benefits of a double blind experiment

16 Advantages and Disadvantages of a Double-Blind Study

A double-blind study uses a format where neither the participants nor the researchers know who receives a specific treatment. This procedure is useful because it prevents bias from forming in the achievable results. It is used most often when there is a direct need to understand the benefits of demand characteristics against the placebo effect.

What is unique about the placebo effect is that a person receives an inert substance that has no medical benefit. Participants believe that it is real medicine because a double-blind study wouldn’t inform anyone who gets the actual drug being studied. Researchers don’t receive that information either.

That means the results between the two groups can get compared to see if the effects of the drug are better than that of the placebo. It can also be a way to check for the development of side effects.

Several double-blind study advantages and disadvantages are worth reviewing when considering this format.

List of the Advantages of a Double-Blind Study

1. Three groups are typically part of a double-blind study. The typical double-blind study project will involve three groups of participants. You’ll have the treatment group, the placebo, group, and a control group. The first two receive the item in question based on their name, although only the administrator knows for certain who is getting what since researchers are kept in the dark. The control group doesn’t receive anything because it serves as the baseline against which the other two sets of results get compared.

When people in the placebo group improve more than the control group, then it shows a belief that the product works. If the treatment group shows better results than those who receive a placebo, then you know the medication worked.

2. It avoids deception in the research process. One of the criticized shortcomings of this approach is the fact that no one knows if the items they take or use is real or a placebo. The solution is to create two placebo subgroups where one is told that it is real medicine and the other is told it isn’t, which means researchers would need to deceive one set of participants. That process would violate the principles of informed consent.

The double-blind structure avoids this issue by providing complete information to all participants without letting on who receives the actual product getting studied.

3. It reduces the issue of experimenter bias. Using double-blind procedures can minimize the potential effects of research bias when collecting data. This issue often occurs when experimenters knowingly or unknowingly influence the results during information gathering or product administration during the project. There can also be subjective feelings that drive specific decisions that would occur if less information was present in the study.

By limiting the potential influences that could impact the collected data, the final results produced by the research or experiment has more validity.

4. The results of a double-blind project can get duplicated. One of the reasons why a double-blind study is considered a best practice is because the results offer the potential for duplication. Other researchers can follow the same protocols for administering placebos and the item being examined against a control group. If the results are similar, then it adds even more validity to the ability of a product or service to provide benefits. When duplication doesn’t happen, then the information from both studies can get compared to see what may have created a divergence in the data.

5. Double-blind assignment factors are randomized. No one knows who is going to be part of what group at the beginning of a double-blind study. The only participant group that knows they aren’t part of the placebo or target group are those who provide the control baselines. When looking at an intervention-based process, the fact that random assignment occurs for willing participants works to reduce the influence of confounding variables in the material.

6. High levels of control are part of the research process. The context of a double-blind research study allows administrators to manipulate variables so that the setting allows for direct observation. Control factors that could influence the environment can get added or removed to assist with the limitation of outside factors that would potentially change the data. This process allows for an accurate analysis of the collected data to ensure the authenticity of the results gets verified.

7. It is a process that’s usable in multiple industries. The double-blind study might be used primarily by the pharmaceutical industry because it can look directly at the impact of medication, but any field can use the processes to determine the validity of an idea. Agriculture, biology, chemistry, engineering, and social sciences all use these structures as a way to provide validation for a theory or idea.

List of the Disadvantages of a Double-Blind Study

1. It doesn’t reflect real-life circumstances. When a patient receives a pill after going to the doctor, they are told that the product is actual medicine intended to provide specific results. When participants receive something in a double-blind placebo study, then each person gets told explicitly that the item in question might be real medicine or a placebo. That leads to a different set of expectations that can influence the results of the work in adverse ways.

These artificial environments can cause an over-manipulation of the variables to produce circumstances that fall outside of the study’s parameters. When situations don’t feel realistic to a participant, then the quality of the data decreases exponentially.

2. Active placebos can interfere with the results. Double-blind studies respond to the objections of researchers unintentionally when communicating information about the results of a pill being authentic or a placebo. Objections to the pill offering this information don’t exist with this structure. Although both items look identical, the real medication provides biological effects. Even if the results aren’t measurable, the individuals can feel the impact of the medicine on their bodies.

This outcome may cause them to conclude that they are in the treatment group. That means some participants have a higher positive expectancy than those who don’t feel those effects. It is a disadvantage that can lead to a misinterpretation of the results being experienced in real-time.

3. It is not always possible to complete a double-blind study. There are times when a double-blind study is not possible. Any experiments that look at types of psychotherapy don’t benefit as an example because it would be impossible to keep participants in the dark about who receives treatment and who didn’t get the stated therapy. It only works when there is a way to provide two identical processes without clear communication about who receives the authentic item and who receives the placebo.

4. We do not fully understand the strength of the placebo effect. Research published by Science Translational Medicine in 2014 found that the simple act of taking a pill can establish a placebo effect for people. A migraine was being tested in this study. The control group took nothing, while the placebo group took a medication clearly labeled as “placebo.” Then one group took a migraine drug labeled with its name. Those who took the placebo had results that were 50% effective when reducing pain during a migraine effect.

The placebo effect can stimulate the brain into believing that the body is being healed, creating a natural mechanism that encourages better health. The presence of this effect doesn’t indicate the success or failure of a medication or another process in a double-blind study. It may be an indication that the group receiving the placebo has a powerful internal mechanism that provides self-healing.

5. Some people can have a negative response to a placebo. There can be times when an individual doesn’t have a response to the placebo at all. When that outcome occurs, then the effects of a process or medication can receive a direct comparison to see if the real product is useful. Some people can have an adverse reaction to the placebo, even producing unwanted side effects as if they were taking a real medication. It all depends on how each person feels.

A study involving people with asthma showed that using a placebo inhaler caused patients to do no better on breathing tests than sitting and doing nothing. When researchers asked how they felt about using the product, they reported that the placebo was just as effective as the regular medicine they used.

6. Randomization must use a structured process to be useful. The most common example of using randomization when assigning people to a group in a double-blind study is to flip a coin. It is an action that’s random and cannot be predicted, which means it is likely to be a 50/50 scenario over time as it gets tossed frequently. Assigning people who come to a specific location based on a day of the week can influence the results of the study unintentionally because there are other dynamics that control the behavior. That bias would be in the data without anyone recognizing its presence since it was placed there in the initial design.

7. Most double-blind studies are too small to provide a representative sample. Winchester Hospital, which is a division of Beth Israel Lahey Health in Massachusetts, says that a good double-blind study should enroll at least 100 individuals, “preferably as many as 300.” Effective treatments can prove themselves in small trials, but research requires more people to establish patterns so that results can be verified. Even when you have hundreds, or sometimes thousands, of participants in this work, the results might not extrapolate to the general population.

There were more than 4,100 trials in progress for pain treatments in 2011, but the only new approvals given were for formulations or updated dosages for existing medications. Even when drugs get into the third phase of testing, the product only has a 60% chance to continue moving forward. Divergent results often create failure.

8. It doesn’t work well for functional disorders. The highest response rates for a placebo occur when researchers are looking into functional disorders like Irritable Bowel Syndrome. It also happens when there are imprecise endpoint measurements, as with Crohn’s disease. People who have other immune-response conditions like rheumatoid arthritis. The FDA even notes that the placebo response is steadily growing in the general population.

This disadvantage creates another limitation where the structure of a double-blind study may not provide useful information.

9. Double-blind studies are an expensive effort to pursue. A double-blind study takes several months to complete so that researchers can look at each possible variable. It may be necessary to complete several efforts using different groups to collect enough data. When corporations look at the cost of these efforts, it can be an expense that reaches several million dollars before its completion. Government studies can quickly reach $1 billion or more, depending on the extent of the work and the industry or product under consideration.

When the Tufts Center for the Study of Drug Development looked at the cost of creating and bringing a new drug to the market, the expense was pegged at $2.6 billion. That’s why new prescription medicines are so expensive. Even the clinical trials for FDA approval have an average cost of $19 million.

Double-blind placebo studies are often called the gold standard for testing medications. This description is at its most powerful when studying new psychiatric medications since the placebo effect is a psychological benefit. It is a process that improves on the experiments that compare the response of someone taking a pill with those who do not.

Since no one knows who is getting what in a double-blind study, the danger of a researcher accidentally communicating non-verbally about the expectation of an item to work or not gets eliminated.

When reviewing these double-blind study advantages and disadvantages, the benefits that come from this process can only be achieved when structures that counter the potential negatives are in place. It gives us a baseline from which to work, but there are no guarantees that results are achievable.

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• Single, Double, & Triple Blind Study | Definition & Examples

Single, Double & Triple Blind Study | Definition & Examples

Published on July 10, 2020 by Lauren Thomas . Revised on June 22, 2023.

In experimental research, subjects are randomly assigned to either a treatment or control group. A double-blind study withholds each subject’s group assignment from both the participant and the researcher performing the experiment.

If participants know which group they are assigned to, there is a risk that they might change their behavior in a way that would influence the results. This can lead to a few types of research bias , particularly social desirability bias , self-selection bias , Hawthorne effect , or other demand characteristics .

Conversely, if researchers know which group a participant is assigned to, they might act in a way that reveals the assignment or directly influences the results. This can also lead to biases, particularly observer bias .

Double blinding guards against these risks, ensuring that any difference between the groups can be attributed to the treatment.

Table of contents

Different types of blinding, importance of blinding, other interesting articles, frequently asked questions about double-blind studies.

Blinding means withholding which group each participant has been assigned to. Studies may use single-, double- or triple-blinding.

Single-blinding occurs in many different kinds of studies, but double- and triple-blinding are mainly used in medical research.

Single blinding

If participants know whether they were assigned to the treatment or control group , they might modify their behavior as a result, potentially changing their eventual outcome.

In a single-blind experiment, participants do not know which group they have been placed in until after the experiment has finished.

If participants in the control group realize they have received a fake vaccine and are not protected against the flu, they might modify their behavior in ways that lower their chances of becoming sick – frequently washing their hands, avoiding crowded areas, etc. This behavior could narrow the gap in sickness rates between the control group and the treatment group, thus making the vaccine seem less effective than it really is.

Double-blinding

When the researchers administering the experimental treatment are aware of each participant’s group assignment, they may inadvertently treat those in the control group differently from those in the treatment group. This could reveal to participants their group assignment, or even directly influence the outcome itself.

In double-blind experiments, the group assignment is hidden from both the participant and the person administering the experiment.

If these experimenters knew which vaccines were real and which were fake, they might accidentally reveal this information to the participants, thus influencing their behavior and indirectly the results.

They could even directly influence the results. For instance, if experimenters expect the vaccine to result in lower levels of flu symptoms, they might accidentally measure symptoms incorrectly, thus making the vaccine appear more effective than it really is.

Triple-blinding

Although rarely implemented, triple-blind studies occur when group assignment is hidden not only from participants and administrators, but also from those tasked with analyzing the data after the experiment has concluded.

Researchers may expect a certain outcome and analyze the data in different ways until they arrive at the outcome they expected, even if it is merely a result of chance.

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Blinding helps ensure a study’s internal validity , or the extent to which you can be confident any link you find in your study is a true cause-and-effect relationship.

Since non-blinded studies can result in participants modifying their behavior or researchers finding effects that do not really exist, blinding is an important tool to avoid research bias in all types of scientific research.

Risk of unblinding

Unblinding occurs when researchers have blinded participants or experimenters, but they become aware of who received which treatment before the experiment has ended.

This may result in the same outcomes as would have occurred without any blinding.

You randomly assign some students to the new program (the treatment group), while others are instructed with a standard program (the control group). You use single blinding: you do not inform students whether they are receiving the new instruction program or the standard one.

If students become aware of which program they have been assigned to – for example, by talking to previous students about the content of the program – they may change their behavior. Students in the control group might work harder on their reading skills to make up for not receiving the new program, or conversely to put in less effort instead since they might believe the other students will do better than them anyway.

Inability to blind

Double or triple blinding is often not possible. While medical experiments can usually use a placebo or fake treatment for blinding, in other types of research, the treatment sometimes cannot be disguised from either the participant or the experimenter. For example, many treatments that physical therapists perform cannot be faked.

In such cases, you must rely on other methods to reduce bias.

• Running a single rather than double- or triple-blind study. Sometimes, although you might not be able to hide what each subject receives, you can still prevent them from knowing whether they are in the treatment or control group. Single blinding is particularly useful in non-medical studies where you cannot use a placebo in the control group.
• Relying on objective measures that participants and experimenters have less control over rather than subjective ones, like measuring fever rather than self-reported pain. This should reduce the possibility that participants or experimenters could influence the results.
• Pre-registering data analysis techniques. This will prevent researchers from trying different measures of analysis until they arrive at the answer they’re expecting.

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

• Student’s  t -distribution
• Normal distribution
• Null and Alternative Hypotheses
• Chi square tests
• Confidence interval
• Quartiles & Quantiles
• Cluster sampling
• Stratified sampling
• Data cleansing
• Reproducibility vs Replicability
• Peer review
• Prospective cohort study

Research bias

• Implicit bias
• Cognitive bias
• Placebo effect
• Hawthorne effect
• Hindsight bias
• Affect heuristic
• Social desirability bias

Blinding means hiding who is assigned to the treatment group and who is assigned to the control group in an experiment .

• In a single-blind study , only the participants are blinded.
• In a double-blind study , both participants and experimenters are blinded.
• In a triple-blind study , the assignment is hidden not only from participants and experimenters, but also from the researchers analyzing the data.

Blinding is important to reduce research bias (e.g., observer bias , demand characteristics ) and ensure a study’s internal validity .

If participants know whether they are in a control or treatment group , they may adjust their behavior in ways that affect the outcome that researchers are trying to measure. If the people administering the treatment are aware of group assignment, they may treat participants differently and thus directly or indirectly influence the final results.

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Double-Blind Experimental Study And Procedure Explained

Julia Simkus

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Julia Simkus is a graduate of Princeton University with a Bachelor of Arts in Psychology. She is currently studying for a Master's Degree in Counseling for Mental Health and Wellness in September 2023. Julia's research has been published in peer reviewed journals.

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On This Page:

What is a Blinded Study?

• Binding, or masking, refers to withholding information regarding treatment allocation from one or more participants in a clinical research study, typically in randomized control trials .
• A blinded study prevents the participants from knowing about their treatment to avoid bias in the research. Any information that can influence the subjects is withheld until the completion of the research.
• Blinding can be imposed on any participant in an experiment, including researchers, data collectors, evaluators, technicians, and data analysts. 
• Good blinding can eliminate experimental biases arising from the subjects’ expectations, observer bias, confirmation bias, researcher bias, observer’s effect on the participants, and other biases that may occur in a research test.
• Studies may use single-, double- or triple-blinding. A trial that is not blinded is called an open trial.

Double-Blind Studies

Double-blind studies are those in which neither the participants nor the experimenters know who is receiving a particular treatment.

Double blinding prevents bias in research results, specifically due to demand characteristics or the placebo effect.

Demand characteristics are subtle cues from researchers that can inform the participants of what the experimenter expects to find or how participants are expected to behave.

If participants know which group they are assigned to, they might change their behavior in a way that would influence the results. Similarly, if a researcher knows which group a participant is assigned to, they might act in a way that reveals the assignment or influences the results.

Double-blinding attempts to prevent these risks, ensuring that any difference(s) between the groups can be attributed to the treatment. 

On the other hand, single-blind studies are those in which the experimenters are aware of which participants are receiving the treatment while the participants are unaware.

Single-blind studies are beneficial because they reduce the risk of errors due to subject expectations. However, single-blind studies do not prevent observer bias, confirmation bias , or bias due to demand characteristics.

Because the experiments are aware of which participants are receiving which treatments, they are more likely to reveal subtle clues that can accidentally influence the research outcome.

Double-blind studies are considered the gold standard in research because they help to control for experimental biases arising from the subjects’ expectations and experimenter biases that emerge when the researchers unknowingly influence how the subjects respond or how the data is collected.

Using the double-blind method improves the credibility and validity of a study .

Example Double-Blind Studies

Rostock and Huber (2014) used a randomized, placebo-controlled, double-blind study to investigate the immunological effects of mistletoe extract. However, their study showed that double-blinding is impossible when the investigated therapy has obvious side effects. 

Using a double-blind study, Kobak et al. (2005) found that S t John’s wort ( Hypericum perforatum ) is not an efficacious treatment for anxiety disorder, specifically OCD.

Using the Yale–Brown Obsessive–Compulsive Scale (Y-BOCS), they found that the mean change with St John’s wort was not significantly different from the mean change found with placebo. 

Cakir et al. (2014) conducted a randomized, controlled, and double-blind study to test the efficacy of therapeutic ultrasound for managing knee osteoarthritis.

They found that all assessment parameters significantly improved in all groups without a significant difference, suggesting that therapeutic ultrasound provided no additional benefit in improving pain and functions in addition to exercise training.

