholarly articles on the treatment of a torn ACL. And a review does not necessarily mean that your reader wants you to give your personal opinion on whether or not you liked these sources.

What is a literature review, then?

A literature review discusses published information in a particular subject area, and sometimes information in a particular subject area within a certain time period.

A literature review can be just a simple summary of the sources, but it usually has an organizational pattern and combines both summary and synthesis. A summary is a recap of the important information of the source, but a synthesis is a re-organization, or a reshuffling, of that information. It might give a new interpretation of old material or combine new with old interpretations. Or it might trace the intellectual progression of the field, including major debates. And depending on the situation, the literature review may evaluate the sources and advise the reader on the most pertinent or relevant.

But how is a literature review different from an academic research paper?

The main focus of an academic research paper is to develop a new argument, and a research paper is likely to contain a literature review as one of its parts. In a research paper, you use the literature as a foundation and as support for a new insight that you contribute. The focus of a literature review, however, is to summarize and synthesize the arguments and ideas of others without adding new contributions.

Why do we write literature reviews?

Literature reviews provide you with a handy guide to a particular topic. If you have limited time to conduct research, literature reviews can give you an overview or act as a stepping stone. For professionals, they are useful reports that keep them up to date with what is current in the field. For scholars, the depth and breadth of the literature review emphasizes the credibility of the writer in his or her field. Literature reviews also provide a solid background for a research paper’s investigation. Comprehensive knowledge of the literature of the field is essential to most research papers.

Who writes these things, anyway?

Literature reviews are written occasionally in the humanities, but mostly in the sciences and social sciences; in experiment and lab reports, they constitute a section of the paper. Sometimes a literature review is written as a paper in itself.

Let’s get to it! What should I do before writing the literature review?

If your assignment is not very specific, seek clarification from your instructor:

  • Roughly how many sources should you include?
  • What types of sources (books, journal articles, websites)?
  • Should you summarize, synthesize, or critique your sources by discussing a common theme or issue?
  • Should you evaluate your sources?
  • Should you provide subheadings and other background information, such as definitions and/or a history?

Find models

Look for other literature reviews in your area of interest or in the discipline and read them to get a sense of the types of themes you might want to look for in your own research or ways to organize your final review. You can simply put the word “review” in your search engine along with your other topic terms to find articles of this type on the Internet or in an electronic database. The bibliography or reference section of sources you’ve already read are also excellent entry points into your own research.

Narrow your topic

There are hundreds or even thousands of articles and books on most areas of study. The narrower your topic, the easier it will be to limit the number of sources you need to read in order to get a good survey of the material. Your instructor will probably not expect you to read everything that’s out there on the topic, but you’ll make your job easier if you first limit your scope.

Keep in mind that UNC Libraries have research guides and to databases relevant to many fields of study. You can reach out to the subject librarian for a consultation: https://library.unc.edu/support/consultations/ .

And don’t forget to tap into your professor’s (or other professors’) knowledge in the field. Ask your professor questions such as: “If you had to read only one book from the 90’s on topic X, what would it be?” Questions such as this help you to find and determine quickly the most seminal pieces in the field.

Consider whether your sources are current

Some disciplines require that you use information that is as current as possible. In the sciences, for instance, treatments for medical problems are constantly changing according to the latest studies. Information even two years old could be obsolete. However, if you are writing a review in the humanities, history, or social sciences, a survey of the history of the literature may be what is needed, because what is important is how perspectives have changed through the years or within a certain time period. Try sorting through some other current bibliographies or literature reviews in the field to get a sense of what your discipline expects. You can also use this method to consider what is currently of interest to scholars in this field and what is not.

Strategies for writing the literature review

Find a focus.

A literature review, like a term paper, is usually organized around ideas, not the sources themselves as an annotated bibliography would be organized. This means that you will not just simply list your sources and go into detail about each one of them, one at a time. No. As you read widely but selectively in your topic area, consider instead what themes or issues connect your sources together. Do they present one or different solutions? Is there an aspect of the field that is missing? How well do they present the material and do they portray it according to an appropriate theory? Do they reveal a trend in the field? A raging debate? Pick one of these themes to focus the organization of your review.

Convey it to your reader

A literature review may not have a traditional thesis statement (one that makes an argument), but you do need to tell readers what to expect. Try writing a simple statement that lets the reader know what is your main organizing principle. Here are a couple of examples:

The current trend in treatment for congestive heart failure combines surgery and medicine. More and more cultural studies scholars are accepting popular media as a subject worthy of academic consideration.

Consider organization

You’ve got a focus, and you’ve stated it clearly and directly. Now what is the most effective way of presenting the information? What are the most important topics, subtopics, etc., that your review needs to include? And in what order should you present them? Develop an organization for your review at both a global and local level:

First, cover the basic categories

Just like most academic papers, literature reviews also must contain at least three basic elements: an introduction or background information section; the body of the review containing the discussion of sources; and, finally, a conclusion and/or recommendations section to end the paper. The following provides a brief description of the content of each:

  • Introduction: Gives a quick idea of the topic of the literature review, such as the central theme or organizational pattern.
  • Body: Contains your discussion of sources and is organized either chronologically, thematically, or methodologically (see below for more information on each).
  • Conclusions/Recommendations: Discuss what you have drawn from reviewing literature so far. Where might the discussion proceed?

Organizing the body

Once you have the basic categories in place, then you must consider how you will present the sources themselves within the body of your paper. Create an organizational method to focus this section even further.

To help you come up with an overall organizational framework for your review, consider the following scenario:

You’ve decided to focus your literature review on materials dealing with sperm whales. This is because you’ve just finished reading Moby Dick, and you wonder if that whale’s portrayal is really real. You start with some articles about the physiology of sperm whales in biology journals written in the 1980’s. But these articles refer to some British biological studies performed on whales in the early 18th century. So you check those out. Then you look up a book written in 1968 with information on how sperm whales have been portrayed in other forms of art, such as in Alaskan poetry, in French painting, or on whale bone, as the whale hunters in the late 19th century used to do. This makes you wonder about American whaling methods during the time portrayed in Moby Dick, so you find some academic articles published in the last five years on how accurately Herman Melville portrayed the whaling scene in his novel.

Now consider some typical ways of organizing the sources into a review:

  • Chronological: If your review follows the chronological method, you could write about the materials above according to when they were published. For instance, first you would talk about the British biological studies of the 18th century, then about Moby Dick, published in 1851, then the book on sperm whales in other art (1968), and finally the biology articles (1980s) and the recent articles on American whaling of the 19th century. But there is relatively no continuity among subjects here. And notice that even though the sources on sperm whales in other art and on American whaling are written recently, they are about other subjects/objects that were created much earlier. Thus, the review loses its chronological focus.
  • By publication: Order your sources by publication chronology, then, only if the order demonstrates a more important trend. For instance, you could order a review of literature on biological studies of sperm whales if the progression revealed a change in dissection practices of the researchers who wrote and/or conducted the studies.
  • By trend: A better way to organize the above sources chronologically is to examine the sources under another trend, such as the history of whaling. Then your review would have subsections according to eras within this period. For instance, the review might examine whaling from pre-1600-1699, 1700-1799, and 1800-1899. Under this method, you would combine the recent studies on American whaling in the 19th century with Moby Dick itself in the 1800-1899 category, even though the authors wrote a century apart.
  • Thematic: Thematic reviews of literature are organized around a topic or issue, rather than the progression of time. However, progression of time may still be an important factor in a thematic review. For instance, the sperm whale review could focus on the development of the harpoon for whale hunting. While the study focuses on one topic, harpoon technology, it will still be organized chronologically. The only difference here between a “chronological” and a “thematic” approach is what is emphasized the most: the development of the harpoon or the harpoon technology.But more authentic thematic reviews tend to break away from chronological order. For instance, a thematic review of material on sperm whales might examine how they are portrayed as “evil” in cultural documents. The subsections might include how they are personified, how their proportions are exaggerated, and their behaviors misunderstood. A review organized in this manner would shift between time periods within each section according to the point made.
  • Methodological: A methodological approach differs from the two above in that the focusing factor usually does not have to do with the content of the material. Instead, it focuses on the “methods” of the researcher or writer. For the sperm whale project, one methodological approach would be to look at cultural differences between the portrayal of whales in American, British, and French art work. Or the review might focus on the economic impact of whaling on a community. A methodological scope will influence either the types of documents in the review or the way in which these documents are discussed. Once you’ve decided on the organizational method for the body of the review, the sections you need to include in the paper should be easy to figure out. They should arise out of your organizational strategy. In other words, a chronological review would have subsections for each vital time period. A thematic review would have subtopics based upon factors that relate to the theme or issue.

Sometimes, though, you might need to add additional sections that are necessary for your study, but do not fit in the organizational strategy of the body. What other sections you include in the body is up to you. Put in only what is necessary. Here are a few other sections you might want to consider:

  • Current Situation: Information necessary to understand the topic or focus of the literature review.
  • History: The chronological progression of the field, the literature, or an idea that is necessary to understand the literature review, if the body of the literature review is not already a chronology.
  • Methods and/or Standards: The criteria you used to select the sources in your literature review or the way in which you present your information. For instance, you might explain that your review includes only peer-reviewed articles and journals.

Questions for Further Research: What questions about the field has the review sparked? How will you further your research as a result of the review?

Begin composing

Once you’ve settled on a general pattern of organization, you’re ready to write each section. There are a few guidelines you should follow during the writing stage as well. Here is a sample paragraph from a literature review about sexism and language to illuminate the following discussion:

However, other studies have shown that even gender-neutral antecedents are more likely to produce masculine images than feminine ones (Gastil, 1990). Hamilton (1988) asked students to complete sentences that required them to fill in pronouns that agreed with gender-neutral antecedents such as “writer,” “pedestrian,” and “persons.” The students were asked to describe any image they had when writing the sentence. Hamilton found that people imagined 3.3 men to each woman in the masculine “generic” condition and 1.5 men per woman in the unbiased condition. Thus, while ambient sexism accounted for some of the masculine bias, sexist language amplified the effect. (Source: Erika Falk and Jordan Mills, “Why Sexist Language Affects Persuasion: The Role of Homophily, Intended Audience, and Offense,” Women and Language19:2).

Use evidence

In the example above, the writers refer to several other sources when making their point. A literature review in this sense is just like any other academic research paper. Your interpretation of the available sources must be backed up with evidence to show that what you are saying is valid.

Be selective

Select only the most important points in each source to highlight in the review. The type of information you choose to mention should relate directly to the review’s focus, whether it is thematic, methodological, or chronological.

Use quotes sparingly

Falk and Mills do not use any direct quotes. That is because the survey nature of the literature review does not allow for in-depth discussion or detailed quotes from the text. Some short quotes here and there are okay, though, if you want to emphasize a point, or if what the author said just cannot be rewritten in your own words. Notice that Falk and Mills do quote certain terms that were coined by the author, not common knowledge, or taken directly from the study. But if you find yourself wanting to put in more quotes, check with your instructor.

Summarize and synthesize

Remember to summarize and synthesize your sources within each paragraph as well as throughout the review. The authors here recapitulate important features of Hamilton’s study, but then synthesize it by rephrasing the study’s significance and relating it to their own work.

Keep your own voice

While the literature review presents others’ ideas, your voice (the writer’s) should remain front and center. Notice that Falk and Mills weave references to other sources into their own text, but they still maintain their own voice by starting and ending the paragraph with their own ideas and their own words. The sources support what Falk and Mills are saying.

Use caution when paraphrasing

When paraphrasing a source that is not your own, be sure to represent the author’s information or opinions accurately and in your own words. In the preceding example, Falk and Mills either directly refer in the text to the author of their source, such as Hamilton, or they provide ample notation in the text when the ideas they are mentioning are not their own, for example, Gastil’s. For more information, please see our handout on plagiarism .

Revise, revise, revise

Draft in hand? Now you’re ready to revise. Spending a lot of time revising is a wise idea, because your main objective is to present the material, not the argument. So check over your review again to make sure it follows the assignment and/or your outline. Then, just as you would for most other academic forms of writing, rewrite or rework the language of your review so that you’ve presented your information in the most concise manner possible. Be sure to use terminology familiar to your audience; get rid of unnecessary jargon or slang. Finally, double check that you’ve documented your sources and formatted the review appropriately for your discipline. For tips on the revising and editing process, see our handout on revising drafts .

Works consulted

We consulted these works while writing this handout. This is not a comprehensive list of resources on the handout’s topic, and we encourage you to do your own research to find additional publications. Please do not use this list as a model for the format of your own reference list, as it may not match the citation style you are using. For guidance on formatting citations, please see the UNC Libraries citation tutorial . We revise these tips periodically and welcome feedback.

Anson, Chris M., and Robert A. Schwegler. 2010. The Longman Handbook for Writers and Readers , 6th ed. New York: Longman.

Jones, Robert, Patrick Bizzaro, and Cynthia Selfe. 1997. The Harcourt Brace Guide to Writing in the Disciplines . New York: Harcourt Brace.

Lamb, Sandra E. 1998. How to Write It: A Complete Guide to Everything You’ll Ever Write . Berkeley: Ten Speed Press.

Rosen, Leonard J., and Laurence Behrens. 2003. The Allyn & Bacon Handbook , 5th ed. New York: Longman.

Troyka, Lynn Quittman, and Doug Hesse. 2016. Simon and Schuster Handbook for Writers , 11th ed. London: Pearson.

You may reproduce it for non-commercial use if you use the entire handout and attribute the source: The Writing Center, University of North Carolina at Chapel Hill

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do literature reviews have results

How To Structure Your Literature Review

3 options to help structure your chapter.

By: Amy Rommelspacher (PhD) | Reviewer: Dr Eunice Rautenbach | November 2020 (Updated May 2023)

Writing the literature review chapter can seem pretty daunting when you’re piecing together your dissertation or thesis. As  we’ve discussed before , a good literature review needs to achieve a few very important objectives – it should:

  • Demonstrate your knowledge of the research topic
  • Identify the gaps in the literature and show how your research links to these
  • Provide the foundation for your conceptual framework (if you have one)
  • Inform your own  methodology and research design

To achieve this, your literature review needs a well-thought-out structure . Get the structure of your literature review chapter wrong and you’ll struggle to achieve these objectives. Don’t worry though – in this post, we’ll look at how to structure your literature review for maximum impact (and marks!).

The function of the lit review

But wait – is this the right time?

Deciding on the structure of your literature review should come towards the end of the literature review process – after you have collected and digested the literature, but before you start writing the chapter. 

In other words, you need to first develop a rich understanding of the literature before you even attempt to map out a structure. There’s no use trying to develop a structure before you’ve fully wrapped your head around the existing research.