Using a randomized double-blind study, Papachristofilou et al. (2021) found that whole-lung LDRT failed to improve clinical outcomes in critically ill patients admitted to the intensive care unit requiring mechanical ventilation for COVID-19 pneumonia.

Double-Blinding Procedure

Double blinding is typically used in clinical research studies or clinical trials to test the safety and efficacy of various biomedical and behavioral interventions.

In such studies, researchers tend to use a placebo. A placebo is an inactive substance, typically a sugar pill, that is designed to look like the drug or treatment being tested but has no effect on the individual taking it. 

The placebo pill was given to the participants who were randomly assigned to the control group. This group serves as a baseline to determine if exposure to the treatment had any significant effects.

Those randomly assigned to the experimental group are given the actual treatment in question. Data is collected from both groups and then compared to determine if the treatment had any impact on the dependent variable.

All participants in the study will take a pill or receive a treatment, but only some of them will receive the real treatment under investigation while the rest of the subjects will receive a placebo. 

With double blinding, neither the participants nor the experimenters will have any idea who receives the real drug and who receives the placebo. 

For Example

A common example of double-blinding is clinical studies that are conducted to test new drugs.

In these studies, researchers will use random assignment to allocate patients into one of three groups: the treatment/experimental group (which receives the drug), the placebo group (which receives an inactive substance that looks identical to the treatment but has no drug in it), and the control group (which receives no treatment).

Both participants and researchers are kept unaware of which participants are allocated to which of the three groups.

The effects of the drug are measured by recording any symptoms noticed in the patients.

Once the study is unblinded, and the researchers and participants are made aware of who is in which group, the data can be analyzed to determine whether the drug had effects that were not seen in the placebo or control group, but only in the experimental group. 

Double-blind studies can also be beneficial in nonmedical interventions, such as psychotherapIes.

Reduces risk of bias

Double-blinding can eliminate, or significantly reduce, both observer bias and participant biases.

Because both the researcher and the subjects are unaware of the treatment assignments, it is difficult for their expectations or behaviors to influence the study.

Results can be duplicated

The results of a double-blind study can be duplicated, enabling other researchers to follow the same processes, apply the same test item, and compare their results with the control group.

If the results are similar, then it adds more validity to the ability of a medication or treatment to provide benefits. 

It tests for three groups

Double-blind studies usually involve three groups of subjects: the treatment group, the placebo group, and the control group.

The treatment and placebo groups are both given the test item, although the researcher does not know which group is getting real treatment or placebo treatment.

The control group doesn’t receive anything because it serves as the baseline against which the other two groups are compared.

This is an advantage because if subjects in the placebo group improved more than the subjects in the control group, then researchers can conclude that the treatment administered worked.

Applicable across multiple industries

Double-blind studies can be used across multiple industries, such as agriculture, biology, chemistry, engineering, and social sciences.

Double-blind studies are used primarily by the pharmaceutical industry because researchers can look directly at the impact of medications. 

Disadvantages

Inability to blind.

In some types of research, specifically therapeutic, the treatment cannot always be disguised from the participant or the experimenter. In these cases, you must rely on other methods to reduce bias.

Additionally, imposing blinding may be impossible or unethical for some studies. 

Double-blinding can be expensive because the researcher has to examine all the possible variables and may have to use different groups to gather enough data. 

Small Sample Size

Most double-blind studies are too small to provide a representative sample. To be effective, it is generally recommended that double-blind trials include around 100-300 participants.

Studies involving fewer than 30 participants generally can’t provide proof of a theory. 

Negative Reaction to Placebo

In some instances, participants can have adverse reactions to the placebo, even producing unwanted side effects as if they were taking a real medication. 

It doesn’t reflect real-life circumstances

When participants receive treatment or medication in a double-blind placebo study, each individual is told that the item in question might be real medication or a placebo.

This artificial situation does not represent real-life circumstances because when a patient receives a pill after going to the doctor in the real-world, they are told that the product is actual medicine intended to benefit them.

When situations don’t feel realistic to a participant, then the quality of the data can decrease exponentially.

What is the difference between a single-blind, double-blind, and triple-blind study?

In a single-blind study, the experimenters are aware of which participants are receiving the treatment while the participants are unaware.

In a double-blind study, neither the patients nor the researchers know which study group the patients are in. In a triple-blind study, neither the patients, clinicians, nor the people carrying out the statistical analysis know which treatment the subjects had.

Is a double-blind study the same as a randomized clinical trial?

Yes, a double-blind study is a form of a randomized clinical trial in which neither the participants nor the researcher know if a subject is receiving the experimental treatment, a standard treatment, or a placebo.

Are double-blind studies ethical?

Double blinding is ethical only if it serves a scientific purpose. In most circumstances, it is unethical to conduct a double-blind placebo controlled trial where standard therapy exists.

What is the purpose of randomization using double blinding?

Randomization with blinding avoids reporting bias, since no one knows who is being treated and who is not, and thus all treatment groups should be treated the same. This reduces the influence of confounding variables and improves the reliability of clinical trial results.

Why are double-blind experiments considered the gold standard?

Randomized double-blind placebo control studies are considered the “gold standard” of epidemiologic studies as they provide the strongest possible evidence of causality.

Additionally, because neither the participants nor the researchers know who has received what treatment, double-blind studies minimize the placebo effect and significantly reduce bias.

Can blinding be used in qualitative studies?

Yes, blinding is used in qualitative studies .

Cakir, S., Hepguler, S., Ozturk, C., Korkmaz, M., Isleten, B., & Atamaz, F. C. (2014). Efficacy of therapeutic ultrasound for the management of knee osteoarthritis: a randomized, controlled, and double-blind study. American journal of physical medicine & rehabilitation , 93 (5), 405-412.

Kobak, K. A., Taylor, L. V., Bystritsky, A., Kohlenberg, C. J., Greist, J. H., Tucker, P., … & Vapnik, T. (2005). St John’s wort versus placebo in obsessive–compulsive disorder: results from a double-blind study. International Clinical Psychopharmacology , 20 (6), 299-304.

Papachristofilou, A., Finazzi, T., Blum, A., Zehnder, T., Zellweger, N., Lustenberger, J., … & Siegemund, M. (2021). Low-dose radiation therapy for severe COVID-19 pneumonia: a randomized double-blind study. International Journal of Radiation Oncology* Biology* Physics , 110 (5), 1274-1282. Rostock, M., & Huber, R. (2004). Randomized and double-blind studies–demands and reality as demonstrated by two examples of mistletoe research. Complementary Medicine Research , 11 (Suppl. 1), 18-22.

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Double-Blind Studies in Research

A double-blind study is one in which neither the participants nor the experimenters know who is receiving a particular treatment. This procedure is utilized to prevent bias in research results. Double-blind studies are particularly useful for preventing bias due to demand characteristics or the placebo effect .

For example, let's imagine that researchers are investigating the effects of a new drug. In a double-blind study, the researchers who interact with the participants would not know who was receiving the actual drug and who was receiving a placebo.

A Closer Look at Double-Blind Studies

Let’s take a closer look at what we mean by a double-blind study and how this type of procedure works. As mentioned previously, double-blind indicates that the participants and the experimenters are unaware of who is receiving the real treatment. What exactly do we mean by ‘treatment'? In a psychology experiment, the treatment is the level of the independent variable that the experimenters are manipulating.

This can be contrasted with a single-blind study in which the experimenters are aware of which participants are receiving the treatment while the participants remain unaware.

In such studies, researchers may use what is known as a placebo. A placebo is an inert substance, such as a sugar pill, that has no effect on the individual taking it. The placebo pill is given to participants who are randomly assigned to the control group. A control group is a subset of participants who are not exposed to any levels of the independent variable . This group serves as a baseline to determine if exposure to the independent variable had any significant effects.

Those randomly assigned to the experimental group are given the treatment in question. Data collected from both groups are then compared to determine if the treatment had some impact on the dependent variable .

All participants in the study will take a pill, but only some of them will receive the real drug under investigation. The rest of the subjects will receive an inactive placebo. With a double-blind study, the participants and the experimenters have no idea who is receiving the real drug and who is receiving the sugar pill.

Double-blind experiments are simply not possible in some scenarios. For example, in an experiment looking at which type of psychotherapy is the most effective, it would be impossible to keep participants in the dark about whether or not they actually received therapy.

Reasons to Use a Double-Blind Study

So why would researchers opt for such a procedure? There are a couple of important reasons.

• First, since the participants do not know which group they are in, their beliefs about the treatment are less likely to influence the outcome.
• Second, since researchers are unaware of which subjects are receiving the real treatment, they are less likely to accidentally reveal subtle clues that might influence the outcome of the research.  

The double-blind procedure helps minimize the possible effects of experimenter bias.   Such biases often involve the researchers unknowingly influencing the results during the administration or data collection stages of the experiment. Researchers sometimes have subjective feelings and biases that might have an influence on how the subjects respond or how the data is collected.

In one research article, randomized double-blind placebo studies were identified as the "gold standard" when it comes to intervention-based studies.   One of the reasons for this is the fact that random assignment reduces the influence of confounding variables.

Imagine that researchers want to determine if consuming energy bars before a demanding athletic event leads to an improvement in performance. The researchers might begin by forming a pool of participants that are fairly equivalent regarding athletic ability. Some participants are randomly assigned to a control group while others are randomly assigned to the experimental group.

Participants are then be asked to eat an energy bar. All of the bars are packaged the same, but some are sports bars while others are simply bar-shaped brownies. The real energy bars contain high levels of protein and vitamins, while the placebo bars do not.

Because this is a double-blind study, neither the participants nor the experimenters know who is consuming the real energy bars and who is consuming the placebo bars.

The participants then complete a predetermined athletic task, and researchers collect data performance. Once all the data has been obtained, researchers can then compare the results of each group and determine if the independent variable had any impact on the dependent variable.  

A Word From Verywell

A double-blind study can be a useful research tool in psychology and other scientific areas. By keeping both the experimenters and the participants blind, bias is less likely to influence the results of the experiment. 

A double-blind experiment can be set up when the lead experimenter sets up the study but then has a colleague (such as a graduate student) collect the data from participants. The type of study that researchers decide to use, however, may depend upon a variety of factors, including characteristics of the situation, the participants, and the nature of the hypothesis under examination.

National Institutes of Health. FAQs About Clinical Studies .

Misra S. Randomized double blind placebo control studies, the "Gold Standard" in intervention based studies . Indian J Sex Transm Dis AIDS . 2012;33(2):131-4. doi:10.4103/2589-0557.102130

Goodwin, CJ. Research In Psychology: Methods and Design . New York: John Wiley & Sons; 2010.

Kalat, JW. Introduction to Psychology . Boston, MA: Cengage Learning; 2017.

By Kendra Cherry, MSEd Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

Double-Blind Studies: The Secret to Reliable Research Results

Double-blind studies are essential to research in various fields, including health and psychology. In a double-blind study, neither the participants nor the researchers know who receives a particular treatment. This procedure prevents bias in research results, which demand characteristics or the placebo effect can cause.

By withholding information about the treatment, double-blind studies help ensure that the results are as accurate and unbiased as possible. This method is beneficial when testing the efficacy of new medications or treatments. Without a double-blind study, researchers may unintentionally influence the results by giving more attention or care to one group over another.

Double-blind studies are also beneficial for preventing the placebo effect when a participant experiences an improvement in symptoms simply because they believe they are receiving treatment. The placebo effect is minimized by keeping both the participants and researchers in the dark about who is receiving the treatment. Overall, double-blind studies are a crucial tool for producing trustworthy and reliable research results.

Importance of Double-Blind Studies

When conducting research, minimizing potential biases that may influence the results is essential. One way to achieve this is by using double-blind studies. Double-blind studies are a type of research where neither the participants nor the researchers know who is receiving a particular treatment. This procedure is utilized to prevent bias in research results.

By using a double-blind study, we can minimize the effects of demand characteristics or the placebo effect. Demand characteristics are the cues that participants pick from the researcher, which may influence their behavior. The placebo effect is the phenomenon where a participant’s belief in a treatment’s effectiveness improves their condition, even if the treatment is not practical.

Double-blind studies are instrumental in the field of medicine. They are commonly used to test the efficacy of new drugs. By using a double-blind study, we can ensure that the results are not biased towards the drug being tested. This is important because if the results were biased, it could lead to the approval of an ineffective or harmful drug.

In addition to medicine, double-blind studies are also used in psychology research. For example, in a study on the effects of a new therapy, a double-blind study can ensure that the participant’s beliefs about the therapy do not influence the results.

Double-Blind Studies in Clinical Trials

Clinical trials are an essential part of medical research. They help researchers determine whether a new treatment is safe and effective. Double-blind studies are often used in clinical trials to prevent bias and maximize the validity of the research results.

Designing a Clinical Trial

In a clinical trial, participants are randomly assigned to either a treatment or control group. In a double-blind study, neither the participants nor the researchers know who receives the treatment and the placebo. This helps prevent bias in the results.

To design a double-blind study, researchers must carefully consider the study’s objectives, the population being studied, and the treatment being tested. They must also ensure that the investigation is conducted ethically and that all participants are fully informed about the study’s risks and benefits.

Analyzing Results

Researchers analyze the results after a double-blind clinical trial to determine whether the treatment is effective. They compare the outcomes of the treatment group and the control group to see if there is a significant difference between the two. If the treatment is effective, researchers may seek approval from regulatory agencies to make the treatment available to the public.

Analyzing the results of a double-blind study requires careful statistical analysis. Researchers must ensure that the study’s sample size is large enough to detect meaningful differences between the treatment and control groups. They must also control for any variables affecting the results, such as age, gender, or underlying health conditions.

Double-Blind Studies in Social Sciences

In social sciences, double-blind studies are commonly used to investigate the effects of various interventions, such as psychotherapy, medication, or lifestyle changes. Double-blind studies are instrumental in social sciences research because they help eliminate bias and increase the validity of the findings.

Methodology

In a double-blind study, neither the participants nor the researchers know who receives the treatment and the placebo. This helps eliminate the placebo effect and other biases affecting the study results.

To conduct a double-blind study, researchers must first recruit participants and randomly assign them to either the treatment or the control group. Then, the researchers must administer the treatment and the placebo in an identical way in appearance, taste, and smell. This ensures that the participants cannot tell whether they receive the treatment or the placebo.

During the study, the researchers must also ensure that they know the treatment assignment to the participants. For example, they may use coded labels or have a third party administer the treatment.

Interpreting Findings

When interpreting the findings of a double-blind study, it is vital to consider the limitations of the study design. For example, double-blind studies may only be feasible in some situations, such as when the treatment involves a surgical procedure or has obvious side effects.

It is also essential to consider the sample size and the characteristics of the study population. Double-blind studies may not be generalizable to all people, and the findings may not apply to individuals with certain conditions or factors.

Despite these limitations, double-blind studies remain essential in social sciences research. They help increase the validity of the findings and provide valuable insights into the effectiveness of various interventions.

Challenges in Double-Blind Studies

Double-blind studies are an essential methodological feature of clinical research studies that help maximize the validity of the research results. However, there are several challenges associated with conducting double-blind studies. In this section, we will discuss some of the most significant challenges that researchers face when conducting double-blind studies.

Limitations

One of the primary challenges of double-blind studies is the limitations associated with blinding. Blinding is a process that involves withholding information regarding treatment allocation from one or more participants in a clinical research study. However, blinding is only sometimes possible or practical. For example, in some studies, it may be impossible to blind the participants or the researchers due to the nature of the intervention or the study design.

Another limitation of double-blind studies is the potential for unblinding. Unblinding occurs when a participant or a researcher becomes aware of the treatment allocation. Unblinding can occur accidentally or intentionally and compromise the study results’ validity.

Ethical Considerations

Double-blind studies also raise ethical considerations. For example, in some studies, blinding may not be ethical if the intervention poses a significant risk to the participants. In such cases, the participants must be informed of the treatment allocation to ensure their safety.

Additionally, blinding can create ethical dilemmas for researchers. For example, researchers may be hesitant to withhold or deceive participants’ information. Moreover, researchers must ensure that the participants understand the risks and benefits of participating in the study and provide informed consent.

Conducting double-blind studies comes with several challenges, including limitations and ethical considerations. As researchers, we must be aware of these challenges and take steps to address them to ensure the validity and ethicality of our studies.

Future of Double-Blind Studies

As we move towards a more technologically advanced future, how we conduct double-blind studies is also evolving. This section will discuss some technological advancements and emerging trends shaping the future of double-blind studies.

Technological Advancements

One of the most significant technological advancements impacting double-blind studies is wearable devices. These devices can track physiological parameters such as heart rate, blood pressure, and sleep patterns, providing researchers with a wealth of data. This data can be used to monitor the effects of a particular treatment and determine if it is effective.

Another technological advancement that is gaining popularity is the use of mobile apps. These apps can collect data from study participants, making it easier for researchers to monitor their progress. For example, an app could remind participants to take their medication at a specific time, ensuring they adhere to the study protocol.