Equally importantly, you need to have a structure in place before you start writing , or your literature review will most likely end up a rambling, disjointed mess. 

Importantly, don’t feel that once you’ve defined a structure you can’t iterate on it. It’s perfectly natural to adjust as you engage in the writing process. As we’ve discussed before , writing is a way of developing your thinking, so it’s quite common for your thinking to change – and therefore, for your chapter structure to change – as you write. 

Need a helping hand?

do literature reviews have results

Like any other chapter in your thesis or dissertation, your literature review needs to have a clear, logical structure. At a minimum, it should have three essential components – an  introduction , a  body   and a  conclusion . 

Let’s take a closer look at each of these.

1: The Introduction Section

Just like any good introduction, the introduction section of your literature review should introduce the purpose and layout (organisation) of the chapter. In other words, your introduction needs to give the reader a taste of what’s to come, and how you’re going to lay that out. Essentially, you should provide the reader with a high-level roadmap of your chapter to give them a taste of the journey that lies ahead.

Here’s an example of the layout visualised in a literature review introduction:

Example of literature review outline structure

Your introduction should also outline your topic (including any tricky terminology or jargon) and provide an explanation of the scope of your literature review – in other words, what you  will   and  won’t   be covering (the delimitations ). This helps ringfence your review and achieve a clear focus . The clearer and narrower your focus, the deeper you can dive into the topic (which is typically where the magic lies). 

Depending on the nature of your project, you could also present your stance or point of view at this stage. In other words, after grappling with the literature you’ll have an opinion about what the trends and concerns are in the field as well as what’s lacking. The introduction section can then present these ideas so that it is clear to examiners that you’re aware of how your research connects with existing knowledge .

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2: The Body Section

The body of your literature review is the centre of your work. This is where you’ll present, analyse, evaluate and synthesise the existing research. In other words, this is where you’re going to earn (or lose) the most marks. Therefore, it’s important to carefully think about how you will organise your discussion to present it in a clear way. 

The body of your literature review should do just as the description of this chapter suggests. It should “review” the literature – in other words, identify, analyse, and synthesise it. So, when thinking about structuring your literature review, you need to think about which structural approach will provide the best “review” for your specific type of research and objectives (we’ll get to this shortly).

There are (broadly speaking)  three options  for organising your literature review.

The body section of your literature review is the where you'll present, analyse, evaluate and synthesise the existing research.

Option 1: Chronological (according to date)

Organising the literature chronologically is one of the simplest ways to structure your literature review. You start with what was published first and work your way through the literature until you reach the work published most recently. Pretty straightforward.

The benefit of this option is that it makes it easy to discuss the developments and debates in the field as they emerged over time. Organising your literature chronologically also allows you to highlight how specific articles or pieces of work might have changed the course of the field – in other words, which research has had the most impact . Therefore, this approach is very useful when your research is aimed at understanding how the topic has unfolded over time and is often used by scholars in the field of history. That said, this approach can be utilised by anyone that wants to explore change over time .

Adopting the chronological structure allows you to discuss the developments and debates in the field as they emerged over time.

For example , if a student of politics is investigating how the understanding of democracy has evolved over time, they could use the chronological approach to provide a narrative that demonstrates how this understanding has changed through the ages.

Here are some questions you can ask yourself to help you structure your literature review chronologically.

  • What is the earliest literature published relating to this topic?
  • How has the field changed over time? Why?
  • What are the most recent discoveries/theories?

In some ways, chronology plays a part whichever way you decide to structure your literature review, because you will always, to a certain extent, be analysing how the literature has developed. However, with the chronological approach, the emphasis is very firmly on how the discussion has evolved over time , as opposed to how all the literature links together (which we’ll discuss next ).

Option 2: Thematic (grouped by theme)

The thematic approach to structuring a literature review means organising your literature by theme or category – for example, by independent variables (i.e. factors that have an impact on a specific outcome).

As you’ve been collecting and synthesising literature , you’ll likely have started seeing some themes or patterns emerging. You can then use these themes or patterns as a structure for your body discussion. The thematic approach is the most common approach and is useful for structuring literature reviews in most fields.

For example, if you were researching which factors contributed towards people trusting an organisation, you might find themes such as consumers’ perceptions of an organisation’s competence, benevolence and integrity. Structuring your literature review thematically would mean structuring your literature review’s body section to discuss each of these themes, one section at a time.

The thematic structure allows you to organise your literature by theme or category  – e.g. by independent variables.

Here are some questions to ask yourself when structuring your literature review by themes:

  • Are there any patterns that have come to light in the literature?
  • What are the central themes and categories used by the researchers?
  • Do I have enough evidence of these themes?

PS – you can see an example of a thematically structured literature review in our literature review sample walkthrough video here.

Option 3: Methodological

The methodological option is a way of structuring your literature review by the research methodologies used . In other words, organising your discussion based on the angle from which each piece of research was approached – for example, qualitative , quantitative or mixed  methodologies.

Structuring your literature review by methodology can be useful if you are drawing research from a variety of disciplines and are critiquing different methodologies. The point of this approach is to question  how  existing research has been conducted, as opposed to  what  the conclusions and/or findings the research were.

The methodological structure allows you to organise your chapter by the analysis method  used - e.g. qual, quant or mixed.

For example, a sociologist might centre their research around critiquing specific fieldwork practices. Their literature review will then be a summary of the fieldwork methodologies used by different studies.

Here are some questions you can ask yourself when structuring your literature review according to methodology:

  • Which methodologies have been utilised in this field?
  • Which methodology is the most popular (and why)?
  • What are the strengths and weaknesses of the various methodologies?
  • How can the existing methodologies inform my own methodology?

3: The Conclusion Section

Once you’ve completed the body section of your literature review using one of the structural approaches we discussed above, you’ll need to “wrap up” your literature review and pull all the pieces together to set the direction for the rest of your dissertation or thesis.

The conclusion is where you’ll present the key findings of your literature review. In this section, you should emphasise the research that is especially important to your research questions and highlight the gaps that exist in the literature. Based on this, you need to make it clear what you will add to the literature – in other words, justify your own research by showing how it will help fill one or more of the gaps you just identified.

Last but not least, if it’s your intention to develop a conceptual framework for your dissertation or thesis, the conclusion section is a good place to present this.

In the conclusion section, you’ll need to present the key findings of your literature review and highlight the gaps that exist in the literature. Based on this, you'll  need to make it clear what your study will add  to the literature.

Example: Thematically Structured Review

In the video below, we unpack a literature review chapter so that you can see an example of a thematically structure review in practice.

Let’s Recap

In this article, we’ve  discussed how to structure your literature review for maximum impact. Here’s a quick recap of what  you need to keep in mind when deciding on your literature review structure:

  • Just like other chapters, your literature review needs a clear introduction , body and conclusion .
  • The introduction section should provide an overview of what you will discuss in your literature review.
  • The body section of your literature review can be organised by chronology , theme or methodology . The right structural approach depends on what you’re trying to achieve with your research.
  • The conclusion section should draw together the key findings of your literature review and link them to your research questions.

If you’re ready to get started, be sure to download our free literature review template to fast-track your chapter outline.

Literature Review Course

Psst… there’s more!

This post is an extract from our bestselling short course, Literature Review Bootcamp . If you want to work smart, you don't want to miss this .

28 Comments

Marin

Great work. This is exactly what I was looking for and helps a lot together with your previous post on literature review. One last thing is missing: a link to a great literature chapter of an journal article (maybe with comments of the different sections in this review chapter). Do you know any great literature review chapters?

ISHAYA JEREMIAH AYOCK

I agree with you Marin… A great piece

Qaiser

I agree with Marin. This would be quite helpful if you annotate a nicely structured literature from previously published research articles.

Maurice Kagwi

Awesome article for my research.

Ache Roland Ndifor

I thank you immensely for this wonderful guide

Malik Imtiaz Ahmad

It is indeed thought and supportive work for the futurist researcher and students

Franklin Zon

Very educative and good time to get guide. Thank you

Dozie

Great work, very insightful. Thank you.

KAWU ALHASSAN

Thanks for this wonderful presentation. My question is that do I put all the variables into a single conceptual framework or each hypothesis will have it own conceptual framework?

CYRUS ODUAH

Thank you very much, very helpful

Michael Sanya Oluyede

This is very educative and precise . Thank you very much for dropping this kind of write up .

Karla Buchanan

Pheeww, so damn helpful, thank you for this informative piece.

Enang Lazarus

I’m doing a research project topic ; stool analysis for parasitic worm (enteric) worm, how do I structure it, thanks.

Biswadeb Dasgupta

comprehensive explanation. Help us by pasting the URL of some good “literature review” for better understanding.

Vik

great piece. thanks for the awesome explanation. it is really worth sharing. I have a little question, if anyone can help me out, which of the options in the body of literature can be best fit if you are writing an architectural thesis that deals with design?

S Dlamini

I am doing a research on nanofluids how can l structure it?

PATRICK MACKARNESS

Beautifully clear.nThank you!

Lucid! Thankyou!

Abraham

Brilliant work, well understood, many thanks

Nour

I like how this was so clear with simple language 😊😊 thank you so much 😊 for these information 😊

Lindiey

Insightful. I was struggling to come up with a sensible literature review but this has been really helpful. Thank you!

NAGARAJU K

You have given thought-provoking information about the review of the literature.

Vakaloloma

Thank you. It has made my own research better and to impart your work to students I teach

Alphonse NSHIMIYIMANA

I learnt a lot from this teaching. It’s a great piece.

Resa

I am doing research on EFL teacher motivation for his/her job. How Can I structure it? Is there any detailed template, additional to this?

Gerald Gormanous

You are so cool! I do not think I’ve read through something like this before. So nice to find somebody with some genuine thoughts on this issue. Seriously.. thank you for starting this up. This site is one thing that is required on the internet, someone with a little originality!

kan

I’m asked to do conceptual, theoretical and empirical literature, and i just don’t know how to structure it

اخبار ورزشی امروز ایران اینترنشنال

Asking questions are actually fastidious thing if you are not understanding anything fully, but this article presents good understanding yet.

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Approaching literature review for academic purposes: The Literature Review Checklist

Debora f.b. leite.

I Departamento de Ginecologia e Obstetricia, Faculdade de Ciencias Medicas, Universidade Estadual de Campinas, Campinas, SP, BR

II Universidade Federal de Pernambuco, Pernambuco, PE, BR

III Hospital das Clinicas, Universidade Federal de Pernambuco, Pernambuco, PE, BR

Maria Auxiliadora Soares Padilha

Jose g. cecatti.

A sophisticated literature review (LR) can result in a robust dissertation/thesis by scrutinizing the main problem examined by the academic study; anticipating research hypotheses, methods and results; and maintaining the interest of the audience in how the dissertation/thesis will provide solutions for the current gaps in a particular field. Unfortunately, little guidance is available on elaborating LRs, and writing an LR chapter is not a linear process. An LR translates students’ abilities in information literacy, the language domain, and critical writing. Students in postgraduate programs should be systematically trained in these skills. Therefore, this paper discusses the purposes of LRs in dissertations and theses. Second, the paper considers five steps for developing a review: defining the main topic, searching the literature, analyzing the results, writing the review and reflecting on the writing. Ultimately, this study proposes a twelve-item LR checklist. By clearly stating the desired achievements, this checklist allows Masters and Ph.D. students to continuously assess their own progress in elaborating an LR. Institutions aiming to strengthen students’ necessary skills in critical academic writing should also use this tool.

INTRODUCTION

Writing the literature review (LR) is often viewed as a difficult task that can be a point of writer’s block and procrastination ( 1 ) in postgraduate life. Disagreements on the definitions or classifications of LRs ( 2 ) may confuse students about their purpose and scope, as well as how to perform an LR. Interestingly, at many universities, the LR is still an important element in any academic work, despite the more recent trend of producing scientific articles rather than classical theses.

The LR is not an isolated section of the thesis/dissertation or a copy of the background section of a research proposal. It identifies the state-of-the-art knowledge in a particular field, clarifies information that is already known, elucidates implications of the problem being analyzed, links theory and practice ( 3 - 5 ), highlights gaps in the current literature, and places the dissertation/thesis within the research agenda of that field. Additionally, by writing the LR, postgraduate students will comprehend the structure of the subject and elaborate on their cognitive connections ( 3 ) while analyzing and synthesizing data with increasing maturity.

At the same time, the LR transforms the student and hints at the contents of other chapters for the reader. First, the LR explains the research question; second, it supports the hypothesis, objectives, and methods of the research project; and finally, it facilitates a description of the student’s interpretation of the results and his/her conclusions. For scholars, the LR is an introductory chapter ( 6 ). If it is well written, it demonstrates the student’s understanding of and maturity in a particular topic. A sound and sophisticated LR can indicate a robust dissertation/thesis.

A consensus on the best method to elaborate a dissertation/thesis has not been achieved. The LR can be a distinct chapter or included in different sections; it can be part of the introduction chapter, part of each research topic, or part of each published paper ( 7 ). However, scholars view the LR as an integral part of the main body of an academic work because it is intrinsically connected to other sections ( Figure 1 ) and is frequently present. The structure of the LR depends on the conventions of a particular discipline, the rules of the department, and the student’s and supervisor’s areas of expertise, needs and interests.

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Interestingly, many postgraduate students choose to submit their LR to peer-reviewed journals. As LRs are critical evaluations of current knowledge, they are indeed publishable material, even in the form of narrative or systematic reviews. However, systematic reviews have specific patterns 1 ( 8 ) that may not entirely fit with the questions posed in the dissertation/thesis. Additionally, the scope of a systematic review may be too narrow, and the strict criteria for study inclusion may omit important information from the dissertation/thesis. Therefore, this essay discusses the definition of an LR is and methods to develop an LR in the context of an academic dissertation/thesis. Finally, we suggest a checklist to evaluate an LR.

WHAT IS A LITERATURE REVIEW IN A THESIS?

Conducting research and writing a dissertation/thesis translates rational thinking and enthusiasm ( 9 ). While a strong body of literature that instructs students on research methodology, data analysis and writing scientific papers exists, little guidance on performing LRs is available. The LR is a unique opportunity to assess and contrast various arguments and theories, not just summarize them. The research results should not be discussed within the LR, but the postgraduate student tends to write a comprehensive LR while reflecting on his or her own findings ( 10 ).

Many people believe that writing an LR is a lonely and linear process. Supervisors or the institutions assume that the Ph.D. student has mastered the relevant techniques and vocabulary associated with his/her subject and conducts a self-reflection about previously published findings. Indeed, while elaborating the LR, the student should aggregate diverse skills, which mainly rely on his/her own commitment to mastering them. Thus, less supervision should be required ( 11 ). However, the parameters described above might not currently be the case for many students ( 11 , 12 ), and the lack of formal and systematic training on writing LRs is an important concern ( 11 ).

An institutional environment devoted to active learning will provide students the opportunity to continuously reflect on LRs, which will form a dialogue between the postgraduate student and the current literature in a particular field ( 13 ). Postgraduate students will be interpreting studies by other researchers, and, according to Hart (1998) ( 3 ), the outcomes of the LR in a dissertation/thesis include the following:

  • To identify what research has been performed and what topics require further investigation in a particular field of knowledge;
  • To determine the context of the problem;
  • To recognize the main methodologies and techniques that have been used in the past;
  • To place the current research project within the historical, methodological and theoretical context of a particular field;
  • To identify significant aspects of the topic;
  • To elucidate the implications of the topic;
  • To offer an alternative perspective;
  • To discern how the studied subject is structured;
  • To improve the student’s subject vocabulary in a particular field; and
  • To characterize the links between theory and practice.

A sound LR translates the postgraduate student’s expertise in academic and scientific writing: it expresses his/her level of comfort with synthesizing ideas ( 11 ). The LR reveals how well the postgraduate student has proceeded in three domains: an effective literature search, the language domain, and critical writing.

Effective literature search

All students should be trained in gathering appropriate data for specific purposes, and information literacy skills are a cornerstone. These skills are defined as “an individual’s ability to know when they need information, to identify information that can help them address the issue or problem at hand, and to locate, evaluate, and use that information effectively” ( 14 ). Librarian support is of vital importance in coaching the appropriate use of Boolean logic (AND, OR, NOT) and other tools for highly efficient literature searches (e.g., quotation marks and truncation), as is the appropriate management of electronic databases.

Language domain

Academic writing must be concise and precise: unnecessary words distract the reader from the essential content ( 15 ). In this context, reading about issues distant from the research topic ( 16 ) may increase students’ general vocabulary and familiarity with grammar. Ultimately, reading diverse materials facilitates and encourages the writing process itself.

Critical writing

Critical judgment includes critical reading, thinking and writing. It supposes a student’s analytical reflection about what he/she has read. The student should delineate the basic elements of the topic, characterize the most relevant claims, identify relationships, and finally contrast those relationships ( 17 ). Each scientific document highlights the perspective of the author, and students will become more confident in judging the supporting evidence and underlying premises of a study and constructing their own counterargument as they read more articles. A paucity of integration or contradictory perspectives indicates lower levels of cognitive complexity ( 12 ).

Thus, while elaborating an LR, the postgraduate student should achieve the highest category of Bloom’s cognitive skills: evaluation ( 12 ). The writer should not only summarize data and understand each topic but also be able to make judgments based on objective criteria, compare resources and findings, identify discrepancies due to methodology, and construct his/her own argument ( 12 ). As a result, the student will be sufficiently confident to show his/her own voice .

Writing a consistent LR is an intense and complex activity that reveals the training and long-lasting academic skills of a writer. It is not a lonely or linear process. However, students are unlikely to be prepared to write an LR if they have not mastered the aforementioned domains ( 10 ). An institutional environment that supports student learning is crucial.

Different institutions employ distinct methods to promote students’ learning processes. First, many universities propose modules to develop behind the scenes activities that enhance self-reflection about general skills (e.g., the skills we have mastered and the skills we need to develop further), behaviors that should be incorporated (e.g., self-criticism about one’s own thoughts), and each student’s role in the advancement of his/her field. Lectures or workshops about LRs themselves are useful because they describe the purposes of the LR and how it fits into the whole picture of a student’s work. These activities may explain what type of discussion an LR must involve, the importance of defining the correct scope, the reasons to include a particular resource, and the main role of critical reading.

Some pedagogic services that promote a continuous improvement in study and academic skills are equally important. Examples include workshops about time management, the accomplishment of personal objectives, active learning, and foreign languages for nonnative speakers. Additionally, opportunities to converse with other students promotes an awareness of others’ experiences and difficulties. Ultimately, the supervisor’s role in providing feedback and setting deadlines is crucial in developing students’ abilities and in strengthening students’ writing quality ( 12 ).

HOW SHOULD A LITERATURE REVIEW BE DEVELOPED?

A consensus on the appropriate method for elaborating an LR is not available, but four main steps are generally accepted: defining the main topic, searching the literature, analyzing the results, and writing ( 6 ). We suggest a fifth step: reflecting on the information that has been written in previous publications ( Figure 2 ).

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First step: Defining the main topic

Planning an LR is directly linked to the research main question of the thesis and occurs in parallel to students’ training in the three domains discussed above. The planning stage helps organize ideas, delimit the scope of the LR ( 11 ), and avoid the wasting of time in the process. Planning includes the following steps:

  • Reflecting on the scope of the LR: postgraduate students will have assumptions about what material must be addressed and what information is not essential to an LR ( 13 , 18 ). Cooper’s Taxonomy of Literature Reviews 2 systematizes the writing process through six characteristics and nonmutually exclusive categories. The focus refers to the reviewer’s most important points of interest, while the goals concern what students want to achieve with the LR. The perspective assumes answers to the student’s own view of the LR and how he/she presents a particular issue. The coverage defines how comprehensive the student is in presenting the literature, and the organization determines the sequence of arguments. The audience is defined as the group for whom the LR is written.
  • Designating sections and subsections: Headings and subheadings should be specific, explanatory and have a coherent sequence throughout the text ( 4 ). They simulate an inverted pyramid, with an increasing level of reflection and depth of argument.
  • Identifying keywords: The relevant keywords for each LR section should be listed to guide the literature search. This list should mirror what Hart (1998) ( 3 ) advocates as subject vocabulary . The keywords will also be useful when the student is writing the LR since they guide the reader through the text.
  • Delineating the time interval and language of documents to be retrieved in the second step. The most recently published documents should be considered, but relevant texts published before a predefined cutoff year can be included if they are classic documents in that field. Extra care should be employed when translating documents.

Second step: Searching the literature

The ability to gather adequate information from the literature must be addressed in postgraduate programs. Librarian support is important, particularly for accessing difficult texts. This step comprises the following components:

  • Searching the literature itself: This process consists of defining which databases (electronic or dissertation/thesis repositories), official documents, and books will be searched and then actively conducting the search. Information literacy skills have a central role in this stage. While searching electronic databases, controlled vocabulary (e.g., Medical Subject Headings, or MeSH, for the PubMed database) or specific standardized syntax rules may need to be applied.

In addition, two other approaches are suggested. First, a review of the reference list of each document might be useful for identifying relevant publications to be included and important opinions to be assessed. This step is also relevant for referencing the original studies and leading authors in that field. Moreover, students can directly contact the experts on a particular topic to consult with them regarding their experience or use them as a source of additional unpublished documents.

Before submitting a dissertation/thesis, the electronic search strategy should be repeated. This process will ensure that the most recently published papers will be considered in the LR.

  • Selecting documents for inclusion: Generally, the most recent literature will be included in the form of published peer-reviewed papers. Assess books and unpublished material, such as conference abstracts, academic texts and government reports, are also important to assess since the gray literature also offers valuable information. However, since these materials are not peer-reviewed, we recommend that they are carefully added to the LR.

This task is an important exercise in time management. First, students should read the title and abstract to understand whether that document suits their purposes, addresses the research question, and helps develop the topic of interest. Then, they should scan the full text, determine how it is structured, group it with similar documents, and verify whether other arguments might be considered ( 5 ).

Third step: Analyzing the results

Critical reading and thinking skills are important in this step. This step consists of the following components:

  • Reading documents: The student may read various texts in depth according to LR sections and subsections ( defining the main topic ), which is not a passive activity ( 1 ). Some questions should be asked to practice critical analysis skills, as listed below. Is the research question evident and articulated with previous knowledge? What are the authors’ research goals and theoretical orientations, and how do they interact? Are the authors’ claims related to other scholars’ research? Do the authors consider different perspectives? Was the research project designed and conducted properly? Are the results and discussion plausible, and are they consistent with the research objectives and methodology? What are the strengths and limitations of this work? How do the authors support their findings? How does this work contribute to the current research topic? ( 1 , 19 )
  • Taking notes: Students who systematically take notes on each document are more readily able to establish similarities or differences with other documents and to highlight personal observations. This approach reinforces the student’s ideas about the next step and helps develop his/her own academic voice ( 1 , 13 ). Voice recognition software ( 16 ), mind maps ( 5 ), flowcharts, tables, spreadsheets, personal comments on the referenced texts, and note-taking apps are all available tools for managing these observations, and the student him/herself should use the tool that best improves his/her learning. Additionally, when a student is considering submitting an LR to a peer-reviewed journal, notes should be taken on the activities performed in all five steps to ensure that they are able to be replicated.

Fourth step: Writing

The recognition of when a student is able and ready to write after a sufficient period of reading and thinking is likely a difficult task. Some students can produce a review in a single long work session. However, as discussed above, writing is not a linear process, and students do not need to write LRs according to a specific sequence of sections. Writing an LR is a time-consuming task, and some scholars believe that a period of at least six months is sufficient ( 6 ). An LR, and academic writing in general, expresses the writer’s proper thoughts, conclusions about others’ work ( 6 , 10 , 13 , 16 ), and decisions about methods to progress in the chosen field of knowledge. Thus, each student is expected to present a different learning and writing trajectory.

In this step, writing methods should be considered; then, editing, citing and correct referencing should complete this stage, at least temporarily. Freewriting techniques may be a good starting point for brainstorming ideas and improving the understanding of the information that has been read ( 1 ). Students should consider the following parameters when creating an agenda for writing the LR: two-hour writing blocks (at minimum), with prespecified tasks that are possible to complete in one section; short (minutes) and long breaks (days or weeks) to allow sufficient time for mental rest and reflection; and short- and long-term goals to motivate the writing itself ( 20 ). With increasing experience, this scheme can vary widely, and it is not a straightforward rule. Importantly, each discipline has a different way of writing ( 1 ), and each department has its own preferred styles for citations and references.

Fifth step: Reflecting on the writing

In this step, the postgraduate student should ask him/herself the same questions as in the analyzing the results step, which can take more time than anticipated. Ambiguities, repeated ideas, and a lack of coherence may not be noted when the student is immersed in the writing task for long periods. The whole effort will likely be a work in progress, and continuous refinements in the written material will occur once the writing process has begun.

LITERATURE REVIEW CHECKLIST

In contrast to review papers, the LR of a dissertation/thesis should not be a standalone piece or work. Instead, it should present the student as a scholar and should maintain the interest of the audience in how that dissertation/thesis will provide solutions for the current gaps in a particular field.

A checklist for evaluating an LR is convenient for students’ continuous academic development and research transparency: it clearly states the desired achievements for the LR of a dissertation/thesis. Here, we present an LR checklist developed from an LR scoring rubric ( 11 ). For a critical analysis of an LR, we maintain the five categories but offer twelve criteria that are not scaled ( Figure 3 ). The criteria all have the same importance and are not mutually exclusive.

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First category: Coverage

1. justified criteria exist for the inclusion and exclusion of literature in the review.

This criterion builds on the main topic and areas covered by the LR ( 18 ). While experts may be confident in retrieving and selecting literature, postgraduate students must convince their audience about the adequacy of their search strategy and their reasons for intentionally selecting what material to cover ( 11 ). References from different fields of knowledge provide distinct perspective, but narrowing the scope of coverage may be important in areas with a large body of existing knowledge.

Second category: Synthesis

2. a critical examination of the state of the field exists.

A critical examination is an assessment of distinct aspects in the field ( 1 ) along with a constructive argument. It is not a negative critique but an expression of the student’s understanding of how other scholars have added to the topic ( 1 ), and the student should analyze and contextualize contradictory statements. A writer’s personal bias (beliefs or political involvement) have been shown to influence the structure and writing of a document; therefore, the cultural and paradigmatic background guide how the theories are revised and presented ( 13 ). However, an honest judgment is important when considering different perspectives.

3. The topic or problem is clearly placed in the context of the broader scholarly literature

The broader scholarly literature should be related to the chosen main topic for the LR ( how to develop the literature review section). The LR can cover the literature from one or more disciplines, depending on its scope, but it should always offer a new perspective. In addition, students should be careful in citing and referencing previous publications. As a rule, original studies and primary references should generally be included. Systematic and narrative reviews present summarized data, and it may be important to cite them, particularly for issues that should be understood but do not require a detailed description. Similarly, quotations highlight the exact statement from another publication. However, excessive referencing may disclose lower levels of analysis and synthesis by the student.

4. The LR is critically placed in the historical context of the field

Situating the LR in its historical context shows the level of comfort of the student in addressing a particular topic. Instead of only presenting statements and theories in a temporal approach, which occasionally follows a linear timeline, the LR should authentically characterize the student’s academic work in the state-of-art techniques in their particular field of knowledge. Thus, the LR should reinforce why the dissertation/thesis represents original work in the chosen research field.

5. Ambiguities in definitions are considered and resolved

Distinct theories on the same topic may exist in different disciplines, and one discipline may consider multiple concepts to explain one topic. These misunderstandings should be addressed and contemplated. The LR should not synthesize all theories or concepts at the same time. Although this approach might demonstrate in-depth reading on a particular topic, it can reveal a student’s inability to comprehend and synthesize his/her research problem.

6. Important variables and phenomena relevant to the topic are articulated

The LR is a unique opportunity to articulate ideas and arguments and to purpose new relationships between them ( 10 , 11 ). More importantly, a sound LR will outline to the audience how these important variables and phenomena will be addressed in the current academic work. Indeed, the LR should build a bidirectional link with the remaining sections and ground the connections between all of the sections ( Figure 1 ).

7. A synthesized new perspective on the literature has been established

The LR is a ‘creative inquiry’ ( 13 ) in which the student elaborates his/her own discourse, builds on previous knowledge in the field, and describes his/her own perspective while interpreting others’ work ( 13 , 17 ). Thus, students should articulate the current knowledge, not accept the results at face value ( 11 , 13 , 17 ), and improve their own cognitive abilities ( 12 ).

Third category: Methodology

8. the main methodologies and research techniques that have been used in the field are identified and their advantages and disadvantages are discussed.

The LR is expected to distinguish the research that has been completed from investigations that remain to be performed, address the benefits and limitations of the main methods applied to date, and consider the strategies for addressing the expected limitations described above. While placing his/her research within the methodological context of a particular topic, the LR will justify the methodology of the study and substantiate the student’s interpretations.