Emerging Trends

One of the emerging trends in double-blind studies is the use of virtual reality (VR) . VR technology can be used to create realistic environments that simulate real-world scenarios. This can be particularly useful in studies that involve phobias or anxiety disorders. For example, a VR environment could simulate a fear of flying, allowing researchers to study the effects of a particular treatment in a controlled environment.

Another emerging trend is using artificial intelligence (AI) in double-blind studies. AI can analyze large amounts of data quickly and accurately, making it easier for researchers to identify patterns and trends. For example, AI could analyze data from wearable devices, identifying specific physiological parameters affected by a particular treatment.

Frequently Asked Questions

How do double-blind studies work.

Double-blind studies are a type of research study in which neither the participants nor the experimenters know which group each participant has been assigned to. This type of blinding helps to prevent bias in research results. In a double-blind study, each subject’s group assignment is withheld from both the participant and the researcher performing the experiment. The assignment is hidden not only from participants and experimenters, but also from the researchers analyzing the data.

What is the purpose of conducting double-blind studies?

The purpose of conducting double-blind studies is to prevent bias in research results. By withholding the group assignment from both the participant and the researcher performing the experiment, researchers can ensure that the results of the study are not influenced by any preconceived notions or expectations of the participants or the researchers.

What are the advantages of using double-blind studies in research?

The advantages of using double-blind studies in research are numerous. By preventing bias in research results, researchers can ensure that the results of the study are more accurate and reliable. This can help to improve the quality of research and the validity of the conclusions drawn from the research.

What are the limitations of double-blind studies?

While double-blind studies are an effective way to prevent bias in research results, they do have some limitations. For example, double-blind studies may be more difficult to conduct than other types of studies. Additionally, double-blind studies may be more expensive and time-consuming than other types of studies.

How are double-blind studies different from single-blind studies?

In a single-blind study, only the participants are blinded to the group assignment. In a double-blind study, both participants and experimenters are blinded. This type of blinding helps to prevent bias in research results. Single-blinding occurs in many different kinds of studies, but double- and triple-blinding are mainly used in medical research.

What are some examples of successful double-blind studies?

There have been many successful double-blind studies conducted in various fields of research. For example, a double-blind study conducted in the field of medicine found that a certain medication was more effective than a placebo in treating a particular condition. Another double-blind study conducted in the field of psychology found that a certain type of therapy was more effective than another type of therapy in treating a particular mental health condition.

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• Knowledge Base
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• What Is a Double-Blind Study? | Introduction & Examples

What Is a Double-Blind Study? | Introduction & Examples

Published on 6 May 2022 by Lauren Thomas . Revised on 17 October 2022.

In experimental research , subjects are randomly assigned to either a treatment or control group . A double-blind study withholds each subject’s group assignment from both the participant and the researcher performing the experiment.

If participants know which group they are assigned to, there is a risk that they might change their behaviour in a way that would influence the results. If researchers know which group a participant is assigned to, they might act in a way that reveals the assignment or directly influences the results.

Double blinding guards against these risks, ensuring that any difference between the groups can be attributed to the treatment.

Table of contents

Different types of blinding, importance of blinding, frequently asked questions about double-blind studies.

Blinding means withholding which group each participant has been assigned to. Studies may use single, double or triple blinding.

Single blinding occurs in many different kinds of studies, but double and triple blinding are mainly used in medical research.

Single blinding

If participants know whether they were assigned to the treatment or control group, they might modify their behaviour as a result, potentially changing their eventual outcome.

In a single-blind experiment, participants do not know which group they have been placed in until after the experiment has finished.

If participants in the control group realise they have received a fake vaccine and are not protected against the flu, they might modify their behaviour in ways that lower their chances of becoming sick – frequently washing their hands, avoiding crowded areas, etc. This behaviour could narrow the gap in sickness rates between the control group and the treatment group, thus making the vaccine seem less effective than it really is.

Double blinding

When the researchers administering the experimental treatment are aware of each participant’s group assignment, they may inadvertently treat those in the control group differently from those in the treatment group. This could reveal to participants their group assignment, or even directly influence the outcome itself.

In double-blind experiments, the group assignment is hidden from both the participant and the person administering the experiment.

If these experimenters knew which vaccines were real and which were fake, they might accidentally reveal this information to the participants, thus influencing their behaviour and indirectly the results.

They could even directly influence the results. For instance, if experimenters expect the vaccine to result in lower levels of flu symptoms, they might accidentally measure symptoms incorrectly, thus making the vaccine appear more effective than it really is.

Triple blinding

Although rarely implemented, triple-blind studies occur when group assignment is hidden not only from participants and administrators, but also from those tasked with analysing the data after the experiment has concluded.

Researchers may expect a certain outcome and analyse the data in different ways until they arrive at the outcome they expected, even if it is merely a result of chance.

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Blinding helps ensure a study’s internal validity , or the extent to which you can be confident any link you find in your study is a true cause-and-effect relationship.

Since non-blinded studies can result in participants modifying their behaviour or researchers finding effects that do not really exist, blinding is an important tool to avoid bias in all types of scientific research.

Risk of unblinding

Unblinding occurs when researchers have blinded participants or experimenters, but they become aware of who received which treatment before the experiment has ended.

This may result in the same outcomes as would have occurred without any blinding.

You randomly assign some students to the new programme (the treatment group), while others are instructed with a standard programme (the control group). You use single blinding: you do not inform students whether they are receiving the new instruction programme or the standard one.

If students become aware of which programme they have been assigned to – for example, by talking to previous students about the content of the programme – they may change their behaviour. Students in the control group might work harder on their reading skills to make up for not receiving the new programme, or conversely to put in less effort instead since they might believe the other students will do better than them anyway.

Inability to blind

Double or triple blinding is often not possible. While medical experiments can usually use a placebo or fake treatment for blinding, in other types of research, the treatment sometimes cannot be disguised from either the participant or the experimenter. For example, many treatments that physical therapists perform cannot be faked.

In such cases, you must rely on other methods to reduce bias.

• Running a single- rather than double- or triple-blind study. Sometimes, although you might not be able to hide what each subject receives, you can still prevent them from knowing whether they are in the treatment or control group. Single blinding is particularly useful in non-medical studies where you cannot use a placebo in the control group.
• Relying on objective measures that participants and experimenters have less control over rather than subjective ones, like measuring fever rather than self-reported pain. This should reduce the possibility that participants or experimenters could influence the results.
• Pre-registering data analysis techniques. This will prevent researchers from trying different measures of analysis until they arrive at the answer they’re expecting.

Blinding means hiding who is assigned to the treatment group and who is assigned to the control group in an experiment .

Blinding is important to reduce bias (e.g., observer bias , demand characteristics ) and ensure a study’s internal validity .

If participants know whether they are in a control or treatment group , they may adjust their behaviour in ways that affect the outcome that researchers are trying to measure. If the people administering the treatment are aware of group assignment, they may treat participants differently and thus directly or indirectly influence the final results.

• In a single-blind study , only the participants are blinded.
• In a double-blind study , both participants and experimenters are blinded.
• In a triple-blind study , the assignment is hidden not only from participants and experimenters, but also from the researchers analysing the data.

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Double Blind Study – Blinded Experiments

In science and medicine, a blind study or blind experiment is one in which information about the study is withheld from the participants until the experiment ends. The purpose of blinding an experiment is reducing bias, which is a type of error . Sometimes blinding is impractical or unethical, but in many experiments it improves the validity of results. Here is a look at the types of blinding and potentials problems that arise.

Single Blind, Double Blind, and Triple Blind Studies

The three types of blinding are single blinding, double blinding, and triple blinding:

Single Blind Study

In a single blind study , the researchers and analysis team know who gets a treatment, but the experimental subjects do not. In other words, the people performing the study know what the independent variable is and how it is being tested. The subjects are unaware whether they are receiving a placebo or a treatment. They may even be unaware what, exactly, is being studied.

Example: Violin Study

For example, consider an experiment that tests whether or not violinists can tell the difference a Stradivarius violin (generally regarded as superior) and a modern violin. The researchers know the type of violin they hand to a violinist, but the musician does not (is blind). In case you’re curious, in an actual experiment performed by Claudia Fritz and Joseph Curtin, it turned out violinists actually can’t tell the instruments apart.

Double Blind Study

In a double blind study, neither the researchers nor subjects know which group receives a treatment and which gets a placebo .

Example: Drug Trial

Many drug trials are double-blinded, where neither the doctor nor patient knows whether the drug or a placebo is administered. So, who gets the drug or the placebo is randomly assigned (without the doctor knowing who gets what). The inactive ingredients, color, and size of a pill (for example) are the same whether it is the treatment or placebo.

Triple Blind Study

A triple blind study includes an additional level of blinding. So, the data analysis team or the group overseeing an experiment is blind, in addition to the researchers and subjects.

Example: Vaccine Study

Triple blind studies are common as part of the vaccine approval process. Here, the people who analyze vaccine effectiveness collate data from many test sites and are unaware of which group a participant belongs to.

Some guidelines advocate for removing terms like “single blind” and “double blind” because they do not inherently describe which party is blinded. For example, a double blind study could mean the subjects and scientists are blind or it could mean the subjects and assessors are blind. When you describe blinding in an experiment, report who is blinded and what information is concealed.

The point of blinding is minimizing bias. Subjects have expectations if they know they receive a placebo versus a treatment. And, researchers have expectations regarding the expected outcome. For example, confirmation bias occurs when an investigator favors outcomes that support pre-existing research or the scientist’s own beliefs.

Unblinding is when masked information becomes available. In experiments with humans, intentional unblinding after a study concludes is typical. This way, a subject knows whether or not they received a treatment or placebo. Unblinding after a study concludes does not introduce bias because the data has already been collected and analyzed.

However, premature unblinding also occurs. For example, a doctor reviewing bloodwork often figures out who is getting a treatment and who is getting a placebo. Similarly, patients feeling an effect from a pill or injection suspect they are in the treatment group. One safeguard against this is an active placebo. An active placebo causes side effects, so it’s harder to tell treatment and placebo groups apart just based on how a patient feels.

Although premature unblinding affects the outcome of the results, it isn’t usually reported. This is a problem because unintentional unblinding favors false positives, at least in medicine. For example, if subjects believe they are receiving treatment, they often feel better even if a therapy isn’t effective. Premature unblinding is one of the issues at the heart of the debate about whether or not antidepressants are effective. But, it applies to all blind studies.

Uses of Blind Studies

Of course, blind studies are valuable in medicine and scientific research. But, they also have other applications.

For example, in a police lineup, having an officer familiar with the suspects can influence a witness’s selection. A better option is a blind procedure, using an office who does not know a suspect’s identity. Product developers routinely use blind studies for determining consumer preference. Orchestras use blind judging for auditions. Some employers and educational institutions use blind data for application selection.

• Bello, Segun; Moustgaard, Helene; Hróbjartsson, Asbjørn (October 2014). “The risk of unblinding was infrequently and incompletely reported in 300 randomized clinical trial publications”. Journal of Clinical Epidemiology . 67 (10): 1059–1069. doi: 10.1016/j.jclinepi.2014.05.007
• Daston, L. (2005). “Scientific Error and the Ethos of Belief”. Social Research . 72 (1): 18. doi: 10.1353/sor.2005.0016
• MacCoun, Robert; Perlmutter, Saul (2015). “Blind analysis: Hide results to seek the truth”. Nature . 526 (7572): 187–189. doi: 10.1038/526187a
• Moncrieff, Joanna; Wessely, Simon; Hardy, Rebecca (2018). “Meta-analysis of trials comparing antidepressants with active placebos”. British Journal of Psychiatry . 172 (3): 227–231. doi: 10.1192/bjp.172.3.227
• Schulz, Kenneth F.; Grimes, David A. (2002). “Blinding in randomised trials: hiding who got what”. Lancet . 359 (9307): 696–700. doi: 10.1016/S0140-6736(02)07816-9

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Double-Blind, Placebo-Controlled Clinical Trial Basics

A clinical trial is one that involves human participants and seeks to answer specific questions about a type of medical intervention. This can be a drug or other type of treatment, such as nutritional changes or massage.

Double Blind

In the context of a clinical trial , double-blind   means that neither the patients nor the researchers know who is getting a placebo and who is getting the treatment. Because patients don't know what they're getting, their belief about what will happen doesn't taint the results. Because the researchers don't know either, they can't hint to patients about what they're getting, and they also won't taint results through their own biased expectations about what the results will be.

If researchers do know who's getting the treatment but the participants do not, it's called a single-blind trial.

Placebo and Control Groups

A placebo is an inactive substance (often a sugar pill) given to a patient in place of medication.

In drug trials, a control group is given a placebo while another group is given the drug (or other treatment) being studied. That way, researchers can compare the drug's effectiveness against the placebo's effectiveness.  

Placebo-controlled refers to a control group receiving a placebo. This sets it apart from studies that simply give participants treatment and record the results.

Double-Blind Placebo-Controlled Clinical Trial

Thus, a double-blind, placebo-controlled clinical trial is a medical study involving human participants in which neither side knows who's getting what treatment and placebo are given to a control group.

Before getting to this stage, researchers often perform animal studies, clinical trials not involving a control group, and single-blind studies.

The highest-quality studies are also randomized, meaning that subjects are randomly assigned to placebo and intervention groups. The acronym DBRCT is commonly used for these types of studies.

Food and Drug Administration. Basics About Clinical Trials .

American Cancer Society. Placebo Effect .

American Cancer Society. Clinical Trials: What You Need to Know .

National Institutes of Health. The Basics .

By Adrienne Dellwo Dellwo was diagnosed with fibromyalgia in 2006 and has over 25 years of experience in health research and writing.

Double Blind Study (Definition + Examples)

The impact of many treatments can only be confirmed after their effect has been verified in a double-blind study.

What Is a Double-Blind Study? 

A double-blind study is an experiment where both researchers and participants are “blind to” the crucial aspects of the study, such as the hypotheses, expectations, or the allocation of subjects to groups. In double-blind clinical trials, neither the experimenters nor the participants are aware of who is receiving a treatment.

Why Do a Double-Blind Study?

The main purpose of double-blind studies is to minimize the effects of experimenter bias . In other words, the results of the research are less likely to be affected by external factors, such as the experimenters verbally or nonverbally communicating their assumptions about the treatment’s efficiency or the expectations of the participants.

Double-blind studies serve as an invaluable scientific method in the pharmaceutical industry trials where they are regularly used for determining the impact of new medications. Double-blind studies are the very foundation of modern evidence-based medicine. They are often referred to as the gold standard for testing medications, that is, the most accurate test available. 

While they are best known for their application in medicine, double-blinded studies are widely used to validate theories and ideas in many other fields including agriculture, biology, chemistry, engineering, forensics, and social sciences. 

Example of Double-Blind Study

Identifying successful treatments is a complex procedure. Let’s say that a physician prescribes a new medication to a patient. After taking the medication, the patient reports improvement in his or her condition. Yet this doesn’t simply mean that the treatment is effective. In fact, in many cases patients will see improvements even when they are not taking active medication. 

In order to properly test the medication, a double-blind study will have to take place in which the experimenter (acting as the physician) administers either the medication or a placebo to the participant (acting as the patient). Only a third-party knows whether the medication was real or not. The participant's answers about their treatment will be recorded and sent to that third party.

Double-blind studies aren't just used to test new medication. A double-blind study was used to see if airport security dogs could sniff out COVID!

Double-Blind Studies and Placebo Effect

The placebo effect is a crucial component of double-blind studies. 

A placebo is an inactive substance that has no effect on the individual who is taking it. It looks just like the medication that is being tested so that the participants can’t say whether they are receiving the treatment or not. 

How to Conduct a Double-Blind Study

Subjects in double-blind studies are typically divided into three different groups: treatment or experimental group, placebo group, and control group. 

Participants who are not receiving any treatment are placed in the control group. This group serves as a baseline for determining whether the medication in question has any significant effects. If the control group gets better over time, then this improvement will set a standard against which the other two groups are compared. 

People placed in the treatment group are given the actual medication, while subjects in the placebo group are offered a placebo pill. Neither the participants in the treatment and placebo groups nor the experimenters have the information on who is receiving the real drug.

At the end of the trial, data collected from the groups are compared to determine if the treatment had the expected outcome. If subjects in the placebo group fare better than the control group, this positive development can be attributed to the participants’ belief that the pill works. But if people in the treatment group improve more than those in the placebo one, then the results can be attributed to the effect of the medication.

Other Types of Blind Studies

Several different types of blind studies are being used in research, such as double-blind comparative studies, single-blind studies, and triple-blind studies.

Double-blind comparative studies

In double-blind comparative studies, one group of participants is given a standard drug instead of a placebo. These studies compare the effects of new medicine and an old one whose impact has already been proven. This kind of study is useful in determining whether a new treatment is more effective than the existing one. 

Single-blind studies

In single-blind studies, only the participants are not informed whether they are receiving the real treatment. The experimenters, on the other hand, know which participants belong to which group.  

Triple-blind studies

Triple-blind studies are clinical trials in which knowledge about the treatment is hidden not only from subjects and experimenters but also from anyone involved in organizing the study and data analysis. 