9. Ideas and theories in the field are related to research methodologies

The audience expects the writer to analyze and synthesize methodological approaches in the field. The findings should be explained according to the strengths and limitations of previous research methods, and students must avoid interpretations that are not supported by the analyzed literature. This criterion translates to the student’s comprehension of the applicability and types of answers provided by different research methodologies, even those using a quantitative or qualitative research approach.

Fourth category: Significance

10. the scholarly significance of the research problem is rationalized.

The LR is an introductory section of a dissertation/thesis and will present the postgraduate student as a scholar in a particular field ( 11 ). Therefore, the LR should discuss how the research problem is currently addressed in the discipline being investigated or in different disciplines, depending on the scope of the LR. The LR explains the academic paradigms in the topic of interest ( 13 ) and methods to advance the field from these starting points. However, an excess number of personal citations—whether referencing the student’s research or studies by his/her research team—may reflect a narrow literature search and a lack of comprehensive synthesis of ideas and arguments.

11. The practical significance of the research problem is rationalized

The practical significance indicates a student’s comprehensive understanding of research terminology (e.g., risk versus associated factor), methodology (e.g., efficacy versus effectiveness) and plausible interpretations in the context of the field. Notably, the academic argument about a topic may not always reflect the debate in real life terms. For example, using a quantitative approach in epidemiology, statistically significant differences between groups do not explain all of the factors involved in a particular problem ( 21 ). Therefore, excessive faith in p -values may reflect lower levels of critical evaluation of the context and implications of a research problem by the student.

Fifth category: Rhetoric

12. the lr was written with a coherent, clear structure that supported the review.

This category strictly relates to the language domain: the text should be coherent and presented in a logical sequence, regardless of which organizational ( 18 ) approach is chosen. The beginning of each section/subsection should state what themes will be addressed, paragraphs should be carefully linked to each other ( 10 ), and the first sentence of each paragraph should generally summarize the content. Additionally, the student’s statements are clear, sound, and linked to other scholars’ works, and precise and concise language that follows standardized writing conventions (e.g., in terms of active/passive voice and verb tenses) is used. Attention to grammar, such as orthography and punctuation, indicates prudence and supports a robust dissertation/thesis. Ultimately, all of these strategies provide fluency and consistency for the text.

Although the scoring rubric was initially proposed for postgraduate programs in education research, we are convinced that this checklist is a valuable tool for all academic areas. It enables the monitoring of students’ learning curves and a concentrated effort on any criteria that are not yet achieved. For institutions, the checklist is a guide to support supervisors’ feedback, improve students’ writing skills, and highlight the learning goals of each program. These criteria do not form a linear sequence, but ideally, all twelve achievements should be perceived in the LR.

CONCLUSIONS

A single correct method to classify, evaluate and guide the elaboration of an LR has not been established. In this essay, we have suggested directions for planning, structuring and critically evaluating an LR. The planning of the scope of an LR and approaches to complete it is a valuable effort, and the five steps represent a rational starting point. An institutional environment devoted to active learning will support students in continuously reflecting on LRs, which will form a dialogue between the writer and the current literature in a particular field ( 13 ).

The completion of an LR is a challenging and necessary process for understanding one’s own field of expertise. Knowledge is always transitory, but our responsibility as scholars is to provide a critical contribution to our field, allowing others to think through our work. Good researchers are grounded in sophisticated LRs, which reveal a writer’s training and long-lasting academic skills. We recommend using the LR checklist as a tool for strengthening the skills necessary for critical academic writing.

AUTHOR CONTRIBUTIONS

Leite DFB has initially conceived the idea and has written the first draft of this review. Padilha MAS and Cecatti JG have supervised data interpretation and critically reviewed the manuscript. All authors have read the draft and agreed with this submission. Authors are responsible for all aspects of this academic piece.

ACKNOWLEDGMENTS

We are grateful to all of the professors of the ‘Getting Started with Graduate Research and Generic Skills’ module at University College Cork, Cork, Ireland, for suggesting and supporting this article. Funding: DFBL has granted scholarship from Brazilian Federal Agency for Support and Evaluation of Graduate Education (CAPES) to take part of her Ph.D. studies in Ireland (process number 88881.134512/2016-01). There is no participation from sponsors on authors’ decision to write or to submit this manuscript.

No potential conflict of interest was reported.

1 The questions posed in systematic reviews usually follow the ‘PICOS’ acronym: Population, Intervention, Comparison, Outcomes, Study design.

2 In 1988, Cooper proposed a taxonomy that aims to facilitate students’ and institutions’ understanding of literature reviews. Six characteristics with specific categories are briefly described: Focus: research outcomes, research methodologies, theories, or practices and applications; Goals: integration (generalization, conflict resolution, and linguistic bridge-building), criticism, or identification of central issues; Perspective: neutral representation or espousal of a position; Coverage: exhaustive, exhaustive with selective citations, representative, central or pivotal; Organization: historical, conceptual, or methodological; and Audience: specialized scholars, general scholars, practitioners or policymakers, or the general public.

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How do I Write a Literature Review?: #5 Writing the Review

  • Step #1: Choosing a Topic
  • Step #2: Finding Information
  • Step #3: Evaluating Content
  • Step #4: Synthesizing Content
  • #5 Writing the Review
  • Citing Your Sources

WRITING THE REVIEW 

You've done the research and now you're ready to put your findings down on paper. When preparing to write your review, first consider how will you organize your review.

The actual review generally has 5 components:

Abstract  -  An abstract is a summary of your literature review. It is made up of the following parts:

  • A contextual sentence about your motivation behind your research topic
  • Your thesis statement
  • A descriptive statement about the types of literature used in the review
  • Summarize your findings
  • Conclusion(s) based upon your findings

Introduction :   Like a typical research paper introduction, provide the reader with a quick idea of the topic of the literature review:

  • Define or identify the general topic, issue, or area of concern. This provides the reader with context for reviewing the literature.
  • Identify related trends in what has already been published about the topic; or conflicts in theory, methodology, evidence, and conclusions; or gaps in research and scholarship; or a single problem or new perspective of immediate interest.
  • Establish your reason (point of view) for reviewing the literature; explain the criteria to be used in analyzing and comparing literature and the organization of the review (sequence); and, when necessary, state why certain literature is or is not included (scope)  - 

Body :  The body of a literature review contains your discussion of sources and can be organized in 3 ways-

  • Chronological -  by publication or by trend
  • Thematic -  organized around a topic or issue, rather than the progression of time
  • Methodical -  the focusing factor usually does not have to do with the content of the material. Instead, it focuses on the "methods" of the literature's researcher or writer that you are reviewing

You may also want to include a section on "questions for further research" and discuss what questions the review has sparked about the topic/field or offer suggestions for future studies/examinations that build on your current findings.

Conclusion :  In the conclusion, you should:

Conclude your paper by providing your reader with some perspective on the relationship between your literature review's specific topic and how it's related to it's parent discipline, scientific endeavor, or profession.

Bibliography :   Since a literature review is composed of pieces of research, it is very important that your correctly cite the literature you are reviewing, both in the reviews body as well as in a bibliography/works cited. To learn more about different citation styles, visit the " Citing Your Sources " tab.

  • Writing a Literature Review: Wesleyan University
  • Literature Review: Edith Cowan University
  • << Previous: Step #4: Synthesizing Content
  • Next: Citing Your Sources >>
  • Last Updated: Aug 22, 2023 1:35 PM
  • URL: https://libguides.eastern.edu/literature_reviews

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Speaker 1: A literature review is a summary of the existing research on a particular topic. It's typically done at the beginning of a research project and I did one for my undergraduate thesis, for my master's thesis and for my PhD thesis. And in this video I'm going to answer all of your literature review related questions. The first thing is how do you start a literature review? Well, to start a literature review, surprisingly or not surprisingly, you need literature. Where do you find that literature? Well, there's a ton of places. The first place I would go to is illicit.com. This is a new AI tool which allows you to ask a research question and get all of the papers related to that question. For example, here I can say how effective are conditional cash transfer programs? It will go away and search more than 125 million academic papers and here are the first four abstracts here. And here are all of the different researched peer-reviewed papers and that means that experts in the field have looked at these papers and said, yes, they are true. They are something that is a valuable contribution to the research field. So that's why you should be reading them. And we can go through and see that we've got a little summary and we just click through all of these and we can go and read them individually. That's one way, semantic searching. The next thing you can do is use Litmaps. Litmaps creates a map of literature for you to search. We can go in and create a map. Here I've created a map from one of my peer-reviewed papers that I wrote during my PhD and you can see I get a nice map of all of the other stuff that I need to read. You can do this with a single seed paper or you can put in a load of different papers in this tab in Discover to find out a load of different papers that you need to read about. Then you can also use something like Google Scholar. This is old school. This is like OG science and research. You'd go in, you just type keywords. For example, charge transport in OPV. So I'll click here and then here are all of the different papers that I should consider reading. Clearly, you don't need to read all of them but we'll get into that in a minute. But this is where you start. You start by searching the literature. You can have a look since 2024, since 2023 and this is the foundational activity for any literature review. Get comfortable searching the literature and you'll become a power user of all of the literature that you're about to write about. Before you start reading any literature, you need to have a literature review outline to work with. So this is the general structure of nearly every literature review for any field. It goes like this. First of all, we start with an introduction at the top. This introduction gives background information about the research field that you are investigating. It's in a reverse pyramid shape because this is the very, very broad step. This is where we're just sort of like looking at the overarching umbrella of our research field. Then optionally, we can talk about background and methods that are used to look for the research that we're going to talk about in the literature review. For example, you may want to say we looked at these databases, we looked at these sort of questions and background is the background of the field that you're specifically interested in. So we're going a little bit deeper, which is why it's the next step down on the inverse pyramid. Then we need all of the main text and this is all of the literature that you found searched by either theme. So you sort of group it together as like, this is a group of research that I can talk about because it's under one theme. Here's another theme or here's another theme and you've put research under that. So in here, you may have one, two, three plus themes under which you will talk about literature or, which is very uncommon I think these days, but you may be lucky that you may be able to sort this based on time, which means initially these people did this and then they did this and then they did this and that's how you structure your literature review. So you say they did this first, here's all the literature in the initial stages of that research, then they did this, here's the next stage of research, the evolution of that research field, here's the next stage. So it may be theme or time, it's completely up to you which one you use, but most people use theme. Once you've outlined all of the main themes and you've talked about the literature under that theme, then you need to have a discussion to bring it all together. This is where you're looking at all of the research themes and you're talking about your specific research question. Why are you doing this research into this literature and how does it help you sort of like answer the research question or the interest you have in a particular research field and why you're looking at the literature in the first place. And then you're looking at conclusions. Based on all of the stuff that you've read, all of the individual themes, all of the chronological studies, all of the papers you've included in this literature review, what conclusions can you make specifically about the current state of the field? And that is the general structure of nearly every literature review ever produced. Now, there's an easier way to do it obviously. What I like to do is go to ChatGPT and I just say, create a literature review outline for a study about and then whatever I'm interested in. Here I've got an example where it says, the effect of climate change on plants. And as you can see, it says introduction, background and here it says I want basic concepts of climate change. Then it says general impacts of climate change. Then we want direct effects of climate change on plants. So you can see we've started broad and we're getting narrower and narrower as the literature review goes on. And then we've got different themes. So we've got indirect effect of climate change on plants. So altered pests and disease dynamics, that's a theme. Changes in land use and habitat, that's a theme. And then we've got other themes underneath. So this is how you can easily structure and get a first kind of draft of the structure of any literature review that you're writing for nearly any subject. It's just amazing. And as you can see down here, the last one is conclusion, summary of key findings and then final thoughts on the importance of further research. So this is how we can use ChatGPT to structure our literature review outline. Nice stuff. Once you've got all of the literature you need to read and you've got a structure under which to put that literature, then you need to just write. You type out all of the stuff in your literature review. Before you do that, you may want to have a look at something like explainpaper.com that allows you to quickly understand peer-reviewed papers. Peer-reviewed papers are notoriously hard to read. They're dense, they're thick in academic language. And here, it's a really nice way to just get the simple summary. And I think this is one of the most powerful ones, explainpaper.com. All you need to do is highlight a certain area and over here, it will say, okay, explain your explanation. As a middle schooler, we can move this up and down and then we just click explain. And underneath, it will tell you the undergrad explanation of what you've just highlighted. A really great way, particularly if you're early on in your academic career, if you're undergraduate, if you're in high school, this is a great way to unlock all of the power that's behind the horrible language found in peer-reviewed academic papers. Once you understand what's actually in all of this, you've collected them into themes, you need to write it. There are a few tools that you can use. So you can use jenny.ai, that's an auto-writer for research papers and literature reviews. You can use yomoo.ai. And that is another sort of like auto-writer for peer-reviewed and papers. But to be honest with you, the best thing you can do is sit there with a Word document, with a Google document, Google, what do you even call that? Google Docs? Google Word? I completely forgot. Anyway, you know what I mean. You sit there with a word processor and you start typing. You put in your structured headlines and then you say under each one, what literature you're going to mention and you start fleshing it out. It takes ages and ages and many, many revisions. Make sure that you get someone you trust or your supervisor to look over it as you're writing it. Maybe each chapter or each theme that you write, you get someone to look over it and then at the end they look over everything all together. It's a really, really long process. It takes such a long time. For my thesis, it probably took a good few weeks to get all of the information into a sensible structure and literature review. So here we are, here's one of the themes. Overview of photocurrent generation in organic photovoltaic devices. So that's just one of many, many themes in this thesis and depending on what stage of study you're at, it could be long, it could be short but let's talk about that next. Okay, how long should a literature review be? Well, there are no hard and fast rules but I like to think about it like this. Is there enough in your literature review to provide enough context to what you're doing and what you're researching? Is there enough context for you to understand the problem that your literature review is looking at and addressing and also, is there enough data in there to talk about the up-to-date research and where the current state of the field is? That's really what we're looking at but here's some rules of thumb. So if you're doing it for an assignment, one thing I recommend that you look at is about 3,000 to 10,000 words. That's normally good enough to get an overview. For example, in my undergraduate thesis, it's only about seven pages. There's not much in there. There's some fancy diagrams, there's lots of references but ultimately, it's about seven pages. So it's not much. So 3,000 to 10,000 words is all you need for a small assignment or an undergraduate thesis whereas for master's and master's theses and PhD dissertations, one thing I recommend is you look at what's normal for your field. In some fields, it's like 10 pages. In other fields, it can be up to 40 pages but ultimately, as long as you have enough information and literature to be able to provide context to your problem and you provide an up-to-date representation of that research field, then you've got enough in there. Like I said, I like to use just the guide of what is normal for my research field before I start writing my thesis so I can say, okay, normally it's about 20 pages and therefore, I need to fill 20 pages worth of stuff and that is a good starting point for almost any literature review. So there we have it. That's the introduction to literature reviews. I'd love to know what you think and also, I have got so many videos on this very channel about literature reviews with AI, how to find literature using AI tools, how to write it in seconds using tools that are available online. I'll put all of the links below in the description so you can sort of build on the knowledge that we've gained in this video but if you really want to go look at a powerful video, go check out this one where I talk about how to write an exceptional literature review using AI. You won't be disappointed. Go check it out.

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do literature reviews have results

What is a Living Literature Review?

Table of contents.

The number of academic papers doubles every 12 years. This wealth of new knowledge is exciting, but the pace of growth makes keeping up with the latest developments increasingly difficult.

One response to this challenge is “living literature reviews”. At Open Phil, we define a living literature review as a continuously updated online collection of accessible articles that synthesize academic research on a specific topic. These reviews are primarily written by a single expert who is responsible for its quality and accuracy.

Living literature reviews aim to be accessible to readers unfamiliar with a field while maintaining rigor. Unlike news articles that often focus on single, sensational studies, these reviews provide a broader perspective, synthesizing findings from multiple sources. They differ from traditional academic literature reviews by avoiding paywalls, dense jargon, and lengthy formats that pose barriers to non-specialists. Moreover, because they don’t assume familiarity with the assumptions of a field, living literature reviews aim to describe how conclusions were reached, not just what the conclusions are. This transparency allows readers to better understand the research methodology and form their own judgment on the strength of the findings.

Living literature reviews also help readers assess a field by relying on a single individual to provide a consistent voice, perspective, and expert curatorial taste. While these individuals collaborate with other experts in their fields, having one consistent author allows readers to gauge how much they trust the author’s judgment over time.

Finally, living literature reviews leverage digital platforms for hosting and distribution. Websites allow for post-publication corrections and updates, enabling a level of currency that traditional print reviews can’t match. Complementing these, email newsletters and podcasts extend the reach and convenience of learning about academic research.

By making research accessible to a broader audience, living literature reviews can facilitate interdisciplinary connections and inform policy work. They offer insights into work happening in adjacent fields, potentially inspiring collaborations and novel research directions.

Open Philanthropy supports several living literature reviews:

  • New Things Under the Sun by Matt Clancy: social science research on science and innovation
  • Existential Crunch by Florian Jehn: academic literature on societal collapse
  • Some Are Useful by Tom Gebhart: how AI and machine learning are used in different parts of science
  • Good Questions Review by Paul Kellner: the relationship between academic research and policy impact

We are now seeking pre-proposals from individuals to write living literature reviews . We are particularly interested in reviews on neglected topics relevant to policymaking. Ideal candidates will have a PhD or equivalent expertise in their proposed area. Our support typically allows authors to dedicate a quarter to a third of their time to the project.

If you’re interested in launching your own living literature review, we encourage you to reach out. For more information on how to submit a pre-proposal, please contact [email protected] .

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Risk of incident venous thromboembolism in patients with atopic dermatitis: systematic analysis of the literature and meta-analysis

  • Published: 06 September 2024

Cite this article

do literature reviews have results

  • Yifei Wang 1 , 2   na1 ,
  • Zhiqiang Chen 3   na1 ,
  • Ting He 1 , 2 ,
  • Changzheng Huang 1 , 2 &
  • Chen Shen   ORCID: orcid.org/0000-0001-8231-9303 1 , 2  

Previous studies have showed conflicting results regarding the association between atopic dermatitis (AD) and venous thromboembolism (VTE) events.

Based on our systematic review of 6 cohort studies, patients with AD have an increased risk of VTE events.

These findings provide key evidence-based estimates to inform decision-making that VTE is a comorbidity of AD.

Atopic dermatitis (AD) is a prevalent chronic inflammatory skin disease. While various inflammatory conditions have been linked to venous thromboembolism (VTE), the risk of VTE among patients with AD remains unclear. We sought to systematically review and meta-analyze population-based studies to determine the association between AD and incident VTE. A systematic review was performed of published studies in PubMed, Web of Science, Embase and Cochrane library from their inception to 27 May 2024. At least two reviewers conducted title/abstract, full-text review and data extraction. Cohort studies examining the association of AD with incident VTE were included. Quality of evidence was assessed using the Newcastle-Ottawa Scale. Six cohort studies, encompassing a total of 10,186,861 participants, were included. The meta-analysis revealed a significantly increased risk for incident VTE among AD patients (pooled hazard ratio (HR), 1.10; 95% CI, 1.00–1.21), with an incidence rate of VTE at 3.35 events per 1000 patient-years. Individual outcome analyses suggested that AD was associated with higher risks of deep vein thrombosis (pooled HR, 1.15; 95% CI, 1.04–1.27) but not pulmonary embolism (pooled HR, 0.99; 95% CI, 0.87–1.13). This systematic review and meta-analysis indicated an increased risk of incident VTE among patients with AD. Future studies are necessary to elucidate the underlying pathophysiology of the association between AD and VTE.

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Risk of Venous Thromboembolism Among Patients with Atopic Dermatitis: A Cohort Study in a US Administrative Claims Database

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Controversial cardiovascular and hematologic comorbidities in atopic dermatitis, data availability.

The data of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

We thank Professor Adam J Adler for critically reading the manuscript.

This work was supported by the Fundamental Research Funds for the Central Universities, Grant/Award Numbers: YCJJ20230213.

Author information

Yifei Wang and Zhiqiang Chen contributed equally to this work.

Authors and Affiliations

Department of Dermatology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China

Yifei Wang, Ting He, Changzheng Huang & Chen Shen

Hubei Engineering Research Center for Skin Repair and Theranostics, Wuhan, 430022, China

Department of Vascular Surgery, Fuyang Hospital, Anhui Medical University, Fuyang, 236000, China

Zhiqiang Chen

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Contributions

Data curation: Yifei Wang, Zhiqiang Chen, Ting He, Changzheng Huang, Chen Shen. Methodology: Yifei Wang, Zhiqiang Chen, Ting He, Changzheng Huang, Chen Shen. Formal analysis and investigation: Yifei Wang, Zhiqiang Chen, Ting He, Changzheng Huang, Chen Shen. Writing – original draft preparation: Yifei Wang, Zhiqiang Chen, Chen Shen, Changzheng Huang. Writing – review and editing: Yifei Wang, Chen Shen, Changzheng Huang. Funding acquisition: Yifei Wang. All authors read and approved the final version of the manuscript.

Corresponding authors

Correspondence to Changzheng Huang or Chen Shen .

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Wang, Y., Chen, Z., He, T. et al. Risk of incident venous thromboembolism in patients with atopic dermatitis: systematic analysis of the literature and meta-analysis. J Thromb Thrombolysis (2024). https://doi.org/10.1007/s11239-024-03038-2

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Impacts of pfas exposure on neurodevelopment: a comprehensive literature review.

do literature reviews have results

1. Introduction

2. materials and methods, 2.1. data sourcing, 2.2. exposure assessment, 2.3. outcomes, 2.4. covariates, 2.5. data extraction, 3.1. the intelligence quotient (iq), 3.2. attention-deficit hyperactivity disorder (adhd), 3.3. autism spectrum disorder (asd), 4. discussion, 5. conclusions, author contributions, conflicts of interest.

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Click here to enlarge figure