Limitations of Double-Blind Studies

Despite their significance, double-blind studies hold a number of limitations and are not applicable to every type of research.

Number of Participants

To be effective, a double-blind study must include at least 100 participants and preferably as many as 300. Although effective treatments can also be proven in some small-scale trials, many double-blind studies are too limited in size to provide a representative sample and establish meaningful patterns. Studies involving fewer than 30 participants generally can't provide proof of a theory. 

Types of Double-Blind Studies 

Double blinding is not feasible in all types of trials. For instance, it is not possible to design studies on therapies such as acupuncture, physical therapy, diet, or surgery in a double-blind manner. In these cases, researchers and participants can’t be kept unaware of who is receiving therapy .

Nocebo Effect

Participants in clinical trials must be informed of the possible side effects that may result from the experimental treatment. However, the mere suggestion of a negative outcome may lead to the adverse placebo effect, also known as the nocebo effect. It can result in participant dropouts and the need for additional medications to treat the side effects.

In research, the use of a placebo is acceptable only in situations when there is no proven acceptable treatment for the condition in question. For ethical reasons, participants must always be informed of the possibility that they will be given a placebo. As a consequence, some participants may think that they feel the effects of the placebo, which makes them believe that they are in the treatment group. This high positive expectancy is a disadvantage that can lead to a misinterpretation of the results.

Costs of Double-Blind Studies

Double-blind procedures are very expensive. They may take several months to complete, as experiments often require numerous trials using different groups in order to collect enough data. As a result, double-blind studies can cost up to several million dollars, depending on the amount of work required and the industry in which the product is being tested.

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Double-Blind Study

• Reference work entry
• First Online: 01 January 2021
• pp 1517–1518
• Cite this reference work entry

• Lawrence David Scahill 2 , 3 , 4  

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DOUBLE-BLIND TRIAL. The double-blind trial is a research method that attempts to reduce the bias in research studies. In the classic double-blind trial, subjects are randomly assigned to receive an active medication or a placebo. The placebo is formulated to look and perhaps even taste like the active medication – but the placebo contains no active ingredients. We use the term “double-blind” to indicate that investigators and patients (and parents) do not know whether the patient is getting the active medication or the placebo. The treatment mask is intended to reduce bias and expectation.

When a new medication is being introduced, there may be a lot of interest and hope for the new medication. In the absence of placebo control, this interest and hope could lead to false impressions about the benefits of the medication. Indeed, high expectations can also contribute to the so-called “placebo effect.” In several recent studies in children with autism spectrum disorders, as...

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Vitiello, B., & Scahill, L. (2011). Clinical trials methdology and design. In A. Martin, L. Scahill, & C. Kratochvil (Eds.), Pediatric psychopharmacology: Principles and practice (pp. 711–724). New York: Oxford University Press.

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Lawrence David Scahill

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Scahill, L.D. (2021). Double-Blind Study. In: Volkmar, F.R. (eds) Encyclopedia of Autism Spectrum Disorders. Springer, Cham. https://doi.org/10.1007/978-3-319-91280-6_1235

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What is a Double-Blind Trial?

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When drugs or vaccines are being trialed for their effectiveness, there are typically several stages. Double-blind trials are seen as the most reliable type of study because they involve neither the participant nor the doctor knowing who has received what treatment. The aim of this is to minimize the placebo effect and minimize bias.

How they work

In double-blind trials, the treatment patients have is unknown to both patients and doctors until after the study is concluded. This differs from other types of trials, such as simple blind trials where only the patients are unaware of the treatment they are receiving, whereas the doctors know.

Double-blind trials are a form of randomized trials and can be ‘upgraded’ to triple-blind trials, in which the statisticians or data clean-up personnel are also blind to treatments.

To be effective, it is generally recommended that double-blind trials include around 100-300 people. If treatments are highly effective, smaller numbers can be used but if only 30 or so patients are enrolled the study is unlikely to be beneficial.

The assignment of patients into treatments is typically done by computers, where the computer assigns each patient a code number and treatment group. The doctor and patients only know the code number to avoid bias, hence allowing the study to be double-blind.

Double-blind trials can come in different varieties. Double-blind, placebo-controlled studies involve no one knowing the treatment assignments to remove the chance of placebo effects. In a double-blind comparative trial, a new treatment is often compared to the standard drug. This allows researchers to compare an established drug to a new one to establish which one is more advantageous.

However, unlike double-blind, placebo-controlled trials, they are not very good at statistically evaluating if a treatment is effective overall.

Benefits of double-blind trials

Double-blind trials remove any power of suggestion, as no one involved knows the treatment patients receive. This means that doctors carrying out the study do not know and cannot accidentally tip off participants. Similarly, the doctors not being aware of the treatments means they do not unconsciously bias their interpretation of the study results.

The main principle behind double-blind and randomized trials, as opposed to simple blind trials, is to avoid bias in the treatment or experimental set-up. For example, if researchers are aware of the different treatment groups are getting, they may avoid assigning more unwell patients to the treatment group. Therefore, any effect seen by the treatment may have been related to how unwell a patient was to start with, rather than the efficacy of the drug.

COVID-19 and double-blind trials

Double-blind trials are usually needed for drugs and treatments to get approval to be used in many countries. However, good, comprehensive double-blind trials take time and require many participants. This has been especially problematic during the COVID-19 pandemic, as the world has searched for pharmaceutical treatment options to improve survival and for vaccines to prevent the spread of this virus.

In terms of treatment, many drugs have been tested in double-blind trials. The antiviral nucleoside analog remdesivir has been tested in several double-blind trials and was the first drug to gain full FDA approval for use against COVID-19 in October 2020.

However, the results of trials have been conflicting, and some experts remained unconvinced of its benefits. In November 2020, the World Health Organization recommended against the use of the drug for COVID-19 and a global randomized trial came to the conclusion in February 2021 that remdesivir has little to no effect when used on hospitalized COVID-19 patients. The drug is still used in the US.

Multiple candidates for a COVID-19 vaccine have been identified and moved on to phase II and phase III trials, which often involve double-blind methods. These need to be conducted over meaningful timeframes to ensure any initial differences between the control and the treatment groups last in the long term.

Several different vaccines are now available (March 2021) due to mixed approval and emergency approval by governments and organizations. This has been an exceptional time for vaccine trials as the typical course of development has been sped up. What would usually take years has taken months.

Many countries have given limited or early approval to vaccines for emergency use before detailed phase III data has been publicized, based on preliminary evidence of effectivity and safety. This comes with some risks.

Another topic of discussion that has come about as a result of COVID-19 is the ethics of keeping patients blind during the trial as vaccine effectivity is supported. Whilst keeping the blind aspect is essential to achieving valuable and reliable information about long-term effects, there is an argument that blind participants who have received a placebo should be able to receive a vaccine as more become available.

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Last Updated: Mar 19, 2021

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The double-blind, randomized, placebo-controlled trial: gold standard or golden calf?

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The double-blind randomized controlled trial (RCT) is accepted by medicine as objective scientific methodology that, when ideally performed, produces knowledge untainted by bias. The validity of the RCT rests not just on theoretical arguments, but also on the discrepancy between the RCT and less rigorous evidence (the difference is sometimes considered an objective measure of bias). A brief overview of historical and recent developments in "the discrepancy argument" is presented. The article then examines the possibility that some of this "deviation from truth" may be the result of artifacts introduced by the masked RCT itself. Can an "unbiased" method produce bias? Among the experiments examined are those that augment the methodological stringency of a normal RCT in order to render the experiment less susceptible to subversion by the mind. This methodology, a hypothetical "platinum" standard, can be used to judge the "gold" standard. The concealment in a placebo-controlled RCT seems capable of generating a "masking bias." Other potential biases, such as "investigator self-selection," "preference," and "consent" are also briefly discussed. Such potential distortions indicate that the double-blind RCT may not be objective in the realist sense, but rather is objective in a "softer" disciplinary sense. Some "facts" may not exist independent of the apparatus of their production.

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What Is a Double Blind Experiment?

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In many experiments, there are two groups: a control group and an experimental group . The members of the experimental group receive the particular treatment being studied, and the members of the control group do not receive the treatment. Members of these two groups are then compared to determine what effects can be observed from the experimental treatment. Even if you do observe some difference in the experimental group, one question you may have is, “How do we know that what we observed is due to the treatment?”

When you ask this question, you are really considering the possibility of lurking variables . These variables influence the response variable but do so in a way that is difficult to detect. Experiments involving human subjects are especially prone to lurking variables. Careful experimental design will limit the effects of lurking variables. One particularly important topic in the design of experiments is called a double-blind experiment.

Humans are marvelously complicated, which makes them difficult to work with as subjects for an experiment. For instance, when you give a subject an experimental medication and they exhibit signs of improvement, what is the reason? It could be the medicine, but there could also be some psychological effects. When someone thinks they are being given something that will make them better, sometimes they will get better. This is known as the placebo effect .

To mitigate any psychological effects of the subjects, sometimes a placebo is given to the control group. A placebo is designed to be as close to the means of administration of the experimental treatment as possible. But the placebo is not the treatment. For example, in the testing of a new pharmaceutical product, a placebo could be a capsule that contains a substance that has no medicinal value. By use of such a placebo, subjects in the experiment would not know whether they were given medication or not. Everyone, in either group, would be as likely to have psychological effects of receiving something that they thought was medicine.

Double Blind

While the use of a placebo is important, it only addresses some of the potential lurking variables. Another source of lurking variables comes from the person who administers the treatment. The knowledge of whether a capsule is an experimental drug or actually a placebo can affect a person’s behavior. Even the best doctor or nurse may behave differently toward an individual in a control group versus someone in an experimental group. One way to guard against this possibility is to make sure that the person administering the treatment does not know whether it is the experimental treatment or the placebo.

An experiment of this type is said to be double blind. It is called this because two parties are kept in the dark about the experiment. Both the subject and the person administering the treatment do not know whether the subject in the experimental or control group. This double layer will minimize the effects of some lurking variables.

Clarifications

It is important to point out a few things. Subjects are randomly assigned to the treatment or control group, have no knowledge of what group they are in and the people administering the treatments have no knowledge of which group their subjects are in. Despite this, there must be some way of knowing which subject is in which group. Many times this is achieved by having one member of a research team organize the experiment and know who is in which group. This person will not interact directly with the subjects, so will not influence their behavior.

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• Double Blind Studies in Research: Types, Pros & Cons

In the medical field, it is unethical to not inform your patient of a process or a procedure you want to carry out on them. It is required that the patients are informed about the treatment they would be given and that they consent to it. 

However, there is a method known as the blind study in psychological research.  A blind study prevents the participants from knowing about their treatment to avoid bias in the research.

This article will focus on the double-blind study which is a type of blind study which leaves both the researcher and the participants in the dark about important details of the study . That way the research is expected to be bias-free and far from any external influence.

The blind study has no ground in patient-doctor physical therapy sessions, but it is very helpful in other studies such as pharmacological research.

This is why we will consider a double-blind study, its usefulness, advantages, and disadvantages in a study or research. 

What is a Blinded Study?

A blinded study is research conducted in a way that prevents the subjects ( blind the subjects) from knowing the treatment they are given so that the researcher is guaranteed a biased free result. Information that can influence the subjects of a research is withheld from the subjects until the completion of the research.

If good blinding is carried out on the subjects, it can eliminate any form of biases that may arise from the subjects’ expectations, influence from the researcher, researcher’s bias , and other forms of biases that may occur in a research test.

This can be achieved as a blind study can be imposed on all participants in research. From the researcher to the subjects, the analysts, and even the judges or evaluators.

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In some cases, however, imposing blind study in research may be impossible or even unethical. For example, it is unethical for a medical practitioner to blind a patient from knowing their treatment. The ethical thing to do is let your patient be informed about a major part of their treatment if it’s in a face-to-face intervention.

A subject can become unblinded during a study if they obtain information that has been previously shielded away from them. For example, if due to experiencing some side effects symptoms, a subject could correctly guess the treatment he/she has been exposed to. The subject then becomes unblinded. Subjects becoming unblinded mostly occur in pharmacological testings. 

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What is a Double-blind Study?

Double-blind refers to a study or research where both the subjects or participants of a study and the researchers are oblivious of the treatment being given and the subjects receiving the treatment. Both the participants and the experimenter are kept in the dark. This is done to eliminate all presence of biases in the outcome of the research.

It is most useful in research because of the placebo effect.

For example, if a researcher wants to conduct research on the effects of a newly introduced drug . A double-blind study requires that both the researcher and the subjects are unaware of the process.

So the researcher that is analyzing the subjects would have no information about the subjects receiving the new drug (which is the treatment group) and those who are not receiving the drug (which is the control group).

Now if the participants are not aware of their treatment and the researcher is not provided with information on who is receiving the treatment, the question that requires an answer is, why is a double-blind study needed?

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Purpose of a Double-blinded Study

Every procedure has its purpose and a double-blind study is not left out. The purpose of a double-blind study is to make sure that the outcomes of a study are free from biases. Using the double-blind method in a study improves the level of credibility and validity of the study 

A double-blind study is used in the scientific field, psychologists, and also in the legal process.

Read more: What are Cross-Sectional Studies: Examples, Definition, Types

Types of Blinded Studies

There are three types of blind studies namely single-blind study, double-blind study, and triple-blind study

1. Single-blind study : in this type of blind study only the subjects in the experiment are prevented from knowing the treatment they are given. The single-blind study is also known as the single masked study.

2. Double-blind study:   In the double-blind study both the subjects or participants and the researcher are blinded.  The researcher is unaware of who is receiving what treatment and the participants are unaware of the treatment they are receiving.

3. Triple blind study : here in the triple-blind study the participants, the researcher analyzing data , and the data collector are blinded from the information about the study. These three groups are prevented from knowing the treatments being given out or being received.

When to Use Each Type of Blind Study

Now that we know the types of blind study we are going to consider when it is appropriate to use either of these types of blind study in research.

• When to use a single-blind study

A single-blind study is usually conducted to prevent the subject from being aware of the treatment being studied. This is in case they get influenced and that leads to bias in the outcome.

It should be noted that there are cases where blinding a participant or patient is considered unethical. Therefore, single-blind study should only be used in statistical research or studies that don’t involve physical therapy between a patient and a doctor.

• When to use a double-blind study

Double-blind study is conducted when both the participants and the researcher are not allowed to know details of the research. This process is used to prevent bias in the study results and when there is a need to understand the characteristics of the results or to understand placebo effect.

• When to use a triple-blind study :

Use triple blind study if you aim to reduce your study and improve the accuracy of your results. This is because a triple-blind study allows randomization where the treatment item and the intervention are not known to the participants, researcher, data collector , or clinical personnel.

Read: Survey Errors To Avoid: Types, Sources, Examples, Mitigation

Advantages of Double-blinded Study

The following are the advantages of double-blind study:

1. It tests for three groups

The double-blind study usually involves three groups of subjects. The first is the treatment group, then the placebo, and lastly, the control group. The treatment group and the placebo are given the test item even though the researcher wouldn’t know which group is getting the treatment. No test item is administered to the control group because they are used as a basis of comparison for the results of the treatment group and the placebo.

If there’s a significant improvement in the placebo group over the control group, then it is considered that the treatment administered worked.

2. Reduces experimental bias

A double-blind study reduces the risk of biases in research. Biases can occur when a researcher influences the outcome of a study directly or otherwise. However, because the researcher is often also in the dark, it is difficult to influence the study.

This allows for credible, reliable, and valid research results.

3. Result duplication

The results of a double-blind study can be duplicated and that is why this procedure is considered one of the best practices. A double-blind study allows other researchers to follow up with the same processes, apply the test item, and compare the result with the control group.

The usefulness of this method is that if the results from these studies are close, it proves the validity of the test item that was administered. If there is no duplication in the research results, another study has to be carried out to determine why.

Disadvantages of a Double-Blind Study

1. it is expensive.

One huge disadvantage of a double-blind study is that it is expensive to conduct. It takes several months or years to complete because the researcher has to examine all the possible variables and they may have to use different groups to gather enough data. 

Many corporations after estimating the cost of this study which runs into millions of Dollars might have to spread the research across multiple months. Even for government studies, conducting this study may run into billions of dollars thereby making the medicine expensive in the market. This is one of the reasons why new prescription medicines are sold at an expensive price in the market.

2. Low representation

A double-blind study cannot provide a properly represented sample group because it is small. Most double-blind study is designed to enroll at least 100 people or participants for the research however the most preferable number is 300. It is true that the effectiveness of a treatment can be proven even in small studies but more people or participants are required to determine a pattern in research so that the results can be properly analyzed and verified.

Research generally requires participants in large numbers to participate in the trials and progress of a treatment being administered or in plan to be introduced to the market.

This is because even when the product or treatment item has gotten to the third phase of testing it still has only a 60% chance to proceed to another stage.

3. Negative reaction

In some cases some of the participants may react negatively to the treatment item when this happens the results from the test can be compared to see what changed. Some participants may react negatively to the placebo which may lead to producing some side effects that may make it seem like they were receiving the treatment item when they did not.

4. Time factor

Many times it is almost impossible to complete a double-blind study. For example, you cannot keep the subject or participants of a psychotherapy experiment in the dark about who gets the treatment item and who doesn’t get the treatment item. Double-blind study can only work in this scenario if you find a way to provide two similar procedures without each of the groups communicating about which group is getting the treatment item and which group is getting the placebo.

Frequently Asked Questions about Blind Studies

• Which is better: single-blind or double-blind study?

To determine which is best between a single-blind study and a double-blind study the case being studied has to be considered.

For example, if a researcher is conducting a study on the effects of a medicine that can cure Alzheimer’s, it is best to use a double-blind study rather than a single-blind study. This is because the participants will be unaware if they received the treatment item from the real drug or if they received the placebo which in turn reduces any external influence on the results of the test.

• When would you use a single-blind study?

Use a single-blind study if the participants having knowledge of the group they belong to might result in bias. I.e. whether their being aware of the treatment item and the questions of the study might result in bias.

• What is the difference between a single and double-blind study?

The significant difference between a single study and a double-blind study is that in a single-blind study only the participants or the patient are blinded while in a double-blind study both the participant and the researcher are blinded.

In any study, it is good to know how the results of the treatment group and the response group compare in an experiment. This is why a double-blind study is important. 

The risk of anyone manipulating data or influencing the participants is averted since a double-blind study prevents both the researcher or the participants from obtaining in-depth knowledge of the study.

You can be assured that the researcher cannot accidentally communicate with the subjects or participants. Now that is one huge importance and psychological benefit of the placebo effect.

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Blinding in clinical trials and other studies

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• Simon J Day a , manager, clinical biometrics ,
• Douglas G Altman b , professor of statistics in medicine
• a Leo Pharmaceuticals, Princes Risborough, Buckinghamshire HP27 9RR
• b ICRF Medical Statistics Group, Institute of Health Sciences, Oxford OX3 7LF
• Correspondence to: S J Day

Human behaviour is influenced by what we know or believe. In research there is a particular risk of expectation influencing findings, most obviously when there is some subjectivity in assessment, leading to biased results. Blinding (sometimes called masking) is used to try to eliminate such bias.

It is a tenet of randomised controlled trials that the treatment allocation for each patient is not revealed until the patient has irrevocably been entered into the trial, to avoid selection bias. This sort of blinding, better referred to as allocation concealment, will be discussed in a future statistics note. In controlled trials the term blinding, and in particular “double blind,” usually refers to keeping study participants, those involved with their management, and those collecting and analysing clinical data unaware of the assigned treatment, so that they should not be influenced by that knowledge.

The relevance of blinding will vary according to circumstances. Blinding patients to the treatment they have received in a controlled trial is particularly important when the response criteria are subjective, such as alleviation of pain, but less important for objective criteria, such as death. Similarly, medical staff caring for patients in a randomised trial should be blinded to treatment allocation to minimise possible bias in patient management and in assessing disease status. For example, the decision to withdraw a patient from a study or to adjust the dose of medication could easily be influenced by knowledge of which treatment group the patient has been assigned to.

In a double blind trial neither the patient nor the caregivers are aware of the treatment assignment. Blinding means more than just keeping the name of the treatment hidden. Patients may well see the treatment being given to patients in the other treatment group(s), and the appearance of the drug used in the study could give a clue to its identity. Differences in taste, smell, or mode of delivery may also influence efficacy, so these aspects should be identical for each treatment group. Even colour of medication has been shown to influence efficacy. 1

In studies comparing two active compounds, blinding is possible using the “double dummy” method. For example, if we want to compare two medicines, one presented as green tablets and one as pink capsules, we could also supply green placebo tablets and pink placebo capsules so that both groups of patients would take one green tablet and one pink capsule.

Blinding is certainly not always easy or possible. Single blind trials (where either only the investigator or only the patient is blind to the allocation) are sometimes unavoidable, as are open (non-blind) trials. In trials of different styles of patient management, surgical procedures, or alternative therapies, full blinding is often impossible.

In a double blind trial it is implicit that the assessment of patient outcome is done in ignorance of the treatment received. Such blind assessment of outcome can often also be achieved in trials which are open (non-blinded). For example, lesions can be photographed before and after treatment and assessed by someone not involved in running the trial. Indeed, blind assessment of outcome may be more important than blinding the administration of the treatment, especially when the outcome measure involves subjectivity. Despite the best intentions, some treatments have unintended effects that are so specific that their occurrence will inevitably identify the treatment received to both the patient and the medical staff. Blind assessment of outcome is especially useful when this is a risk.

In epidemiological studies it is preferable that the identification of “cases” as opposed to “controls” be kept secret while researchers are determining each subject's exposure to potential risk factors. In many such studies blinding is impossible because exposure can be discovered only by interviewing the study participants, who obviously know whether or not they are a case. The risk of differential recall of important disease related events between cases and controls must then be recognised and if possible investigated. 2 As a minimum the sensitivity of the results to differential recall should be considered. Blinded assessment of patient outcome may also be valuable in other epidemiological studies, such as cohort studies.

Blinding is important in other types of research too. For example, in studies to evaluate the performance of a diagnostic test those performing the test must be unaware of the true diagnosis. In studies to evaluate the reproducibility of a measurement technique the observers must be unaware of their previous measurement(s) on the same individual.

We have emphasised the risks of bias if adequate blinding is not used. This may seem to be challenging the integrity of researchers and patients, but bias associated with knowing the treatment is often subconscious. On average, randomised trials that have not used appropriate levels of blinding show larger treatment effects than blinded studies. 3 Similarly, diagnostic test performance is overestimated when the reference test is interpreted with knowledge of the test result. 4 Blinding makes it difficult to bias results intentionally or unintentionally and so helps ensure the credibility of study conclusions.

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Clinical trials are the basis of many experiments and they are crucial to finding new ways to help people manage and treat their diseases and conditions. Clinical trials are part of just about every research that involves a human subject, and the importance of those studies helps researchers determine how safe and effective a product or idea is before it goes on the market for billions of potential users.

To ensure the validity of the results, many times a single or double-blind study is used. These methods of research and data collection keep the experiment in check, weighing a placebo group against those engaging in the actual research in question. Whether to use a single-blind or double-blind study depends on what is being analyzed.

The Ethics and Legalities of Human Research Experiments

It only takes going back less than one hundred years to see that humans make a lot of mistakes in the search for knowledge. Reviewing the history of how researchers have used people to determine the validity of a research idea can be a cringe-worthy experience that helps us realize the importance behind our ethical and legal codes that must be followed today.

Informed consent is now required before any human is allowed to participate in a research study, as a direct result of documents such as the Nuremberg Code, the Declaration of Helsinki, and the Belmont Report. No matter how difficult or cumbersome it may be to obtain such consent, understanding the circumstances around these events makes it apparent why the strict requirements are necessary.

Beginning in 1947 with the Nuremberg Code, the question of how humans were treated in research became a global topic. The Code was developed because of the inhumane treatment of humans by Nazi doctors who used them immorally and unethically to answer their questions of research. The Nuremberg Code required that all human participants in a study must voluntarily agree to be involved. The term ‘voluntarily’ meant that there was no coercion behind the consent, the person was mentally and physically able to agree to the study, and they understood the risks entailed.

Then, in 1964, this was taken a bit further with the Declaration of Helsinki. Twelve principles were used to guide researchers as to how to ethically work through biomedical research with the innovation of technology. These principles focused on research being performed that would benefit the participant instead of knowledge that could help in the future.

From there, the Belmont Report of 1979 was established, adding that even with voluntary consent as in the Nuremberg Code, humans must be treated respectfully. This was particularly important for people who had less autonomy, such as children and the elderly.

What are Single and Double-Blind Studies?

In clinical trials, there are two models that researchers will follow to complete their experiments: the single blind and the double-blind trial. Using the right trial has a direct effect on the results and can bring up any errors ahead of time to reduce problems. The model the researchers use depends on the type of trial they are performing and a host of variables that are included in that study.

A clinical trial includes two groups of people involved in the experiment. One group is always the placebo group, given a placebo that looks like the treatment. The other group is given the treatment itself. Both groups are monitored for a specific list of results and are compared to each other to determine how effective the treatment was versus the placebo.

Single-blind studies work in that those who participate in the trial don’t know if they’re getting the placebo or the real thing. With this “blind” idea to the experiment, there are fewer chances of errors. The participants can’t doctor their results since they aren’t sure if they’re getting the real treatment or not. However, the monitoring experiment researcher knows which participants got the placebo and which received the treatment.

A double-blind study, on the other hand, includes an experiment in which neither the participants nor the research experimenter knows who got the actual treatment. Because of the fact that the researcher doesn’t know who got what treatment during the study, there is less of a chance of bias being introduced. This is, therefore, considered the optimal method of clinical research.

When you determine which method is better for your study, it’s often best to err on the side of too much caution to improve the accuracy of your results.

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Double Blind Experiment

A double blind experiment is an experimental method used to ensure impartiality, and avoid errors arising from bias.

This article is a part of the guide:

• Experimental Research
• Pretest-Posttest
• Third Variable
• Research Bias
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Browse Full Outline

• 1 Experimental Research
• 2.1 Independent Variable
• 2.2 Dependent Variable
• 2.3 Controlled Variables
• 2.4 Third Variable
• 3.1 Control Group
• 3.2 Research Bias
• 3.3.1 Placebo Effect
• 3.3.2 Double Blind Method
• 4.1 Randomized Controlled Trials
• 4.2 Pretest-Posttest
• 4.3 Solomon Four Group
• 4.4 Between Subjects
• 4.5 Within Subject
• 4.6 Repeated Measures
• 4.7 Counterbalanced Measures
• 4.8 Matched Subjects

It is very easy for a researcher, even subconsciously, to influence experimental observations, especially in behavioral science, so this method provides an extra check.

For example, imagine that a company is asking consumers for opinions about its products, using a survey .

There is a distinct danger that the interviewer may subconsciously emphasize the company's products when asking the questions. This is the major reason why market research companies generally prefer to use computers, and double blind experiments, for gathering important data.

The Blind Experiment

The blind experiment is the minimum standard for any test involving subjects and opinions, and failure to adhere to this principle may result in experimental flaws.

The idea is that the groups studied, including the control , should not be aware of the group in which they are placed. In medicine, when researchers are testing a new medicine, they ensure that the placebo looks, and tastes, the same as the actual medicine.

There is strong evidence of a placebo effect with medicine, where, if people believe that they are receiving a medicine, they show some signs of improvement in health. A blind experiment reduces the risk of bias from this effect, giving an honest baseline for the research, and allowing a realistic statistical comparison.

Ideally, the subjects would not be told that a placebo was being used at all, but this is regarded as unethical.

The Double Blind Experiment

The double blind experiment takes this precaution against bias one step further, by ensuring that the researcher does not know in which group a patient falls.

Whilst the vast majority of researchers are professionals, there is always a chance that the researcher might subconsciously tip off a patient about the pill they were receiving. They may even favor giving the pill to patients that they thought had the best chance of recovery, skewing the results.

Whilst nobody likes to think of scientists as dishonest, there is often pressure, from billion dollar drug companies and the fight for research grants, to generate positive results.

This always gives a chance that a scientist might manipulate results, and try to show the research in a better light. Proving that the researcher carried out a double blind experiment reduces the chance of criticism.

Other Applications

Whilst better known in medicine, double blind experiments are often used in other fields. Surveys , questionnaires and market research all use this technique to retain credibility.

If you wish to compare two different brands of washing powder, the samples should be in the same packaging. A consumer might have an inbuilt brand identity awareness, and preference, which will lead to favoritism and bias.

An example of the weakness of single blind techniques is in police line-ups, where a witness picks out a suspect from a group. Many legal experts are advocating that these line-ups should be unsupervised, and unprompted.

If the police are fixed on bringing a particular subject to justice, they may consciously, or subconsciously, tip off the witness. Humans are very good at understanding body language and unconscious cues, so the chance of observer's bias should be minimized.

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Martyn Shuttleworth (Nov 14, 2008). Double Blind Experiment. Retrieved Aug 26, 2024 from Explorable.com: https://explorable.com/double-blind-experiment

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Recruitment, Retention, and Blinding in Clinical Trials

Stephen j. page.

Stephen J. Page, PhD, MS, MOT, OTR/L, FAHA, is Associate Professor and Director, Neuromotor Recovery and Rehabilitation Laboratory (the “Rehablab” ® ), Division of Occupational Therapy, Ohio State University Medical Center, 453 West Tenth Avenue, Suite 416, Columbus, OH 43210; [email protected]

Andrew C. Persch

Andrew C. Persch, MS, OTR/L, is Graduate Assistant, Division of Occupational Therapy, School of Health and Rehabilitation Sciences, and Graduate Student, Doctor of Philosophy in Health and Rehabilitation Sciences, Ohio State University Medical Center, Columbus

The recruitment and retention of participants and the blinding of participants, health care providers, and data collectors present challenges for clinical trial investigators. This article reviews challenges and alternative strategies associated with these three important clinical trial activities. Common recruiting pitfalls, including low sample size, unfriendly study designs, suboptimal testing locations, and untimely recruitment are discussed together with strategies for overcoming these barriers. The use of active controls, technology-supported visit reminders, and up-front scheduling is recommended to prevent attrition and maximize retention of participants. Blinding is conceptualized as the process of concealing research design elements from key players in the research process. Strategies for blinding participants, health care providers, and data collectors are suggested.

As noted by its originators, evidence-based practice ( EBP ) is typified by “the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients” ( Sackett, Rosenberg, Gray, Haynes, & Richardson, 1996 , p. 71). The concept of EBP has attracted widespread support among stakeholders interested in ensuring that interventions are safe, credible, and appropriate.

This growing commitment to ensuring that practice aligns with sound research findings poses challenges to occupational therapy practitioners. For example, “standard of care” occupational therapy practice has sometimes consisted of clinicians’ impressions of what works with their caseloads, information gained during a clinician’s academic or continuing education training, and the way a disorder has traditionally been addressed at the particular institution. Indeed, in the authors’ shared interest area of neurorehabilitation, conceptualizations about the etiology and treatment of certain disorders and personal investment in certain intervention strategies often significantly influence the selection of certain treatments. Although informative, the sole use of training, clinical judgment, and content expertise is insufficient to evaluate treatment efficacy or to act as the single basis for treatment guidelines. EBP can also be challenging for clinicians who do not have the training, comfort, time, or institutional support to search and integrate evidence into practice. To this end, Green, Gorenflo, and Wyszewianski (2002) reported considerable variability in the value and credibility that clinicians place on experiential versus empirical evidence and in their willingness to integrate new, empirically supported strategies into practice. Such reluctance can delay translation of promising therapies to clinical use.

Regardless of individual clinicians’ comfort with or use of EBP, one outcome of its increasing emphasis has been greater value placed on trials of intervention effectiveness. For example, the American Occupational Therapy Association (AOTA) Centennial Vision asserts that occupational therapy will emerge as an “evidence-based profession” ( AOTA, 2007 , p. 1). Likewise, AOTA and other allied health organizations (e.g., American Physical Therapy Association [APTA], American Congress of Rehabilitation Medicine) have deployed tools to ease the process of searching for evidence (e.g., APTA’s Hooked on Evidence Web site; focused “white papers,” podcasts, and position statements). For those of us involved in research, clinical trials constitute a tangible method of improving practice and increasing the validity of the occupational therapy profession by producing evidence that guides clinical decision making. Yet, an emphasis on clinical trials also creates unique challenges for professions that largely use behavioral interventions. For example, unlike a pharmacological intervention, a behavioral therapy is not easily controlled, and participants frequently know which intervention they are receiving. Moreover, clients receiving occupational therapy services are often undergoing myriad therapies. Collectively, these and other challenges make recruitment to occupational therapy intervention trials, the isolation of the active therapeutic ingredients, and blinding of participants difficult. This article discusses three of the most vexing challenges associated with occupational therapy behavioral trials: participant recruiting, participant retention, and blinding. Alternative strategies that have been used to overcome these challenges are also discussed.

Recruiting in Clinical Trials

Enrollment of the targeted number of participants is essential to conducting a successful clinical trial, primarily because adequate enrollment provides a basis for proving or disproving the study hypothesis. Enrollment of too few participants can result in an underpowered study, which can cause Type II errors. Additionally, a successful recruitment strategy provides an adequate pool of qualified participants in case a participant decides—or is asked—to withdraw from study participation.

Yet, despite its fundamental importance, successful participant recruitment is a frequent challenge. Although a goal of this article is to share effective recruitment strategies, a brief review of some of the pitfalls encountered during participant recruitment can also be instructive. These pitfalls and some of their alternative strategies are summarized in Table 1 .