First Author/Year/CountryDesignSample SizeAge of ChildrenPFASSample/
Measuring Method
Exposure MeasureTest Type and IndicatorAdjustment of CovariatesConclusion
Carly V Goodman/2023/Canada [ ]Cohort Studyn = 522Between 3 and 4PFOA, PFOS, and PFHxSPlasma/
UHPLC–MS/MS
PFOA: 1.68 (1.10–2.50), PFOS: 4.97 (3.20–6.20), PFHxS: 1.09 (0.67–1.60) (µg/L)Wechsler Preschool and Primary Scale of Intelligence, Third Edition (WPPSI-III), composite full-scale IQ (FSIQ), performance IQ (PIQ), and verbal IQ (VIQ) scoresGestational week of blood sampling, maternal age, pre-pregnancy BMI, country of birth (Canadian born, foreign born), maternal level of education (trade school diploma or lower, bachelor’s degree or higher), parity (0, 1, 2+), maternal smoking during pregnancy (current smoker, former smoker, never smoked), study site, and the Home Observation Measurement of the Environment (HOME) score, a continuous measure of the quality of the child’s home environmentEach doubling of PFHxS levels corresponded to a reduction of 2.0 points (95% CI: −3.6, −0.5) in FSIQ and 2.9 points (95% CI: −4.7, −1.1) in PIQ in males. However, in females, PFHxS showed no association with FSIQ or PIQ. PFOA and PFOS were also linked to lower PIQ scores in males (PFOA: B = −2.8, 95% CI: −4.9, −0.7; PFOS: B = −2.6, 95% CI: −4.8, −0.5), while in females, they were slightly positively associated with PIQ, but not FSIQ
Iben Have Beck/2023/Denmark [ ]Cohort Studyn = 9677 years oldPFOS, PFOA, PFHxS, PFNA, and PFDASerum/
LC–MS
PFOS: 4.61 (3.08–7.08), PFOA: 2.48 (1.58–3.49), PFHxS: 0.33 (0.21–0.50), PFNA: 0.57 (0.40–0.78), PFDA: 0.18 (0.13–0.24) (ng/mL)Abbreviated version of the Danish WISC-V, Full-Scale Intelligence Quotient (FSIQ) score, and Verbal Comprehension Index (VCI) scoreMaternal educational level, BMI, and sexPFOS and PFNA exposure and FSIQ remained significant, with β coefficients of −1.7 (95% CI: −3.0, −0.3) and −1.7 (95% CI: −3.0, −0.4)
Ann M Vuong/2019/United States [ ]Cohort Studyn = 2213 and 8 years oldPFOA, PFOS, PFHxS, and PFNASerum/
HPLC–MS/MS
PFOA: 2.4, PFOA: 3.9, PFHxS: 1.4, PFNA: 0.8 (ng/mL)Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV) and Full Scale IQ (FSIQ)Maternal sociodemographic, behavioral factors, and biological measurements of environmental chemicalFindings do not support that PFAS are adversely associated with cognitive function
Hui Wang/2023/China [ ]Cohort Studyn = 20314 years oldPFOA, PFOS, PFNA, PFUA, PFDA, PFHxS, PFBS, PFDoA, PFHpA, and PFOSAPlasma/
HPLC–MS/MS
PFOA: 13.12 (9.36–15.50), PFOS: 11.3 (6.66–13.68), PFNA: 2.05 (1.27–2.49), PFDA: 2.16 (1.18–2.67), PFHxS: 0.62 (0.42–0.69) (ng/mL)Wechsler Preschool and Primary Scales of Intelligence-Fourth Edition (WPPSI-IV)Maternal age at delivery, maternal educational level, maternal pre-pregnancy body mass index, parity, maternal folic acid intake during pregnancy, maternal place of birth, maternal active/passive smoking status during pregnancy, maternal freshwater fish intake during pregnancy, and self-reported economic statusNo significant associations between ln-transformed nine individual PFAS and child full scale IQ (FSIQ) or subscale IQ after adjusting for potential confounders
Zeyan Liew/2018/Norway [ ]Cohort Studyn = 15925 years oldPFOS, PFOA, PFHxS, PFNA, PFHpS, PFDA, and PFOSAPlasma/
LC–MS/MS
PFOS: 28.10 (21.60–35.80), PFOA: 4.28 (3.51–5.49), PFHxS: 1.07 (0.76–1.38), PFNA: 0.46 (0.36–0.57), PFHpS: 0.37 (0.27–0.49), PFDA: 0.17 (0.14–0.22), PFOSA: 2.32 (1.38–4.16) (ng/mL)Wechsler Primary and Preschool Scales of Intelligence–Revised (WPPSI-R)Maternal age at delivery, parity, maternal IQ, socioeconomic status, maternal smoking during pregnancy, maternal alcohol consumption during pregnancy, maternal prepregnancy BMI, child’s sexThere is no reliable evidence establishing a connection between prenatal exposure to PFAS and IQ scores in children at the age of five
Yan Wang/2015/United States [ ]Cohort Studyn = 1205 years oldPFHxS, PFOA, PFOS, PFNA, PFDeA, PFUnDA, PFDoDA, PFHpA, and PFHxASerum/
HPLC–MS/MS
PFHxS: 0.45 (0.35–0.57), PFOA: 2.00 (1.72–2.33), PFOS: 11.5 (10.2–13.07), PFNA: 1.33 (1.12–1.59), PFDeA: 0.39 (0.34–0.44), PFUnDA: 3.05 (2.37–3.94), PFDoDA: 0.29 (0.25–0.34) (ng/mL)Full-Scale Intelligence Quotient (FSIQ), verbal IQ (VIQ) and performance IQ (PIQ)Maternal age, maternal education, previous live births, family income, and maternal fish consumption during pregnancyExposure to two types of long-chain PFAS during pregnancy has been linked to lower IQ scores in children
Maria H Harris/2018/United States [ ]Cohort Studyn = 12263 years oldPFOA, PFOS, PFHxS, PFNA, MeFOSAA, and PFDeAPlasma/
HPLC–MS/MS
PFOA: 4.4 (3.1–6.0), PFOS: 6.2 (4.2–9.7), PFHxS: 1.9 (1.2–3.4), PFNA: 1.5 (1.1–2.3), MeFOSAA: 0.3 (<LOD −0.6), PFDeA: 0.3 (0.2–0.5) (ng/mL)Peabody Picture Vocabulary Test (PPVT-III), Wide Range Assessment of Visual Motor Abilities (WRAVMA), Kaufman Brief Intelligence Test (KBIT-2), and Visual Memory Index of the Wide Range Assessment of Memory and Learning (WRAML2)Child sex, age at cognitive testing, maternal race/ethnicity, age, maternal and paternal education, socioeconomic status and maternal intelligence scoresPrenatal PFAS were associated with both better and worse cognitive scores
Miranda J. Spratlen/2020/United States [ ]Cohort Studyn = 110Children ages 3–7 yearsPFOS, PFOA, PFHxS, PFNA, PFDS, PFBS, PFOSA, PFHxA, PFHpA, PFDA, PFUnDA, and PFDoDAPlasma/
HPLC–MS/MS
PFOS: 6.27 (1.05, 33.7), PFOA: 2.37 (0.18, 8.14), PFNA: 0.45 (<LOQ, 10.3), PFHxS: 0.69 (<LOQ, 15.8), PFDS: 0.13 (<LOQ, 0.64) (ng/mL)Bayley Scales of Infant Development (BSID-II), Mental Development Index (MDI), Psychomotor Development Index (PDI), and Wechsler Preschool and Primary Scale of Intelligence (WPPSI)Maternal age; material hardship during pregnancy; pre-pregnancy BMI; maternal IQ; maternal race; maternal education; home smoking exposure; marital status; parity; child’s gestational age at birth; exact child age on test date; child’s sex; maternal demoralization score; and child breastfeeding historyFindings on prenatal PFAS exposure and child neurodevelopment are inconsistent
Thea S. Skogheim/2020/Norway [ ]Longitudinal Prospective Studyn = 9443.5 years oldPFOA, PFNA, PFDA, PFUnDA, PFHxS, PFHpS, and PFOSPlasma/
LC–MS/MS
PFOA: 2.50 (1.77–3.21), PFNA: 0.41 (0.29–0.53), PFDA: 0.15 (0.10–0.23), PFUnDA: 0.22 (0.14–0.32), PFHxS: 0.65 (0.46–0.88), PFHpS: 0.15 (0.10–0.20), PFOS: 11.51 (8.77–14.84) (ng/mL)The Preschool Age Psychiatric Assessment interview, Child Development Inventory and Stanford–Binet (5th revision)Maternal age, maternal education, maternal fish intake, parity, maternal ADHD symptoms, child sex, premature birth, birth weight, maternal BMI, maternal smoking, maternal alcohol consumption, maternal anxiety/depression and maternal iodine intakeNo consistent evidence to conclude that prenatal exposure to PFAS are associated with cognitive dysfunctions in preschool children aged three and a half years
Boya Zhang/2024/China [ ]Cohort Studyn = 3277 years oldPFHpA, PFOA, PFNA, PFDA, PFUnDA, PFDoDA, PFBS, PFHxS, PFHpS, PFOS, PFDS, and PFOSASerum/
UHPLC–MS/MS
PFHpA: 0.27 (0.23–0.30), PFOA: 3.51 (3.29–3.75), PFNA: 0.32 (0.28–0.36), PFDA: 0.86 (0.76–0.96), PFUnDA: 0.61 (0.57–0.65), PFDoDA: 0.13 (0.12–0.14), PFBS: 0.08 (0.07–0.09), PFHxS: 0.09 (0.08–0.10), PFHpS: 0.06 (0.05–0.07), PFOS: 2.10 (1.98–2.22) (ng/mL)Wechsler Intelligence Scale for Children-Chinese Revised (WISC-CR)Maternal age at delivery, parity, maternal educational level, child’s sex, annual household income, pet ownership, changes in marital status, pre-pregnancy BMIIncreased prenatal exposure to PFAS negatively affected the IQ of school-aged children
First Author/Year/CountryDesignSample SizeAge of ChildrenPFASSample/Measuring MethodExposure MeasureTest Type and IndicatorAdjustment of CovariatesConclusion
Joan Forns/2020/Norway [ ]Cross-Sectional Studyn = 5183, 6, 12, and 24 months of agePFOS and PFOASerum/
HPLC–MS/MS
PFOS: 20.19 (4.1–87.3), PFOA: 1.83 (0.5–5.1) (ng/mL)Attention Syndrome Scale of the Child Behavior Checklist (CBCL-ADHD), Hyperactivity/Inattention Problems subscale of the Strengths and Difficulties Questionnaire (SDQ-Hyperactivity/Inattention), and ADHD Criteria of Diagnostic and Statistical Manual of Mental Disorders, 4th ed. (ADHD-DSM-IV)Maternal prepregnancy body mass index, maternal age at delivery, maternal education, maternal smoking during pregnancy, maternal parity, duration of total breastfeeding, and child sexExposure to PFOS or PFOA early in life was not linked to ADHD during childhood, with odds ratios (ORs) varying between 0.96 (95% CI: 0.87, 1.06) and 1.02 (95% CI: 0.93, 1.11). Analysis using stratified models indicates that the impact of PFAS may vary based on the child’s sex and the mother’s level of education
Louise Dalsager/2021/Denmark [ ]Cohort Studyn = 11382.5–5 years oldPFHxS, PFOS, PFOA, PFNA, and PFDASerum/
LC–MS/MS
PFOS: 4.65 (11.22), PFOA: 2.43 (6.40), PFHxS: 0.32 (0.81), PFNA: 0.58 (1.24), PFDA: 0.18 (0.37), Median (95th percentile) (ng/mL)Child Behavior Checklist 1.5–5Parity, maternal educational level, parental psychiatric diagnosis, child sexNo correlation has been found between PFAS levels in mothers or children and symptoms of ADHD
Johanna Inhyang Kim/2023/South Korea [ ]Prospective Cohort Studyn = 5212, 4, and 8 years oldPFOA, PFNA, PFDA, PFUnDA, PFHxS, and PFOSSerum/
HPLC–MS/MS
PFOA: 3.61 (1.91–6.72), PFNA: 0.99 (0.45–2.96), PFDA: 0.34 (0.12–0.94), PFUnDA: 0.45 (0.17–0.94), PFHxS: 1.01 (0.54–1.95), PFOS: 3.94 (1.80–7.47) (ng/mLADHD Rating Scale IV (ARS) Mother’s age during pregnancy, mother’s educational attainment, father’s educational background, socioeconomic conditions, maternal smoking during pregnancy, use of assisted reproductive technologies, maternal stress levels during pregnancyPFAS exposure at age 2 was associated with ADHD development at age 8
Ann M Vuong/2021/United States [ ]Cohort Studyn = 2405 and 8 years oldPFOA, PFHxS, PDNA, and PFOSSerum/
HPLC–MS/MS
PFOA: 5.3 (1.7), PFOS: 12.8 (1.7), PFHxS: 1.5 (0.8), PFNA: 0.90 (1.5), mean (SD) (ng/mL)The Behavioral Assessment System for Children-2 (BASC-2) and the Diagnostic Interview Schedule for Children–Young Child (DISC-YC) were used to evaluate ADHD symptoms and diagnostic criteriaMaternal age, race/ethnicity, education, family income, ln-maternal serum cotinine (ng/mL), maternal depression, marital status, maternal IQ, parity, and child sexPFOS and PFNA were consistently linked to hyperactive-impulsive ADHD traits across two validated assessment tools
Thea S. Skogheim/2021/Norway [ ]Cohort Studyn = 8213 years oldPFOA, PFNA, PFDA, PFUnDA, PFHxS, PFHpS, and PFOSPlasma/
LC–MS/MS
PFOA: 2.46 (3.46–2.86), PFNA: 0.42 (0.20–0.49), PFDA: 0.19 (0.15–0.23) (ng/mL)Adult ADHD Self-Report Scale (ASRS screener)Child sex, birth weight, and small for gestational age (SGA); maternal age at delivery, education, parity, pre-pregnancy body mass index (BMI, kg/m ), self-reported smoking and alcohol intake during pregnancy, as well as FFQ-based estimates of seafood (g/day), and dietary iodine intake (μg/day)Several PFAS (PFUnDA, PFDA, and PFOS) were inversely associated with odds of ADHD and/or ASD
Sachiko Itoh/2022/Japan [ ]Prospective Cohort Studyn = 7708 years oldPFHxS, PFOS, PFHxA, PFHpA, PFOA, PFNA, PFDA, PFUnDA, PFDoDA, PFTrDA, and PFTeDAPlasma/
UHPLC–MS/MS
PFHxS: 0.32 (0.22–0.41), PFOS: 6.66 (4.92–8.31), PFOA: 2.48 (1.50–3.00), PFNA: 1.16 (0.79–1.38), PFDA: 0.53 (0.34–0.62), PFUnDA: 1.37 (0.73–1.73), PFDoDA: 0.18 (0.12–0.23), PFTrDA: 0.35 (0.24–0.44) (ng/mL)ADHD Rating Scale (ADHD-RS)Age of the mother at delivery, number of previous pregnancies, level of education, body mass index before pregnancy, alcohol consumption during pregnancy, smoking habits during pregnancy, and the sex of the childHigher the maternal PFAS levels, lower the risk of ADHD symptoms at 8 y of age
Ilona Quaak/2016/The Netherlands [ ]Cohort Studyn = 7618 monthsPFOA, PFOS, PFHxS, PFHpS, PFNA, PFDA, and PFUnDAPlasma/
LC–MS/MS
PFOA: 905.6 (437.1), PFOS: 1583.6 (648.3), PFHxS: 140.0 (69.2), PFHpS: 35.6 (21.3), PFNA: 140.0 (61.8), PFDA: 52.2 (20.9), PFUnDA: 32.05 (11.9), Mean (SD) (ng/L)Child Behavior Checklist 1.5–5 (CBCL)Family history, educational level, smoking, alcohol use and illicit drug use during pregnancyPrenatal exposure to PFAS showed no significant associations with ADHD scores
Thea S. Skogheim/2020/Norway [ ]Cohort Studyn = 9443.5 years oldPFHpS, PFOS, PFHxS, PFOA, PFDA, PFUnDA, and PFNAPlasma/
LC–MS/MS
PFOA: 2.61 (1.77–3.21), PFNA: 0.45 (0.29–0.53), PFDA: 0.19 (0.10–0.23), PFUnDA: 0.25 (0.05–0.32), PFHxS: 0.79 (0.46–0.88), PFHpS: 0.16 (0.10–0.20), PFOS: 12.32 (8.77–14.84), (ng/mL)The Preschool Age Psychiatric Assessment interview, Child Development Inventory and Stanford–Binet (5th revision)Maternal age, maternal education, maternal fish intake, parity, maternal ADHD symptoms, child sex, premature birth, birth weight, maternal BMI, maternal smoking, maternal alcohol consumption, maternal anxiety/depression and maternal iodine intakeConsistent evidence was not found to link prenatal PFAS exposure with ADHD symptoms or cognitive impairments in preschool children around three and a half years old
Zeyan Liew/2015/United States [ ]Cohort Studyn = 220Average 10.7 years oldPFOS, PFOA, PFHxS, PFHpS, PFNA, and PFDAPlasma/
LC–MS/MS
PFOS: 26.80 (19.20, 35.00), PFOA: 4.06 (3.08, 5.50), PFHxS: 0.84 (0.61, 1.15), PFHpS: 0.30 (0.20, 0.40), PFNA: 0.42 (0.34, 0.52), PFDA: 0.15 (0.11, 0.20), (ng/mL)ICD-10 codes F90.0Maternal age at delivery, socioeconomic status, maternal smoking, alcohol drinking during pregnancy, mother’s self-reported psychiatric illnesses, child’s birth year, child’s sexEvidence does not consistently support a link between prenatal PFAS exposure and an increased risk of ADHD
First Author/Year/CountryDesignSample SizeAge of ChildrenPFASSample/Measuring MethodExposure MeasureTest Type and IndicatorAdjustment of CovariatesConclusion
Thea S. Skogheim/2021/Norway [ ]Cohort Studyn = 4003 years oldPFOA, PFNA, PFDA, PFUnDA, PFHxS, PFHpS, and PFOSPlasma/
LC–MS/MS
PFOA: 2.46 (3.46–2.86), PFNA: 0.42 (0.20–0.49), PFDA: 0.19 (0.15–0.23) (ng/mL)Diagnoses of “pervasive developmental disorders” were identified using ICD-10 codes F84.0, F84.1, F84.5, F84.8, or F84.9Child’s sex, birth weight, and status as small for gestational age (SGA); maternal age at delivery, education level, number of previous births, pre-pregnancy body mass index (BMI, kg/m ), self-reported smoking and alcohol consumption during pregnancy, as well as estimates of seafood intake (g/day) and dietary iodine intake (μg/day) based on a food frequency questionnaire (FFQ).An increased risk of Autism Spectrum Disorder (ASD) was observed in the second quartile of PFOA exposure [OR = 1.71 (95% CI: 1.20, 2.45)]. Conversely, PFUnDA, PFDA, and PFOS were associated with a reduced likelihood of ADHD, and the overall PFAS mixture showed a decreased risk of ASD [OR = 0.76 (95% CI: 0.64, 0.90)].
Jiwon Oh/2022/United States [ ]Case–control Studyn = 5512–5 years oldPFOS, PFHxS, PFNA, PFDA, PFPeA, PFUnDA, PFBS, PFHxA, MeFOSAA, and EtFOSAASerum/
HPLC–MS/MS
PFOA: 2.20 (0.91, 6.30), PFOS: 2.01 (0.81, 8.01), PFHxS: 0.59 (0.20, 3.05), PFNA: 0.71 (0.26, 2.49), PFDA: 0.14 (0.06, 0.49), PFPeA: 0.51 (0.20, 1.33), PFHpA: 0.23 (0.03, 1.00), PFUnDA: 0.03 (<LOD, 0.13), PFBS: <LOD (<LOD, 0.10), PFHxA: <LOD (<LOD, 0.43), MeFOSAA: 0.10 (<LOD, 1.56), EtFOSAA: <LOD (<LOD, 0.06) (ng/mL)Mullen Scales of Early Learning (MSEL) and Vineland Adaptive Behavior Scales (VABS) are combined to generate an Early Learning Composite (Composite) scoreChild’s sex, age at sampling, recruitment regional center; sampling year; gestational age at delivery, maternal factors, parity, breastfeeding duration, race/ethnicity, and socioeconomic status.PFOA was linked to higher odds of ASD, with an odds ratio (OR) of 1.99 per log ng/mL increase (95% CI: 1.20, 3.29). PFHpA also showed increased odds of ASD with an OR of 1.61 (95% CI: 1.21, 2.13). Conversely, perfluoroundecanoic acid (PFUnDA) was associated with lower odds of ASD, showing an OR of 0.43 (95% CI: 0.26, 0.69). Additionally, mixtures of PFAS were associated with increased odds of ASD, with an average OR of 1.57 and a range from the 5th to 95th percentile of 1.16 to 2.13.
Jiwon Oh/2021/United States [ ]Cohort Studyn = 573 years oldPFOA, PFOS, PFHxS, PFNA, PFDA, PFUnDA, PFDoDA, MeFOSAA, and EtFOSAASerum/
Reverse-Phase LC–MS/MS
PFOA: 0.9 (0.3–2.3), PFOS: 3.0 (1.1–6.8), PFHxS 0.4 (0.2–1.6), PFNA 0.5 (0.2–1.0), PFDA 0.1 (<LOD −0.4), PFUnDA 0.1 (<LOD −0.3), PFDoDA: <LOD (<LOD −0.1), MeFOSAA: 0.1 (<LOD −0.8), EtFOSAA <LOD (<LOD-<LOD) (ng/mL)Autism Diagnostic Observation Schedule (ADOS) and Mullen Scales of Early Learning (MSEL)Child’s sex, birth year, maternal vitamin intake in the first month of pregnancy, maternal education, and homeownership.PFOA and PFNA were positively associated with ASD risk, with relative risks (RR) of 1.20 (95% CI: 0.90, 1.61) and 1.24 (95% CI: 0.91, 1.69), respectively, for each 2-fold increase in concentration. In contrast, PFHxS was negatively associated with ASD risk, showing an RR of 0.88 (95% CI: 0.77, 1.01).
Jeong Weon Choi/2024/United States [ ]Cohort Studyn = 2803 years oldPFHxS, PFOS, PFOA, PFNA, and PFDASerum/
Reverse-Phase LC–MS/MS
PFHxS: 0.45 (0.2–1.60), PFOS: 2.93 (1.10–7.00), PFOA: 0.87 (0.35–2.10), PFNA: 0.48 (0.20–1.00), PFDA 0.14 (<LOD −0.40) (ng/mL)Autism Diagnostic Observation Schedule and Mullen Scales of Early Mullen Scales of Early LearningChild sex, child age at assessment, year of birth, gestational age at delivery, maternal age at delivery, parity, maternal pre-pregnancy BMI, maternal race/ethnicity, maternal education, breastfeeding duration, homeownership, maternal smoking status during pregnancy, and child ASD outcome group.PFOS, PFNA, and PFDA were associated with several behavioral problems among children diagnosed with ASD.
Hyeong-Moo Shin/2020/United States [ ]Case–control Studyn = 2392–5 years oldPFOA, PFOS, PFHxS, and PFNAPlasma/
Reverse-Phase HPLC–MS/MS
PFOA: 1.07 (0.37–3.40), PFOS: 3.10 (1.08–10.03), PFHxS: 0.50 (0.20–1.63), PFNA: 0.50 (<LOD −1.23) (ng/mL)Mullen Scales of Early Learning (MSEL), the Vineland Adaptive Behavior Scales (VABS), Autism Diagnostic Interview-Revised (ADI-R), Autism Diagnostic Observation Schedules-Generic (ADOS-G)Age and sex of the child at the time of assessment, year of birth, regional center of recruitment, number of previous pregnancies, gestational age at birth, maternal race/ethnicity, place of maternal birth, mother’s age at delivery, maternal BMI before pregnancy, vitamin intake around conception, duration of breastfeeding.Increases in PFHxS and PFOS levels were tentatively connected to a higher risk of ASD diagnosis in children. For each nanogram per milliliter increase, PFHxS had an odds ratio of 1.46 (95% CI: 0.98, 2.18) and PFOS had an odds ratio of 1.03 (95% CI: 0.99, 1.08).
Kristen Lyall/2018/United States [ ]Case–control Studen = 55315–19 weeks gestational ageEt-PFOSA, Me-PFOSA, PFDeA, PFHxS, PFNA, PFOA, PFOS, PFOSASerum/
Negative-ion Turbo Ion Spray–tandem mass spectrometry
Et-PFOSA: 0.68 (0.63, 0.73), Me-PFOSA: 1.14 (1.07, 1.23), PFDeA: 0.17 (0.16, 0.18), PFHxS: 1.39 (1.29, 1.49), PFNA: 0.60 (0.57, 0.63), PFOA: 3.58 (3.41, 3.76), PFOS: 17.5 (16.8, 18.3), PFOSA: 0.11 (0.10, 0.11) (ng/mL)Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV-TR) criteriaChild sex, month and year of birth, maternal age, country of maternal birth, maternal race/ethnicity, parity, and maternal education.While most PFAS prenatal concentrations were not significantly linked to ASD, notable inverse associations were observed for perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS). Specifically, the adjusted odds ratios for the highest versus lowest quartiles were 0.62 (95% CI: 0.41, 0.93) for PFOA and 0.64 (95% CI: 0.43, 0.97) for PFOS.
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Currie, S.D.; Wang, J.-S.; Tang, L. Impacts of PFAS Exposure on Neurodevelopment: A Comprehensive Literature Review. Environments 2024 , 11 , 188. https://doi.org/10.3390/environments11090188