Recruitment Challenges and Alternative Strategies

The number of participants needed to successfully answer the research question is usually established a priori. However, researchers may overlook the fact that although a high fraction of recruited participants successfully reach the enrollment phase, the numbers diminish by the end of pretesting, the end of the intervention phase, and follow-up visits. The principal investigator (PI) should expect that of the participants recruited, some will be screen failures (i.e., will not meet eligibility criteria), some will withdraw on their own, and others will be withdrawn by investigators because of noncompliance or adverse events. Investigators should specify a larger number of initial participants when writing their protocols. In our laboratory, we usually anticipate a 10% rate of study withdrawal and an additional 10% loss during follow-up.

Any study must be rigorously designed to accomplish aims and evaluate hypotheses. When conceptualizing studies, investigators must weigh the requirements of study participation against the toll that participation will exact on participants (e.g., time, mental or physical fatigue). For example, although designs using multiple endpoints and testing sessions may provide a more precise characterization of the intervention response, participants are unlikely to enter studies that involve procedures they find difficult to understand or that require multiple follow-ups. Concurrently, investigators also should consider the necessity of study criteria in designing the study.

On the one hand, inclusion and exclusion criteria are often advantageous because such criteria ensure a well-defined sample of participants and can be created in such a way as to exclude participants with sequelae that may undermine study participation. For instance, in our stroke trials, we often restrict participation to people within a relatively narrow age range; those who are much older or younger may respond differently to an intervention, thereby affecting the study’s internal validity. By keeping participants’ ages within a certain well-defined range, we reduce the likelihood of this extraneous variable affecting outcomes and reducing participant heterogeneity.

On the other hand, delimiting participant characteristics can have disadvantages, including reducing the generalizability of study findings to the general population. For example, if we narrowed the age range of eligible participants to include only younger people, our findings would be less likely to generalize to people who have had strokes, who tend to be older. Investigative teams must weigh the benefits of more versus less restrictive study criteria when initiating a trial. In our laboratory, we usually use more rigid and specific study criteria in our pilot work, when we are trying to affirm safety and efficacy and optimize study endpoints. We may then loosen some criteria as we progress to later and larger trials so that we can identify the participants most likely to respond to the intervention.

In designing their studies, investigators should consider pragmatic issues such as the following: Where will participants be encountered? Is the setting a place that they normally frequent at this point in the trajectory of the disease process? Is there a cost (e.g., parking) for the participant to matriculate to this place? Ideally, the investigator should anticipate where participants will prefer to be seen and minimize the perceived cost and effort associated with study participation to optimize successful recruitment. For example, the first author (Stephen Page) located one of his research laboratories at a rehabilitation hospital approximately 10 miles from his academic medical center. Although this distance created some occasional inconveniences, it positioned his team closer to potential participants. Consideration should also be given to the time point at which clients will likely receive services. For instance, if a trial requires inpatients, it will likely be suboptimal for the research team to be located in an outpatient facility. Expenses associated with all of the above arrangements could be placed in the advertising budget of supporting grants.

Too often, researchers wait until after the study period has begun to develop and implement a recruitment plan, which creates difficulties for a number of reasons. First, some aspects of a recruitment plan may require resources that take time to accumulate. For instance, in our laboratory, we often engage hospitals and clinics across the community as recruitment sites. Thus, we prefer to speak with administrators and clinicians well before the study starts. This strategy allows us to gain their buy in and gives them ample time to recruit candidates. Some aspects of the study may require time or financial resources (e.g., advertisements, supplies) or may require additional institutional review board (IRB) review. For these reasons, one of the authors (Page) scripts the recruiting strategy several months in advance of the trial’s start date, including a timeline that details recruitment activities, supplies needed for that action, and a responsible party for each activity. By being detailed and preemptive, researchers can be ready to recruit and expend their limited resources effectively when the study begins.

Although they do not fit neatly into one of the above categories, we wish to highlight two other points relating to recruiting. First, we have found that conducting pilot trials is useful in confirming the effectiveness of one’s recruitment strategies ( Loscalzo, 2009 ). Such trials allow the investigative team to experience and troubleshoot some of the above-described challenges on a smaller scale. For this reason, funding agencies are increasingly encouraging researchers to use pilot trials to perfect recruitment strategies, confirm intervention safety and efficacy, and optimize study endpoints.

Second, the equitable recruitment of minority populations, women, and children has become an important issue to funders. Ethnicity, gender, and ages of participants should thus be elucidated in the recruiting plan and logged by the study team. During the Advancing Clinical Trials and Outcomes Research (ACTOR) conference, one occupational therapy leader noted that of the more than 1,000 participants her team had recruited into clinical trials, more than 800 were from a single minority population. Researchers should use this as a cautionary reminder that a disproportionate number of participants from any single population is likely to undermine a study’s generalizability.

To our knowledge, we are the first to use the terms passive recruiting and active recruiting to describe the manner in which particular recruitment strategies engage potential participants. The term passive recruiting strategies loosely refers to strategies in which the research team makes an initial effort to gain participants’ attention (e.g., a centrally placed study advertisement), but the onus is largely on the participant to take action. Considered on a continuum with passive strategies, active recruiting strategies are typified by the investigative team taking a more active role in the recruiting process (e.g., providing community-based in-services). In our laboratory, we have found the use of a mix of passive and active strategies to be optimal, with more active strategies emphasized whenever possible. Examples of these strategies are depicted in Figure 1 .

Continuum of selected passive and active recruiting strategies.

* Requires a Health Insurance Portability and Accountability Act waiver or other special permissions.

Retention in Clinical Trials

Identifying participants and enrolling them in the trial do not conclude the investigative team’s responsibilities. Clinical trial teams must also be concerned with ensuring that participants adhere to all aspects of the study protocol (discussed elsewhere in this issue; see Persch & Page, 2013 ) and remain in the study (i.e., retention). Retention is important because participants who are enrolled but do not complete a trial (study attrition) can undermine the internal and external validity of the findings. Specifically, attrition can cause study results to be biased when participants are not lost randomly but have certain characteristics that sustain better or worse outcomes ( Britton, Murray, Bulstrode, McPherson, & Denham, 1995 ). Although some may argue that a priori randomization and intention-to-treat analysis methods overcome this issue, they cannot account for nonrandom treatment termination. In addition to biasing the trial’s outcomes, study attrition usually necessitates that more participants be enrolled to attain adequate power for the trial results to be valid, which may increase the trial’s cost or duration or delay important results. Although attrition is likely to occur in most clinical trials, bias can be expected when the attrition rate exceeds 20% ( Marcellus, 2004 ).

Several factors can deleteriously affect participant retention. In the sections that follow, we highlight some study facets that may affect retention and suggest alternative strategies.

Study Design

A large number of follow-up tests or a study design in which participants are relegated to a control group that receives no perceived benefit may increase the likelihood of attrition. For example, some participants have withdrawn from our studies following the intervention phase because they are no longer provided with therapies after this point, although study visits continue to occur. It has been suggested that compensation in the form of monetary payments, gifts, or free health or child care could be provided to participants who attend selected study visits (e.g., Cooley et al., 2003 ). It is difficult, however, to ascertain how to gauge compensation so that it is sufficiently high to encourage participation without being so high that it is coercive. Moreover, the impact of monetary compensation on preventing attrition is not well established ( Corrigan & Salzer, 2003 ; Orrell-Valente, Pinderhughes, Valente, & Laird, 1999 ). As an alternative to participant remuneration, we have used an active control condition in many of our neurorehabilitation trials. This alternative provides participants with the potential to derive perceived benefit from study participation, even if they are not in the experimental condition, and allows investigators to compare the efficacy of the experimental intervention against a typical care strategy.

Visit Reminders

Recorded messages or telephone calls have become a common method for physician offices to remind clients of an impending appointment. The study team can likewise use these methods to remind participants of an impending study visit and to troubleshoot barriers to matriculation. With the increasing use of cellular telephones, the ability to send text message reminders to participants about study visits is also promising. Whether sent by telephone, text message, or e-mail, the content of reminders should be approved by the IRB and can be made consistent from participant to participant to ensure that no bias is introduced.

Up-Front Scheduling

Participants may not attend a scheduled study session because they forget about the session or do not have a tangible reminder of the visit. In addition to telephone or e-mail visit reminders, we provide the participant and care partner with a written document detailing the dates and times of every testing and therapy visit. The names, locations, and contact information of the person whom participants will encounter during each visit are also included. We have found that providing this information at one of the first meetings after consent induces the participants to “burn it” into their schedules and provides a concrete reminder of their study appointments.

Demographic and Other Factors

A variety of demographic factors appear to be predictive of attrition, including older age, male gender, lower education, functional impairment, poorer cognitive performance, lower verbal intelligence, and greater comorbidities or worse physical health ( Driscoll, Killian, Johnson, Silverstein, & Deeb, 2009 ). Transparency of the informed consent document; a strong relationship among the study coordinator, care providers, and participants; and consistency in protocols for maintaining contact with participants contribute to decreased attrition ( Bedlack & Cudkowicz, 2009 ). In our laboratory, we have one person who acts as participants’ primary contact for the study; however, we also cross-train all of our personnel to be knowledgeable about all of our ongoing trials so that everyone can ably respond to a participant’s needs.

Blinding in Clinical Trials

Blinding is necessary for control of bias in clinical trials. We define blinding as the process of concealing research design elements such as group assignment, treatment agent, and research hypotheses from participants, health care providers, or data collectors ( Penson & Wei, 2006 ; Portney & Watkins, 2000 ). Blinding allows the researcher to minimize threats to internal validity and construct validity, thereby strengthening external validity and improving the generalizability of results ( Portney & Watkins, 2000 ).

The importance of blinding falls along a relative continuum that the investigator must consider when designing experimental research. When treatment and control group interventions are indistinguishable, such as in pharmaceutical trials, blinding of personnel is relatively less important and easier to achieve. When treatment and control group interventions are dissimilar, however, such as in behavioral trials, blinding becomes relatively more important and harder to achieve. The variety of practice settings and intervention strategies rehabilitation professionals use necessitates a mastery of blinding techniques across this continuum.

Whom Are We Blinding?

For the purposes of this article, we adopt the language used in the Consolidated Standards of Reporting Trials (CONSORT) statement ( Schulz, Altman, & Moher, 2010 ):

• Participants should be blinded to group assignment to control for the psychological effects associated with knowing group assignment. Participant knowledge of group assignment may bias the study in terms of altered attitudes, compliance, cooperation, and attendance ( Pocock, 1983 ).
• Health care providers are the people administering the intervention to participants or are professionals otherwise involved in the care of participants during the trial. Blinding of health care providers is especially important when knowledge of group assignment may affect normal care treatment decisions, cause a provider to monitor changes more closely, or result in increased excitement or enthusiasm ( Pocock, 1983 ).
• Data collectors may administer outcome assessments, score assessments, analyze the data, and manage databases. Blinding of the data collector to group assignment is necessary to ensure objectivity and avoid the risk that assessors will record more favorable responses when treatment status is known or may assume that improved performance is evidence of treatment status ( Pocock, 1983 ). Blinding of data collectors is also important in behavioral trials because of the influence of clinical judgment on outcome assessments.

Strategies for achieving successful blinding with these groups are described in the sections that follow.

Types of Blinding

The terms unblinded, single-blinded, double-blinded , and triple-blinded have been used to describe a variety of design methodologies ( Friedberg, Lipsitz, & Natarajan, 2010 ; Iber, Riley, & Murray, 1987 ; Meinert & Tonascia, 1986 ; Penson & Wei, 2006 ; Portney & Watkins, 2000 ). Unblinded studies are those in which all parties are aware of group assignment. They are relatively simple to carry out and allow health care providers to make informed treatment decisions. Unblinded trials are limited by an increased likelihood of bias, participant dissatisfaction with nontreatment status, dropouts, and preconceived notions about treatment ( Friedman, Furberg, & DeMets, 1998 ).

The term single - blind is often used in two distinct ways. First, single-blind may be used to describe a trial in which only the investigator is aware of group assignment ( Friedman et al., 1998 ). Such usage is common in pharmaceutical trials, in which it is relatively easy to blind the participant. In the health and rehabilitation sciences, however, the term single - blind refers to trials in which the data collector is blind to group assignment. The advantages and disadvantages of the single-blinded study are similar to those of an unblinded study.

Double-blind is the most commonly used term to describe trials in which neither the participant nor the investigator is aware of group assignment. Having evolved within the realm of pharmaceutical trials, this level of blinding can be difficult to achieve in behavioral research because practitioners are not easily deceived by bogus interventions. Double-blinded trials reduce the risk of bias because the actions of the investigator theoretically affect both the treatment and the control group equally. The term triple-blind is sometimes used interchangeably with double-blind . Accordingly, a degree of ambiguity exists in the usage of these terms. To address this inconsistency, the CONSORT statement suggests that authors “explicitly report the blinding status” of the individuals or groups involved in the trial ( Moher et al., 2010 , p. 12).

Strategies for Blinding

Many methods are available for successfully blinding participants, health care providers, and data collectors in pharmaceutical trials, in which use of a treatment allocation scheme, established masking guidelines, a data scheme, coding of drugs, and placebos and development of rapid unblinding protocols all make the blinding process relatively easy ( Friedman et al., 1998 ; Meinert & Tonascia, 1986 ; Penson & Wei, 2006 ; Pocock, 1983 ). The application of these strategies to behavioral research is often impossible, impractical, or infeasible, thus making blinding more difficult. Yet, investigators have developed a number of novel approaches for blinding key groups throughout the research process. Table 2 presents strategies for blinding these key groups.

Strategies for Blinding Key Players in Behavioral Trials

Blinding Participants.

One strategy for blinding participants is to keep publicly available documents general in nature—for example, by keeping hypotheses out of recruitment literature and consent documents. Blinding is also strengthened when participants are unaware of the research design and when active control participants are used. Participants should be directed to not discuss group assignment with health care providers and data collectors ( Lowe, Wilson, Sackley, & Barker, 2011 ). For example, in our laboratory, we fully describe the nature of the interventions that participants may receive; however, we refrain from using language in our consents or advertisements that may suggest to participants which group is the experimental group or which condition is expected to respond better to the intervention.

Blinding Health Care Providers.

Blinding health care providers presents a unique challenge within the helping professions. Therapists are not easily fooled by sham interventions. They know which interventions are legitimate and which are not. To limit bias, health care providers may be blinded to hypotheses, eligibility criteria, and outcome measures. Therapeutic interventions should be manualized so that they are provided in a consistent manner ( Johnson & Remien, 2003 ). Fidelity measures may be developed and deployed to ensure that interventions are consistent. Training and supervision of health care providers helps control for variability in the delivery of interventions ( Johnson & Remien, 2003 ). For example, in our laboratory, we provide regular in-services to our treating therapists that include a review of the pertinent literature, case studies and videos of the interventions and common treatment responses, and other training strategies to familiarize therapists with the protocol. Additionally, we standardize the therapy regimen in our manual of procedures and conduct regular checks to ensure that therapies are being administered consistently.

Blinding Data Collectors.

To limit bias, the data collector and health care provider groups should be composed of different sets of practitioners. The use of objective outcome measures with established reliability and validity also helps minimize threats of bias ( Penson & Wei, 2006 ). Data collectors should be blinded to hypotheses, group assignment, purpose, and the interventions received by the participants they assess. Qualitative strategies, such as use of a diary, help document any irregularities during data collection. Additionally, data collectors should have no access to study data, including databases, previously completed assessments, notes, or questionnaires ( Lowe et al., 2011 ). Data collectors should be kept away from health care providers whenever possible. If it is not possible to keep these groups away from each other, then study-related business should not be discussed in common areas and incoming telephone calls should be screened so that data collectors do not hear discussion regarding intervention ( Lowe et al., 2011 ).

Blinding Other Personnel.

Other study-related personnel sometimes require blinding. Whenever possible, the PI should limit interactions with participants, health care providers, and data collectors. We acknowledge that the PI must balance the need to limit bias with the logistical considerations of managing the study. We suggest that PIs engage in a process of epoche to document their interactions. Blinding of physicians involved in ordinary care may be required under certain circumstances. When it is not possible to blind the physicians, it is helpful to schedule study-related appointments after medical visits so that participant reports of study-related activities will not affect standard medical care. Blinding of data analysts is arguably easiest to achieve. Blinding of analysts allows for handling of data and statistical issues in an objective manner ( Polit, 2011 ). The best ways to achieve blinding of analysts is to employ an independent statistician, recruit a collaborator who is blinded to group assignment, or withhold the blinding codes from the analysis group until analysis is completed. When it is not possible to employ a statistician, it is best for the PI to enlist a confederate who is responsible for developing the coding scheme, recording and entering data, and withholding the coding key from the PI until the analysis is complete ( Polit, 2011 ).

As EBP continues to be emphasized, occupational therapists must become adept in the deployment and consumption of information from clinical trials. This level of proficiency is important given that evidence is increasingly a prerequisite for reimbursement of services. As a first step, this article presents potential barriers and alternative strategies associated with three of the most vexing aspects of conducting clinical trials: recruitment and retention of participants and blinding. Investigators should keep the following points in mind:

• Development and implementation of the recruiting plan start before the study begins.
• Successful recruiting plans incorporate both active and passive recruiting strategies.
• Participant retention can be maximized through the use of designs with active controls, technology-supported visit reminders, and up-front scheduling.
• Participants, health care providers, and data collectors should be blinded when possible.
• Concealing design elements from key players helps minimize threats of bias.

Use of these strategies will help increase the success of clinical trials research in the health and rehabilitation sciences.

Contributor Information

Stephen J. Page, Stephen J. Page, PhD, MS, MOT, OTR/L, FAHA, is Associate Professor and Director, Neuromotor Recovery and Rehabilitation Laboratory (the “Rehablab” ® ), Division of Occupational Therapy, Ohio State University Medical Center, 453 West Tenth Avenue, Suite 416, Columbus, OH 43210; [email protected] .

Andrew C. Persch, Andrew C. Persch, MS, OTR/L, is Graduate Assistant, Division of Occupational Therapy, School of Health and Rehabilitation Sciences, and Graduate Student, Doctor of Philosophy in Health and Rehabilitation Sciences, Ohio State University Medical Center, Columbus.

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Open Access

Study Protocol

Protocol for Cerebellar Stimulation for Aphasia Rehabilitation (CeSAR): A randomized, double-blind, sham-controlled trial

Roles Project administration, Writing – original draft, Writing – review & editing

Affiliation Department of Physical Medicine and Rehabilitation, School of Medicine, Johns Hopkins University, Baltimore, MD, United States of America

Roles Project administration, Writing – review & editing

Current address: Independent Researcher, Salt Lake City, UT, United States of America

Current address: School of Medicine, New York Medical College, Valhalla, NY, United States of America

Roles Methodology, Writing – review & editing

Affiliation Johns Hopkins Biostatistics Center, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, United States of America

Roles Conceptualization, Methodology, Writing – review & editing

Affiliations Department of Physical Medicine and Rehabilitation, School of Medicine, Johns Hopkins University, Baltimore, MD, United States of America, Department of Neurology, School of Medicine, Johns Hopkins University, Baltimore, MD, United States of America, Department of Cognitive Science, Krieger School of Arts and Sciences, Johns Hopkins University, Baltimore, MD, United States of America

Roles Conceptualization, Funding acquisition, Methodology, Supervision, Writing – review & editing

* E-mail: [email protected]

• Becky Lammers, 
• Myra J. Sydnor, 
• Sarah Cust, 
• Ji Hyun Kim, 
• Gayane Yenokyan, 
• Argye E. Hillis, 
• Rajani Sebastian

• Published: August 26, 2024
• https://doi.org/10.1371/journal.pone.0298991
• Reader Comments

In this randomized, double-blind, sham-controlled trial of Cerebellar Stimulation for Aphasia Rehabilitation (CeSAR), we will determine the effectiveness of cathodal tDCS (transcranial direct current stimulation) to the right cerebellum for the treatment of chronic aphasia (>6 months post stroke). We will test the hypothesis that cerebellar tDCS in combination with an evidenced-based anomia treatment (semantic feature analysis, SFA) will be associated with greater improvement in naming untrained pictures (as measured by the change in Philadelphia Picture Naming Test), 1-week post-treatment, compared to sham plus SFA. We will also evaluate the effects of cerebellar tDCS on naming trained items as well as the effects on functional communication, content, efficiency, and word-retrieval of picture description, and quality of life. Finally, we will identify imaging and linguistic biomarkers to determine the characteristics of stroke patients that benefit from cerebellar tDCS and SFA treatment. We expect to enroll 60 participants over five years. Participants will receive 15, 25-minute sessions of cerebellar tDCS (3–5 sessions per week) or sham tDCS combined with 1 hour of SFA treatment. Participants will be evaluated prior to the start of treatment, one-week post-treatment, 1-, 3-, and 6-months post-treatment on primary and secondary outcome variables. The long-term aim of this study is to provide the basis for a Phase III randomized controlled trial of cerebellar tDCS vs sham with concurrent language therapy for treatment of chronic aphasia.

Trial registration: The trial is registered with ClinicalTrials.gov NCT05093673 .

Citation: Lammers B, Sydnor MJ, Cust S, Kim JH, Yenokyan G, Hillis AE, et al. (2024) Protocol for Cerebellar Stimulation for Aphasia Rehabilitation (CeSAR): A randomized, double-blind, sham-controlled trial. PLoS ONE 19(8): e0298991. https://doi.org/10.1371/journal.pone.0298991

Editor: Dinesh V. Jillella, Emory University, UNITED STATES OF AMERICA

Received: February 23, 2024; Accepted: July 9, 2024; Published: August 26, 2024

Copyright: © 2024 Lammers et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: No datasets were generated or analysed during the current study. All relevant data from this study will be made available upon study completion.

Funding: The trial is fully funded by the National Institute on Deafness and Other Communication Disorders (NIH/NIDCD) R56/R01 DC019639. The funders had and will not have a role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. This funding source had no role in the design of this study and will not have any role during its execution, analyses, interpretation of the data, or decision to submit results.

Competing interests: The authors have declared that no competing interests exist.

Introduction

Aphasia is a devastating outcome and one of the leading causes of disability following stroke. Aphasia adds substantial costs to the acute [ 1 ] and chronic [ 2 ] care of individuals with stroke and is an independent predictor of subsequent functional dependence and death [ 3 ]. Anomia or difficulty with naming is the most common deficit in individuals with aphasia. Currently, the most widespread rehabilitation approach for aphasia is speech and language therapy (SALT) [ 4 ]. Although the interventions to improve naming can have benefits [ 5 – 9 ], a substantial number of treatment sessions is usually required to show gains, particularly in individuals with chronic large left hemisphere stroke. Therefore, to address how the treatment of aphasia might be made more effective, researchers are now using an emerging, safe, non-painful, and low-cost brain stimulation method called transcranial direct current stimulation (tDCS) [ 10 ]. There is evidence that tDCS may be useful for enhancing the effects of behavioral aphasia treatment. Evidence is growing that the add-on use of tDCS can aid in the recovery of aphasia as highlighted by international recommendations [ 11 ]. However, there is a general lack of consensus regarding the optimal electrode montage for stimulation in post-stroke aphasia. Addressing this barrier is critical for successful clinical translation.

Stimulating the residual left hemisphere region is the most common approach based on the observation that optimal recovery involves the functional re-recruitment of the remaining left-hemisphere tissue [ 12 – 16 ]. However, encephalomalacia filled with cerebrospinal fluid at the site of stroke affects the electrical current flow, reducing the exposure of the targeted perilesional tissue to stimulation [ 17 ]. This issue makes selection of optimal electrode locations in the left hemisphere difficult. Approaches to address this issue involve advanced electrical field modeling methods [ 18 – 20 ] or individualized electrode placement based on pre-treatment functional magnetic resonance imaging (fMRI) scans so that stimulation targets residual functional tissue [ 21 – 24 ]. However, advanced electrical field modeling and fMRI are cost-intensive and require substantial technological expertise. This would limit the incorporation of tDCS into routine speech language pathology clinical practice. We propose a novel approach to augment aphasia treatment by stimulating the right cerebellum. The right cerebellum is not only involved in cognitive and language functions (see [ 25 – 27 ] for reviews) but is also distant enough from typical stroke locations associated with aphasia that electrical current flow patterns are unlikely to be affected by the encephalomalacia [ 17 ]. In addition, this approach is suitable for patients who have large left hemisphere strokes and aphasia associated with bilateral hemispheric strokes.

In 2017, our group published the first study showing that cerebellar tDCS has the potential to augment aphasia treatment in a participant with bilateral middle cerebral artery infarct resulting in aphasia [ 28 ]. Subsequently, another group, utilizing a crossover study design, showed that 5 sessions of cathodal cerebellar tDCS coupled with language treatment improved verb generation immediately post-treatment in chronic post-stroke aphasia [ 29 ]. In a follow up study, we conducted a randomized, double-blind, sham controlled, within-subject crossover study in 24 chronic stroke participants with aphasia [ 30 ]. We also investigated whether there are any differences in anodal versus cathodal cerebellar tDCS on naming performance as prior studies in healthy controls have shown beneficial language effects for anodal and cathodal cerebellar stimulation [ 17 , 31 – 33 ]. Participants received 15 sessions of anodal (n = 12) or cathodal (n = 12) cerebellar tDCS + computerized aphasia therapy in Phase 1 followed by sham + computerized aphasia therapy in Phase 2, or the opposite order. The results of our study revealed several important findings, which have significant implications for the proposed study. First, we found that cerebellar tDCS significantly improved naming in trained (Naming 80) and untrained (Philadelphia Naming Test, PNT [ 34 ]) items immediately post-treatment, and the significant improvement in untrained naming was maintained at two months post-treatment. Second, we found that participants receiving cathodal stimulation showed significantly greater gains (compared to sham) in naming than participants receiving anodal stimulation, indicating that cathodal stimulation might be more favorable than anodal stimulation to augment aphasia treatment. Thus, these results indicate that cathodal cerebellar tDCS combined with language treatment has the potential to augment aphasia treatment.

tDCS is believed to enhance neural plasticity by temporarily modulating resting membrane potentials of neurons in targeted areas [ 35 , 36 ]. Anodal stimulation may lead to depolarization of the neuronal membranes resulting in greater excitability, whereas cathodal stimulation may lead to hyperpolarization resulting in lower excitability. Because the cerebellar cortex is highly convoluted and the neuronal architecture is different from cortical circuits, the polarity of cerebellar tDCS effects is not necessarily the same as the polarity of cortical tDCS effects. Animal and human studies indicate that cerebellar tDCS is most likely to produce its effects by polarizing Purkinje cells ‐ the inhibitory output neurons of the cerebellar cortex ‐ and thereby changing the levels/pattern of activity in the deep cerebellar output nuclei, which are the efferent targets of the Purkinje cells [ 37 , 38 ]. Critically, one of the deep cerebellar nuclei, the dentate nucleus, has a disynaptic excitatory connection through the thalamus to the cortical language areas. Based on this known circuitry, we hypothesize that a single session of right cathodal cerebellar stimulation will result in transient depression of Purkinje cell activity, thereby reducing the inhibitory signals that the cerebellum sends to the cortical language areas. Anodal cerebellar stimulation will exert the opposite effect, i.e., it will increase the discharge from the Purkinje cells, thereby increasing the inhibitory signals the cerebellum sends to the cortical language areas. Thus, it is plausible that multiple sessions of cathodal cerebellar tDCS will provide cortical excitation, thereby facilitating the engagement of the residual left hemisphere language areas.

In this proposal, we will combine cerebellar tDCS with semantic feature analysis (SFA) treatment for post-stroke aphasia (see [ 39 – 43 ] for reviews regarding SFA). SFA is a semantically based treatment approach for naming deficits. SFA was chosen for this study for three main reasons (1) SFA has a strong potential for promoting acquisition and generalization effects for participants with anomia, (2) SFA is an effective therapy for treating naming deficits for individuals with a range of aphasia types and severities, and (3) SFA is a treatment that is frequently used by practicing speech-language pathologists (SLPs). The driving premise of SFA treatment is that when individuals generate semantic features of a target word (i.e., accessing their semantic network), they improve their ability to retrieve the target because they have strengthened access to its conceptual representation [ 41 , 44 ]. The theoretical mechanism by which SFA promotes generalization comes from the spreading activation theory [ 45 ] which posits that accessing/activating a particular lemma (or its features) results in activation of the lemmas of semantically related concepts. Prior studies provide strong compelling evidence that the right cerebellum, the target of our tDCS treatment, is a critical structure involved in semantic processing and naming [ 25 – 27 , 46 – 48 ].

Here we describe a protocol for an ongoing randomized, double-blind, sham-controlled study of cerebellar tDCS for augmenting anomia therapy in chronic aphasia. Participants are enrolled parallelly at two sites within the Johns Hopkins Rehabilitation Network: Johns Hopkins Hospital and Howard County General Hospital. We hypothesize that 15 sessions of cathodal cerebellar tDCS plus SFAwill be associated with greater improvement in naming untrained pictures (as measured by the change in Philadelphia Picture Naming Test, PNT [ 34 ], 1-week post-treatment, compared to sham plus SFA. For secondary outcomes, we hypothesize that cathodal cerebellar tDCS plus SFAwill result in greater improvement in discourse (as measured by change in total content units (CU) and syllable per CU in picture description [ 49 ] and greater improvement in functional communication skills (as measured by change in Communication Activities of Daily Living–CADL-3 [ 50 ] compared to sham plus SFA. We also hypothesize that 15 sessions of cathodal cerebellar tDCS plus SFA will result in greater improvement on the Western Aphasia Battery-Revised (WAB-R) [ 51 ], General Health Questionnaire (GHQ)-12 [ 52 ], and Stroke and Quality of Life Scale (SAQOL-39) [ 53 ] compared to sham plus SFA.

A second aim is to identify whether neural (functional and structural) biomarkers and linguistic characteristics can predict response to cerebellar stimulation and SFA treatment. Our prior work in cerebellar tDCS in aphasia has shown that individual response to tDCS treatment is highly variable. However, little is known about how factors related to imaging and linguistic characteristics combine to induce treatment responsiveness. We will carry out resting state functional magnetic resonance imaging (rsfMRI), diffusion tensor imaging (DTI), high resolution structural imaging, and detailed linguistic testing before the start of treatment to determine whether these factors can predict response to cerebellar tDCS and/or SFA. This exploratory aim may identify stroke patients who are mostly likely to benefit from cerebellar tDCS and/or SFA. This result may have significant implications for designing a Phase III randomized controlled trial.

Materials and methods

This study, Cerebellar Stimulation for Aphasia Rehabilitation (CeSAR), is a Phase II trial of cathodal cerebellar tDCS plus SFA treatmentvs. sham plus SFA treatment, evaluated in double-blind, randomized, sham-controlled design in chronic stroke. Participants with chronic aphasia are enrolled at two sites within the Johns Hopkins Rehabilitation Network at least 6 months after the onset of stroke. The two sites will be the Johns Hopkins Hospital and Howard County General Hospital. Sixty participants are expected to enroll over five years. Enrollment for this study began on October 25, 2021. The SPIRIT schedule of enrollment, interventions, and assessments is included as Fig 1 . The World Health Organization Trial Registration Data Set compiled by ClinicalTrials.gov (NCT05093673) is reproduced in Table 1 (SPIRIT Item 2b). The SPIRIT checklist is included in S1 File . A full accounting of evaluations and unabridged protocol approved by the IRB is available in S2 File (January 29, 2024) and important protocol modifications will be available from the corresponding author and by viewing the ClinicalTrials.gov study entry. A sample consent form is included in S3 File .

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Patient population-inclusion and exclusion criteria

Participants must be >6 months post ischemic or hemorrhagic left-hemisphere stroke and diagnosed with post-stroke aphasia and naming impairment using the Western Aphasia Battery-Revised (WAB-R). They must also be 18 years or older, and English-speaking by self-report with no lesions on the right cerebellum, with no previous neurological disorder other than stroke, or other neurodegenerative or psychiatric disorders. Individuals with seizures within the previous 6 months, those taking medications that lower the seizure threshold (e.g., methylphenidate) or N-methyl-D-aspartate (NMDA) antagonists (e.g., memantine), and those with a history of brain surgery or with any metal in the head will be excluded. We will also exclude those with uncorrected hearing or vision loss by self-report, those who score >80% on the Philadelphia Naming Test (PNT) at baseline, and those with severely impaired auditory comprehension and/or severely limited verbal output (lower than 2 on the Auditory Comprehension subscore on the WAB-R and/or lower than 2 on the Spontaneous Speech rating scale on the WAB-R, respectively). Individuals with severe claustrophobia, cardiac pacemakers or ferromagnetic implants, and pregnant women will be excluded from the MRI portion of the study.

Inclusion criteria.

• Chronic ischemic or hemorrhagic left hemisphere stroke
• Fluent speaker of English by self-report
• Age 18 or older
• 6 months post onset of stroke
• Diagnosis of aphasia and naming impairment using the Western Aphasia Battery-Revised

Exclusion criteria.

• Lesion in the right cerebellum
• Previous neurological disorder (other than stroke) affecting the brain, or any other neurodegenerative disorder or psychiatric disorder
• Seizures during the previous 6 months
• Uncorrected visual loss or hearing loss by self-report
• Use of medications that lower the seizure threshold (e.g., methylphenidate, amphetamine salts)
• Use of N-methyl-D-aspartate (NMDA) antagonists (e.g., memantine)
• >80% correct response on the Philadelphia Naming Testing at baseline
• History of brain surgery or any metal in the head
• Severely impaired auditory comprehension (lower than 2 on the Comprehension subscore on the Western Aphasia Battery-Revised)
• Severely limited verbal output (lower than 2 on the Spontaneous Speech rating scale on the Western Aphasia Battery-Revised)
• Individuals with severe claustrophobia, cardiac pacemakers or ferromagnetic implants, and pregnant women will be excluded from the MRI portion of the study.