Currie SD, Wang J-S, Tang L. Impacts of PFAS Exposure on Neurodevelopment: A Comprehensive Literature Review. Environments . 2024; 11(9):188. https://doi.org/10.3390/environments11090188

Currie, Seth D., Jia-Sheng Wang, and Lili Tang. 2024. "Impacts of PFAS Exposure on Neurodevelopment: A Comprehensive Literature Review" Environments 11, no. 9: 188. https://doi.org/10.3390/environments11090188

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Acupuncture: Effectiveness and Safety

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.header_greentext{color:green!important;font-size:24px!important;font-weight:500!important;}.header_bluetext{color:blue!important;font-size:18px!important;font-weight:500!important;}.header_redtext{color:red!important;font-size:28px!important;font-weight:500!important;}.header_darkred{color:#803d2f!important;font-size:28px!important;font-weight:500!important;}.header_purpletext{color:purple!important;font-size:31px!important;font-weight:500!important;}.header_yellowtext{color:yellow!important;font-size:20px!important;font-weight:500!important;}.header_blacktext{color:black!important;font-size:22px!important;font-weight:500!important;}.header_whitetext{color:white!important;font-size:22px!important;font-weight:500!important;}.header_darkred{color:#803d2f!important;}.Green_Header{color:green!important;font-size:24px!important;font-weight:500!important;}.Blue_Header{color:blue!important;font-size:18px!important;font-weight:500!important;}.Red_Header{color:red!important;font-size:28px!important;font-weight:500!important;}.Purple_Header{color:purple!important;font-size:31px!important;font-weight:500!important;}.Yellow_Header{color:yellow!important;font-size:20px!important;font-weight:500!important;}.Black_Header{color:black!important;font-size:22px!important;font-weight:500!important;}.White_Header{color:white!important;font-size:22px!important;font-weight:500!important;} What is acupuncture?

Acupuncture is a technique in which practitioners insert fine needles into the skin to treat health problems. The needles may be manipulated manually or stimulated with small electrical currents (electroacupuncture). Acupuncture has been in use in some form for at least 2,500 years. It originated from  traditional Chinese medicine but has gained popularity worldwide since the 1970s.

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According to the World Health Organization, acupuncture is used in 103 of 129 countries that reported data.

In the United States, data from the National Health Interview Survey show that the use of acupuncture by U.S. adults more than doubled between 2002 and 2022. In 2002, 1.0 percent of U.S. adults used acupuncture; in 2022, 2.2 percent used it. 

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National survey data indicate that in the United States, acupuncture is most commonly used for pain, such as back, joint, or neck pain.

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How acupuncture works is not fully understood. However, there’s evidence that acupuncture may have effects on the nervous system, effects on other body tissues, and nonspecific (placebo) effects. 

  • Studies in animals and people, including studies that used imaging methods to see what’s happening in the brain, have shown that acupuncture may affect nervous system function.
  • Acupuncture may have direct effects on the tissues where the needles are inserted. This type of effect has been seen in connective tissue.
  • Acupuncture has nonspecific effects (effects due to incidental aspects of a treatment rather than its main mechanism of action). Nonspecific effects may be due to the patient’s belief in the treatment, the relationship between the practitioner and the patient, or other factors not directly caused by the insertion of needles. In many studies, the benefit of acupuncture has been greater when it was compared with no treatment than when it was compared with sham (simulated or fake) acupuncture procedures, such as the use of a device that pokes the skin but does not penetrate it. These findings suggest that nonspecific effects contribute to the beneficial effect of acupuncture on pain or other symptoms. 
  • In recent research, a nonspecific effect was demonstrated in a unique way: Patients who had experienced pain relief during a previous acupuncture session were shown a video of that session and asked to imagine the treatment happening again. This video-guided imagery technique had a significant pain-relieving effect.

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Research has shown that acupuncture may be helpful for several pain conditions, including back or neck pain, knee pain associated with osteoarthritis, and postoperative pain. It may also help relieve joint pain associated with the use of aromatase inhibitors, which are drugs used in people with breast cancer. 

An analysis of data from 20 studies (6,376 participants) of people with painful conditions (back pain, osteoarthritis, neck pain, or headaches) showed that the beneficial effects of acupuncture continued for a year after the end of treatment for all conditions except neck pain.

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  • In a 2018 review, data from 12 studies (8,003 participants) showed acupuncture was more effective than no treatment for back or neck pain, and data from 10 studies (1,963 participants) showed acupuncture was more effective than sham acupuncture. The difference between acupuncture and no treatment was greater than the difference between acupuncture and sham acupuncture. The pain-relieving effect of acupuncture was comparable to that of nonsteroidal anti-inflammatory drugs (NSAIDs).
  • A 2017 clinical practice guideline from the American College of Physicians included acupuncture among the nondrug options recommended as first-line treatment for chronic low-back pain. Acupuncture is also one of the treatment options recommended for acute low-back pain. The evidence favoring acupuncture for acute low-back pain was judged to be of low quality, and the evidence for chronic low-back pain was judged to be of moderate quality.

For more information, see the  NCCIH webpage on low-back pain .

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  • In a 2018 review, data from 10 studies (2,413 participants) showed acupuncture was more effective than no treatment for osteoarthritis pain, and data from 9 studies (2,376 participants) showed acupuncture was more effective than sham acupuncture. The difference between acupuncture and no treatment was greater than the difference between acupuncture and sham acupuncture. Most of the participants in these studies had knee osteoarthritis, but some had hip osteoarthritis. The pain-relieving effect of acupuncture was comparable to that of NSAIDs.
  • A 2018 review evaluated 6 studies (413 participants) of acupuncture for hip osteoarthritis. Two of the studies compared acupuncture with sham acupuncture and found little or no difference between them in terms of effects on pain. The other four studies compared acupuncture with a variety of other treatments and could not easily be compared with one another. However, one of the trials indicated that the addition of acupuncture to routine care by a physician may improve pain and function in patients with hip osteoarthritis.
  • A 2019 clinical practice guideline from the American College of Rheumatology and the Arthritis Foundation conditionally recommends acupuncture for osteoarthritis of the knee, hip, or hand. The guideline states that the greatest number of studies showing benefits have been for knee osteoarthritis.

For more information, see the  NCCIH webpage on osteoarthritis .

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  • A 2020   review of nine studies that compared acupuncture with various drugs for preventing migraine found that acupuncture was slightly more effective, and study participants who received acupuncture were much less likely than those receiving drugs to drop out of studies because of side effects.
  • There’s moderate-quality evidence that acupuncture may reduce the frequency of migraines (from a 2016 evaluation of 22 studies with almost 5,000 people). The evidence from these studies also suggests that acupuncture may be better than sham acupuncture, but the difference is small. There is moderate- to low-quality evidence that acupuncture may reduce the frequency of tension headaches (from a 2016 evaluation of 12 studies with about 2,350 people).

For more information, see the  NCCIH webpage on headache .

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  • Myofascial pain syndrome is a common form of pain derived from muscles and their related connective tissue (fascia). It involves tender nodules called “trigger points.” Pressing on these nodules reproduces the patient’s pattern of pain.
  • A combined analysis of a small number of studies of acupuncture for myofascial pain syndrome showed that acupuncture applied to trigger points had a favorable effect on pain intensity (5 studies, 215 participants), but acupuncture applied to traditional acupuncture points did not (4 studies, 80 participants).  

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  • Sciatica involves pain, weakness, numbness, or tingling in the leg, usually on one side of the body, caused by damage to or pressure on the sciatic nerve—a nerve that starts in the lower back and runs down the back of each leg.
  • Two 2015 evaluations of the evidence, one including 12 studies with 1,842 total participants and the other including 11 studies with 962 total participants, concluded that acupuncture may be helpful for sciatica pain, but the quality of the research is not good enough to allow definite conclusions to be reached.

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  • A 2016 evaluation of 11 studies of pain after surgery (with a total of 682 participants) found that patients treated with acupuncture or related techniques 1 day after surgery had less pain and used less opioid pain medicine after the operation.

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  • A 2016 review of 20 studies (1,639 participants) indicated that acupuncture was not more effective in relieving cancer pain than conventional drug therapy. However, there was some evidence that acupuncture plus drug therapy might be better than drug therapy alone.
  • A 2017 review of 5 studies (181 participants) of acupuncture for aromatase inhibitor-induced joint pain in breast cancer patients concluded that 6 to 8 weeks of acupuncture treatment may help reduce the pain. However, the individual studies only included small numbers of women and used a variety of acupuncture techniques and measurement methods, so they were difficult to compare.
  • A larger 2018 study included 226 women with early-stage breast cancer who were taking aromatase inhibitors. The study found that the women who received 6 weeks of acupuncture treatment, given twice each week, reported less joint pain than the participants who received sham or no acupuncture.

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  • Chronic prostatitis/chronic pelvic pain syndrome is a condition in men that involves inflammation of or near the prostate gland; its cause is uncertain.
  • A review of 3 studies (204 total participants) suggested that acupuncture may reduce prostatitis symptoms, compared with a sham procedure. Because follow-up of the study participants was relatively brief and the numbers of studies and participants were small, a definite conclusion cannot be reached about acupuncture’s effects.

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  • A 2019 review of 41 studies (3,440 participants) showed that acupuncture was no more effective than sham acupuncture for symptoms of irritable bowel syndrome, but there was some evidence that acupuncture could be helpful when used in addition to other forms of treatment.

For more information, see the  NCCIH webpage on irritable bowel syndrome .

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  • A 2019 review of 12 studies (824 participants) of people with fibromyalgia indicated that acupuncture was significantly better than sham acupuncture for relieving pain, but the evidence was of low-to-moderate quality.

For more information, see the  NCCIH webpage on fibromyalgia . 

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In addition to pain conditions, acupuncture has also been studied for at least 50 other health problems. There is evidence that acupuncture may help relieve seasonal allergy symptoms, stress incontinence in women, and nausea and vomiting associated with cancer treatment. It may also help relieve symptoms and improve the quality of life in people with asthma, but it has not been shown to improve lung function.

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  • A 2015 evaluation of 13 studies of acupuncture for allergic rhinitis, involving a total of 2,365 participants, found evidence that acupuncture may help relieve nasal symptoms. The study participants who received acupuncture also had lower medication scores (meaning that they used less medication to treat their symptoms) and lower blood levels of immunoglobulin E (IgE), a type of antibody associated with allergies.
  • A 2014 clinical practice guideline from the American Academy of Otolaryngology–Head and Neck Surgery included acupuncture among the options health care providers may offer to patients with allergic rhinitis.

For more information, see the  NCCIH webpage on seasonal allergies .

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  • Stress incontinence is a bladder control problem in which movement—coughing, sneezing, laughing, or physical activity—puts pressure on the bladder and causes urine to leak.
  • In a 2017 study of about 500 women with stress incontinence, participants who received electroacupuncture treatment (18 sessions over 6 weeks) had reduced urine leakage, with about two-thirds of the women having a decrease in leakage of 50 percent or more. This was a rigorous study that met current standards for avoiding bias.

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  • Experts generally agree that acupuncture is helpful for treatment-related nausea and vomiting in cancer patients, but this conclusion is based primarily on research conducted before current guidelines for treating these symptoms were adopted. It’s uncertain whether acupuncture is beneficial when used in combination with current standard treatments for nausea and vomiting.

For more information, see the  NCCIH webpage on cancer .

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  • In a study conducted in Germany in 2017, 357 participants receiving routine asthma care were randomly assigned to receive or not receive acupuncture, and an additional 1,088 people who received acupuncture for asthma were also studied. Adding acupuncture to routine care was associated with better quality of life compared to routine care alone.
  • A review of 9 earlier studies (777 participants) showed that adding acupuncture to conventional asthma treatment improved symptoms but not lung function.

For more information, see the  NCCIH webpage on asthma .

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  • A 2018 review of 64 studies (7,104 participants) of acupuncture for depression indicated that acupuncture may result in a moderate reduction in the severity of depression when compared with treatment as usual or no treatment. However, these findings should be interpreted with caution because most of the studies were of low or very low quality.

For more information, see the  NCCIH webpage on depression .

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  • In recommendations on smoking cessation treatment issued in 2021, the U.S. Preventive Services Task Force, a panel of experts that makes evidence-based recommendations about disease prevention, did not make a recommendation about the use of acupuncture as a stop-smoking treatment because only limited evidence was available. This decision was based on a 2014 review of 9 studies (1,892 participants) that looked at the effect of acupuncture on smoking cessation results for 6 months or more and found no significant benefit. Some studies included in that review showed evidence of a possible small benefit of acupuncture on quitting smoking for shorter periods of time.

For more information, see the  NCCIH webpage on quitting smoking .

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  • A 2021 review evaluated 6 studies (2,507 participants) that compared the effects of acupuncture versus sham acupuncture on the success of in vitro fertilization as a treatment for infertility. No difference was found between the acupuncture and sham acupuncture groups in rates of pregnancy or live birth.
  • A 2020 review evaluated 12 studies (1,088 participants) on the use of acupuncture to improve sperm quality in men who had low sperm numbers and low sperm motility. The reviewers concluded that the evidence was inadequate for firm conclusions to be drawn because of the varied design of the studies and the poor quality of some of them. 

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  • A 2018 review of 12 studies with 869 participants concluded that acupuncture and laser acupuncture (a treatment that uses lasers instead of needles) may have little or no effect on carpal tunnel syndrome symptoms in comparison with sham acupuncture. It’s uncertain how the effects of acupuncture compare with those of other treatments for this condition.    
  • In a 2017 study not included in the review described above, 80 participants with carpal tunnel syndrome were randomly assigned to one of three interventions: (1) electroacupuncture to the more affected hand; (2) electroacupuncture at “distal” body sites, near the ankle opposite to the more affected hand; and (3) local sham electroacupuncture using nonpenetrating placebo needles. All three interventions reduced symptom severity, but local and distal acupuncture were better than sham acupuncture at producing desirable changes in the wrist and the brain.

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  • A 2018 review of studies of acupuncture for vasomotor symptoms associated with menopause (hot flashes and related symptoms such as night sweats) analyzed combined evidence from an earlier review of 15 studies (1,127 participants) and 4 newer studies (696 additional participants). The analysis showed that acupuncture was better than no acupuncture at reducing the frequency and severity of symptoms. However, acupuncture was not shown to be better than sham acupuncture.

For more information, see the  NCCIH webpage on menopause .

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  • Auricular acupuncture is a type of acupuncture that involves stimulating specific areas of the ear. 
  • In a 2019 review of 15 studies (930 participants) of auricular acupuncture or auricular acupressure (a form of auricular therapy that does not involve penetration with needles), the treatment significantly reduced pain intensity, and 80 percent of the individual studies showed favorable effects on various measures related to pain.
  • A 2020 review of 9 studies (783 participants) of auricular acupuncture for cancer pain showed that auricular acupuncture produced better pain relief than sham auricular acupuncture. Also, pain relief was better with a combination of auricular acupuncture and drug therapy than with drug therapy alone.
  • An inexpensive, easily learned form of auricular acupuncture called “battlefield acupuncture” has been used by the U.S. Department of Defense and Department of Veterans Affairs to treat pain. However, a 2021 review of 9 studies (692 participants) of battlefield acupuncture for pain in adults did not find any significant improvement in pain when this technique was compared with no treatment, usual care, delayed treatment, or sham battlefield acupuncture.

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  • Relatively few complications from using acupuncture have been reported. However, complications have resulted from use of nonsterile needles and improper delivery of treatments.
  • When not delivered properly, acupuncture can cause serious adverse effects, including infections, punctured organs, and injury to the central nervous system.
  • The U.S. Food and Drug Administration (FDA) regulates acupuncture needles as medical devices and requires that they be sterile and labeled for single use only.

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  • Some health insurance policies cover acupuncture, but others don’t. Coverage is often limited based on the condition being treated.
  • An analysis of data from the Medical Expenditure Panel Survey, a nationally representative U.S. survey, showed that the share of adult acupuncturist visits with any insurance coverage increased from 41.1 percent in 2010–2011 to 50.2 percent in 2018–2019.
  • Medicare covers acupuncture only for the treatment of chronic low-back pain. Coverage began in 2020. Up to 12 acupuncture visits are covered, with an additional 8 visits available if the first 12 result in improvement. Medicaid coverage of acupuncture varies from state to state.

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  • Most states license acupuncturists, but the requirements for licensing vary from state to state. To find out more about licensing of acupuncturists and other complementary health practitioners, visit the NCCIH webpage  Credentialing, Licensing, and Education . 

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NCCIH funds research to evaluate acupuncture’s effectiveness for various kinds of pain and other conditions and to further understand how the body responds to acupuncture and how acupuncture might work. Some recent NCCIH-supported studies involve:

  • Evaluating the feasibility of using acupuncture in hospital emergency departments.
  • Testing whether the effect of acupuncture on chronic low-back pain can be enhanced by combining it with transcranial direct current stimulation.
  • Evaluating a portable acupuncture-based nerve stimulation treatment for anxiety disorders.

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  • Don’t use acupuncture to postpone seeing a health care provider about a health problem.
  • Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

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Nccih clearinghouse.

The NCCIH Clearinghouse provides information on NCCIH and complementary and integrative health approaches, including publications and searches of Federal databases of scientific and medical literature. The Clearinghouse does not provide medical advice, treatment recommendations, or referrals to practitioners.

Toll-free in the U.S.: 1-888-644-6226

Telecommunications relay service (TRS): 7-1-1

Website: https://www.nccih.nih.gov

Email: [email protected] (link sends email)

Know the Science

NCCIH and the National Institutes of Health (NIH) provide tools to help you understand the basics and terminology of scientific research so you can make well-informed decisions about your health. Know the Science features a variety of materials, including interactive modules, quizzes, and videos, as well as links to informative content from Federal resources designed to help consumers make sense of health information.

Explaining How Research Works (NIH)

Know the Science: How To Make Sense of a Scientific Journal Article

Understanding Clinical Studies (NIH)

A service of the National Library of Medicine, PubMed® contains publication information and (in most cases) brief summaries of articles from scientific and medical journals. For guidance from NCCIH on using PubMed, see How To Find Information About Complementary Health Approaches on PubMed .

Website: https://pubmed.ncbi.nlm.nih.gov/

NIH Clinical Research Trials and You

The National Institutes of Health (NIH) has created a website, NIH Clinical Research Trials and You, to help people learn about clinical trials, why they matter, and how to participate. The site includes questions and answers about clinical trials, guidance on how to find clinical trials through ClinicalTrials.gov and other resources, and stories about the personal experiences of clinical trial participants. Clinical trials are necessary to find better ways to prevent, diagnose, and treat diseases.

Website: https://www.nih.gov/health-information/nih-clinical-research-trials-you

Research Portfolio Online Reporting Tools Expenditures & Results (RePORTER)

RePORTER is a database of information on federally funded scientific and medical research projects being conducted at research institutions.

Website: https://reporter.nih.gov

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  • Befus D, Coeytaux RR, Goldstein KM, et al.  Management of menopause symptoms with acupuncture: an umbrella systematic review and meta-analysis . Journal of Alternative and Complementary Medicine. 2018;24(4):314-323.
  • Bleck   R, Marquez E, Gold MA, et al.  A scoping review of acupuncture insurance coverage in the United States . Acupuncture in Medicine. 2020;964528420964214.
  • Briggs JP, Shurtleff D.  Acupuncture and the complex connections between the mind and the body. JAMA. 2017;317(24):2489-2490.
  • Brinkhaus B, Roll S, Jena S, et al.  Acupuncture in patients with allergic asthma: a randomized pragmatic trial. Journal of Alternative and Complementary Medicine. 2017;23(4):268-277.
  • Chan MWC, Wu XY, Wu JCY, et al.  Safety of acupuncture: overview of systematic reviews. Scientific Reports. 2017;7(1):3369.
  • Coyle ME, Stupans I, Abdel-Nour K, et al.  Acupuncture versus placebo acupuncture for in vitro fertilisation: a systematic review and meta-analysis. Acupuncture in Medicine. 2021;39(1):20-29.
  • Hershman DL, Unger JM, Greenlee H, et al.  Effect of acupuncture vs sham acupuncture or waitlist control on joint pain related to aromatase inhibitors among women with early-stage breast cancer: a randomized clinical trial. JAMA. 2018;320(2):167-176.
  • Linde K, Allais G, Brinkhaus B, et al.  Acupuncture for the prevention of episodic migraine. Cochrane Database of Systematic Reviews. 2016;(6):CD001218. Accessed at  cochranelibrary.com on February 12, 2021.
  • Linde K, Allais G, Brinkhaus B, et al.  Acupuncture for the prevention of tension-type headache. Cochrane Database of Systematic Reviews. 2016;(4):CD007587. Accessed at  cochranelibrary.com on February 12, 2021.
  • MacPherson H, Vertosick EA, Foster NE, et al. The persistence of the effects of acupuncture after a course of treatment: a meta-analysis of patients with chronic pain . Pain. 2017;158(5):784-793.
  • Qaseem A, Wilt TJ, McLean RM, et al.  Noninvasive treatments for acute, subacute, and chronic low back pain: a clinical practice guideline from the American College of Physicians. Annals of Internal Medicine. 2017;166(7):514-530.
  • Seidman MD, Gurgel RK, Lin SY, et al.  Clinical practice guideline: allergic rhinitis. Otolaryngology—Head and Neck Surgery. 2015;152(suppl 1):S1-S43.
  • Vickers AJ, Vertosick EA, Lewith G, et al. Acupuncture for chronic pain: update of an individual patient data meta-analysis . The Journal of Pain. 2018;19(5):455-474.
  • White AR, Rampes H, Liu JP, et al.  Acupuncture and related interventions for smoking cessation. Cochrane Database of Systematic Reviews. 2014;(1):CD000009. Accessed at  cochranelibrary.com on February 17, 2021.
  • Zia FZ, Olaku O, Bao T, et al.  The National Cancer Institute’s conference on acupuncture for symptom management in oncology: state of the science, evidence, and research gaps. Journal of the National Cancer Institute. Monographs. 2017;2017(52):lgx005.

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  • Adams D, Cheng F, Jou H, et al. The safety of pediatric acupuncture: a systematic review. Pediatrics. 2011;128(6):e1575-1587.
  • Candon M, Nielsen A, Dusek JA. Trends in insurance coverage for acupuncture, 2010-2019. JAMA Network Open. 2022;5(1):e2142509.
  • Cao J, Tu Y, Orr SP, et al. Analgesic effects evoked by real and imagined acupuncture: a neuroimaging study. Cerebral Cortex. 2019;29(8):3220-3231.
  • Centers for Medicare & Medicaid Services. Decision Memo for Acupuncture for Chronic Low Back Pain (CAG-00452N). Accessed at https://www.cms.gov/medicare-coverage-database/details/nca-decision-memo.aspx?NCAId=295 on June 25, 2021.
  • Chen L, Lin C-C, Huang T-W, et al. Effect of acupuncture on aromatase inhibitor-induced arthralgia in patients with breast cancer: a meta-analysis of randomized controlled trials . The Breast. 2017;33:132-138. 
  • Choi G-H, Wieland LS, Lee H, et al. Acupuncture and related interventions for the treatment of symptoms associated with carpal tunnel syndrome. Cochrane Database of Systematic Reviews. 2018;(12):CD011215. Accessed at cochranelibrary.com on January 28, 2021.
  • Cui J, Wang S, Ren J, et al. Use of acupuncture in the USA: changes over a decade (2002–2012). Acupuncture in Medicine. 2017;35(3):200-207.
  • Federman DG, Zeliadt SB, Thomas ER, et al. Battlefield acupuncture in the Veterans Health Administration: effectiveness in individual and group settings for pain and pain comorbidities. Medical Acupuncture. 2018;30(5):273-278.
  • Feng S, Han M, Fan Y, et al. Acupuncture for the treatment of allergic rhinitis: a systematic review and meta-analysis. American Journal of Rhinology & Allergy. 2015;29(1):57-62.
  • Franco JV, Turk T, Jung JH, et al. Non-pharmacological interventions for treating chronic prostatitis/chronic pelvic pain syndrome. Cochrane Database of Systematic Reviews. 2018;(5):CD012551. Accessed at cochranelibrary.com on January 28, 2021.
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Acknowledgments

NCCIH thanks Pete Murray, Ph.D., David Shurtleff, Ph.D., and Helene M. Langevin, M.D., NCCIH for their review of the 2022 update of this fact sheet. 

This publication is not copyrighted and is in the public domain. Duplication is encouraged.

NCCIH has provided this material for your information. It is not intended to substitute for the medical expertise and advice of your health care provider(s). We encourage you to discuss any decisions about treatment or care with your health care provider. The mention of any product, service, or therapy is not an endorsement by NCCIH.

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