Informed consent

A signed and dated informed consent form will be obtained from each participant. For participants who cannot consent for themselves, a legally authorized representative, such as a legal guardian or power of attorney, must sign the consent form. The consent form will describe the purposes, procedures, risks, and benefits of participation in the study, as well as the participant’s ability to withdraw consent at any time without retaliation or impact on clinical care. A copy will be given to each participant or legally authorized representative.

Once the consent form has been signed, participants will be assigned a temporary identification number for the purposes of initial screening.

All research staff authorized to obtain informed consent will have completed the Miami CITI course in the Responsible Conduct of Research and Protection of Human Subjects prior to their involvement with the study. Furthermore, they will be oriented to the study and trained by the study PI and study co-investigators who have all had extensive training and experience in the ethical and practical aspects of informed consent procedures.

Participant confidentiality

Participation in this study should not put participants in any legal risk, even in the case of a breach of confidentiality. We will undertake every effort to keep the information in the study confidential. Participants will be assigned a code number in order to keep protected health information confidential. Consent forms and source documents will be maintained at the PI lab in a locked cabinet. All digital data will be done using participant identification numbers only and will be stored on a password-protected and encrypted format in a manner that is Johns Hopkins IRB compliant. This will include the Clinical Research Management System (CRMS), Research Electronic Data Capture (REDCap), and Johns Hopkins Microsoft One Drive. All are web-based applications designed to organize and streamline clinical research management. CRMS is integrated with Epic, Hopkins enterprise EMR, as well as Johns Hopkins IRB. This integration improves communication among study team members, stores subject enrollment information in a secure location, assists with recruitment, and allows research results to be promptly incorporated into the EMR. Everybody involved in the study will have completed the appropriate HIPAA training and are fully aware of confidentiality issues. No names will be included in any publications resulting from this work.

Randomization

Prior to randomization, all eligible participants will receive comprehensive language and cognitive evaluations as well as MRI for those who consent and who have no contraindication. Participants will be randomly assigned 1:1 (cerebellar cathodal tDCS plus SFA treatment or sham tDCS plus SFA treatment). The randomization is stratified by study site (JHH vs Howard County), aphasia type (fluent vs. non-fluent, classified using WAB-R), and aphasia severity. Aphasia severity will be classified using WAB-R Aphasia Quotient in 4 categories (very severe aphasia: 0–25, severe aphasia: 26–50, moderate aphasia: 51–75, and mild aphasia: 76–93.8). Covariate-adaptive randomization method developed by Pocock and Simon, 1975 [ 54 ] will be implemented in REDCap. This method ensures balance on important baseline covariates by treatment arm by calculating the difference in these covariates (site, aphasia type and severity) each time a participant needs be randomized and then randomizes with high probability (80%) to the arm that corrects the imbalance on covariates.

The SLP will enter the baseline and eligibility information of a participant prior to enrollment on REDCap. If the participant’s eligibility is confirmed, then the algorithm implemented in REDCap will evaluate the treatment arm distribution in participants already randomized and then generate treatment allocation group (sham or tDCS) based on the randomization scheme. Each participant will receive a unique six-digit codes (provided by the manufacturer of the tDCS stimulator), which will instruct the stimulator to deliver either active stimulation or placebo (sham). These codes will be entered into REDCap prior to starting the study. The study coordinator will enter the codes in REDCap.

Both groups will receive semantic feature analysis treatment, a commonly used treatment for naming deficits in aphasia. It is currently unknown whether or not cerebellar tDCS augments the effect of semantic feature analysis in the chronic phase after stroke. Therefore, a sham group is justified.

The study is to be conducted in a double-blind manner. All participants, the members of the study team who administer the assessments, those who administer treatments, as well as the study biostatistician performing the statistical analyses will be blinded.

The MRI scans will be performed prior to the start of the study on a 3T Philips system at the F.M. Kirby Center at the Kennedy Krieger Institute. Imaging will be done for patients who have no MRI contraindications. Imaging will include structural and functional scans. Structural scans will include high resolution T1 and T2 weighted images, Fluid Attenuation Inversion Recovery (FLAIR) scans, and Diffusion Weighted Imaging (DWI) images. Functional scan will include resting state functional MRI.

Participants will receive 15 sessions of SFA treatment (3–5 sessions per week over the course of 3 to 5 weeks) and each session will be 60 minutes. Prior to the start of treatment, participants will be randomly assigned to receive either sham plus SFA or active tDCS plus SFA.

The SLP will start the Semantic Feature Analysis Treatment. Participants will receive SFA treatment for 60 minutes and tDCS for the first 25 minutes. SFA treatment employed in this study will include 50 items and their relevant features from eight semantic categories. Items included in each participant’s treatment list will be determined based on performance on a picture-naming task. The naming task will consist of 200 items across eight semantic categories (food [fruits, vegetables], animals, transportation, clothing, furniture, music, sports, toys). The naming task will be administered once. To qualify for treatment, an item must be named incorrectly. To avoid effects of repeated exposure, items included on the naming task will be constrained such that they do not occur in the primary outcome variable (PNT).

Therapy tasks will be administered through a computer with clinician assistance using Microsoft PowerPoint. Participants will be trained on 7–12 items per session depending on each participant’s aphasia severity. The treatment protocol will be adapted from Doyle, Dickey and colleagues [ 55 , 56 ]. The treatment will proceed according to a series of steps including naming aloud the target picture, generating semantic features, naming aloud the target picture again, and generating a sentence using the target word. Participants will be asked to generate semantic features for each target picture in five categories: group [superordinate category], function [use/action], description [physical properties], context [location], and other/personal [association]. A three-level cueing hierarchy will be used to elicit features, consisting of general prompt (e.g., “How would you describe this?”), followed by a relevant directed question (e.g., “What does this feel like?”) and a binary forced-choice question (e.g., “Is this item smooth or rough?”).

tDCS will be delivered for 25 minutes using the Soterix Medical 1x1 Clinical trials device. Soterix 1×1 CT is the most advanced and customizable system for true double-blind control trials. Consistent with other studies on cerebellar tDCS [ 28 – 30 , 57 ], the current study will utilize 2 mA of cathodal tDCS stimulation generated between two 5 cm x 5 cm saline-soaked sponges. The active electrode (cathode) will be placed on the right cerebellar cortex, 1 cm under and 4 cm lateral to the inion (approximately comparable to the projection of cerebellar lobule VII onto the scalp [ 31 ]. The reference electrode (anode) will be placed over the right shoulder. For both tDCS and sham interventions, current will be ramped up over a 15 second interval at stimulation onset, eliciting a transient tingling sensation that effectively blinds the participant to treatment condition [ 58 ]. After the ramp up, in the sham condition, current intensity will be ramped down over a 15 second interval to 0 mA. Participants will rate their pain levels at the beginning and end of stimulation with the Wong-Baker FACES Pain Rating Scale (wongbakerfaces.org) [ 59 ]. In each session, participants will be asked to inform the SLP about any side effects. Participants generally tolerate tDCS well, the main reported side effects being initial tingling or itching sensations at the beginning of the session for some participants [ 60 ]. Stimulation (for both tDCS and sham conditions) will start at the same time as the aphasia treatment. Aphasia treatment will continue for another 35 minutes after the completion of 25 minutes of real tDCS or sham tDCS for a total of 60 minutes per session.

Intervention for a participant will be discontinued if any of the following criteria are met: Participants will be removed from the study if they are unable to comply with task instructions or tolerate the tDCS procedure.

When the study ends, participants will continue to receive management with Dr. Argye Hillis (study neurologist) or their own neurologist as usual (generally follow-up visits approximately every 12 months). If a patient’s participation in the study ends prematurely s/he will still receive care as before. In sum, termination of the study or termination of participation in it will not affect regular therapy he or she may be receiving.

Primary outcome

The primary outcome will be defined as the change in accuracy of naming untrained pictures measured by the Philadelphia Naming Test (PNT), one week after the end of semantic feature analysis (SFA). Although our previous study [ 30 ] showed that the significant improvement in untrained naming (PNT) with cathodal cerebellar tDCS was maintained at two months post-treatment, we choose to measure untrained naming one week post-treatment in the current study because we are using a different study design and naming treatment.

Secondary outcomes

In addition to the primary outcome, several secondary analyses will be conducted.

• Trained Picture Naming. We will assess if tDCS has an effect on naming items trained during treatment (trained picture naming). In addition to assessing changes in correct naming, we will also evaluate treatment-related changes in naming errors to provide additional insight into naming recovery following cerebellar tDCS. Naming errors will be categorized as 1) semantic paraphasias; 2) phonological paraphasias; 3) mixed (phonological and semantic) paraphasias; 4) non-responses; and 5) unrelated responses.
• Discourse. We will assess change in discourse abilities, as measured by the change in the total Content Units (CU) and syllable per CU produced by the participants during connected speech. Participants will be required to describe the Cookie Theft Picture from the Boston Diagnostic Aphasia Examination.
• Functional Communication Skills. We will also measure changes in everyday functional communication skills assessed with the Communication Activities of Daily Living, third edition (CADL-3).
• Finally, we will administer 3 tests from the Research Outcome Measurement in Aphasia-Core Outcome Set (ROMA-COS). The WAB-R will be administered as a part of the baseline testing. We will also assess changes in emotional wellbeing (measured by General Health Questionnaire (GHQ)-12 and quality of life (measured by Stroke and Aphasia Quality of Life Scale (SAQOL-39).

All outcome variables (primary and secondary) will be administered at baseline (pre-treatment), 1 week, one month, three months, and six months after the completion of the treatment.

Data collection and quality assurance

All research staff authorized to obtain informed consent will have completed the Johns Hopkins University School of Medicine’s required training in the Responsible Conduct of Research and Protection of Human Subjects prior to their involvement with the study. Furthermore, they will be oriented to the study and trained by the study PI and study co-investigators who have all had extensive training and experience in the ethical and practical aspects of informed consent procedures.

The PI as well as the SLPs who administer baseline testing, treatments, and follow-up testing will be blinded to participant treatment assignments (described in full in the protocol provided in the S2 File ). Participants will be assigned a code number in order to keep protected health information confidential. Consent forms and source documents will be maintained at the PI lab in a locked cabinet. All digital data will be done using participant identification numbers only and will be stored on a password-protected and encrypted format in a manner that is Johns Hopkins IRB compliant.

The PI (an ASHA certified SLP) will provide training to the two ASHA certified SLPs for scoring and administration of the assessment materials as well as the SFA treatment protocol. To ensure quality control, all assessment sessions and part of the treatment sessions will be videotaped. The PI will create a written protocol for clinicians regarding assessment and scoring, and to ensure consistency of delivery and adherence to SFA treatment protocol. This will reduce clinician-to-clinician variability, clinician drift, and contamination.

With respect to language assessment, the PI will be present for the first few assessment sessions to assure fidelity during assessment. This will be followed by regular monitoring to ensure adherence to assessment administration procedures. All deviations will be reviewed and clarified with the clinician to ensure that adherence is improved in subsequent sessions. Each clinician will have 20% of their total assessment sessions monitored quarterly for accurate implementation.

With respect to SFA treatment, the PI will be present for the initial few sessions to assure fidelity during treatment implementation. Following this, treatment fidelity will be monitored on a weekly basis by a member of the study team who is not providing treatment by reviewing short video-recorded segments of treatment for adherence to the SFA protocol using a Treatment Fidelity Checklist. All deviations will be reviewed and clarified with the treating clinician to ensure that adherence is improved in subsequent sessions. When session monitoring detects < 1 deviation across three consecutive samples, sessions will be monitored once bi-weekly for the remainder of the 3–5-week (3–5 sessions per week) treatment period. If session monitoring detects >1 deviations across three consecutive samples, sessions will be monitored daily until deviation is less than one. The PI and research team members meet weekly (or more often) to discuss questions about and implementation of the protocol.

To minimize the need for research-only in-person visits, telemedicine visits will be substituted for portions of clinical trial visits where determined to be appropriate and where determined by the investigator not to increase the participants risks. For the current study, we will utilize telemedicine visits when appropriate for consenting and for all the assessments visits (visits 1–3, 20–23). Prior to initiating telemedicine for study visits the study team will explain to the participant what a telemedicine visit entails and confirm that the study participant is in agreement and able to proceed with this method. Telemedicine acknowledgement will be obtained in accordance with the Guidance for Use of Telemedicine in Research. In the event telemedicine is not deemed feasible, the study visit will proceed as an in-person visit. Telemedicine visits will be conducted using HIPAA compliant method approved by the Johns Hopkins Health System and within licensing restrictions. Similar to in-person visits, assessment fidelity as well as regular monitoring will be conducted for telemedicine visits to ensure adherence to assessment administration procedures.

Sample size estimates

Sample size was determined based on the PI’s prior crossover trial data [ 30 ]. That data was used to estimate the variability of untrained naming score. Enrolling 52 participants (26 per group) will give us 80% statistical power to detect 0.7 SD difference in change in accuracy of naming untrained items at 1-week post-treatment between the study arms. This was done using Wald test for group assignment coefficient in linear regression at 0.1 level of statistical significance. The effect size (0.7SD) is a bit conservative compared to the difference observed on group comparison for 21 participants (10 in tDCS and 11 in sham) in the crossover trial data, when the tDCS was administered in Phase 1. We propose to enroll 60 participants to account for 10% attrition. However, if we have trouble meeting recruitment/retention goals, we will add Johns Hopkins Bayview Medical Center as a site.

Statistical analyses

The primary outcome variable will be change in accuracy of naming untrained items as measured by the PNT within 1 week after semantic feature analysis ends. The analyses will follow the Intention-to-treat (ITT) principle where participants are analyzed based on the group to which they are randomized regardless of early termination, missing data or errors in randomization detected post hoc. The primary hypothesis is H 0 : mu 1 = mu 2 versus H A : mu 1 ≠ mu 2 , where mu 1 is the mean change in accuracy of naming untrained items between baseline and 1-week post- semantic feature analysis in the tDCS group and mu 2 is the mean change in accuracy of naming untrained items between baseline and 1 week post semantic feature analysis in the sham group. Average Treatment Effect (ATE) will be estimated using linear regression model with change in accuracy of naming untrained items at 1 week as the dependent variable and group assignment (real tDCS versus sham) as the independent variable. ATE is estimated by the coefficient for the group assignment. The analysis will adjust for the covariates included in the stratified randomization.

As a secondary analysis, we will consider non-parametric mixed models for analyses of functional response over time. In particular, let Y ijk = u ik + fk(j) + e ij where Y ij is the the outcome for subject i on occasion j (0, 1, 3, 6) within treatment arm k. (Thus, both i and k are necessary to identify a subject). No covariates are necessary because of the randomization. f k (j) is a functional model we will estimate using quadratic regression splines with knot points at each of the time points. Given there are so few time points, we will not penalize the spline fit. A non-parametric estimate of a treatment effect is given by f 2 –f 1, which can show time-specific treatment effects when evaluated at specific points j. This will also demonstrate the rate (when and if) at which tDCS effects ebb. An overall effect can be estimated by simply taking the integral of f 2 –f 1 (i.e. the functional averaged effect over time). A null hypothesis of zero represents no time averaged effect of the treatment. Given that we will use regression splines, every estimator reduces to standard contrasts of regression parameters, and thus can be implemented in any statistical software package. Statistical analysis of secondary outcome variables will follow a similar approach as the primary outcome variable.

An additional goal of this project is to identify whether neural (functional and structural) biomarkers and linguistic characteristics can predict response to cerebellar stimulation and SFA treatment. This analysis considers moderation of treatment effects by pre-treatment baseline characteristics. The pre-treatment baseline characteristics include the following: Imaging: Structural (lesion volume, site, FA, MD), Functional (Fisher transformed connectivity values ( z scores); Linguistic: (Aphasia Severity score as assessed by WAB-R, Naming severity score assessed by PNT). As in Hypothesis 1, we will consider both a conservative approach, using standard contrasts and median splits on the moderating variables as well as a mixed model functional approach. We will proceed in this order:

• T-test comparing the treatment effect across median splits of the moderating variables performed separately, one at a time.
• One that assumes linearity
• One that assumes non-parametric functions

Data monitoring body

The DSMB consists of scientists in Neurology and Public Health and will monitor safety at least semi-annually and decide if the study should continue or be terminated early. DSMB members include Kyrana Tsapkini, PhD (School of Medicine, Johns Hopkins University), John W. Krakauer, MD (School of Medicine, Johns Hopkins University), and Constantine Frangakis, PhD (Bloomberg School of Public Health, Johns Hopkins University). The study SLP in consultation with the study biostatistician will generate reports semi-annually or more frequently, as determined by the DSMB, which provide statistics on enrollment, participant status, safety data, and data quality information.

Specification of safety parameters

The participant may stop testing or the intervention at any time. tDCS provides a non-invasive method to stimulate the cortex and cerebellum and modulate cortical/cerebellar activity via continuous, weak polarizing electrical current. This study will use the Soterix Medical 1X1 Clinical Trials system to administer tDCS. The Soterix transcranial Direct Current Stimulator Clinical Trials (1x1-CT) system is the most advanced and customizable stimulation for true double-blind control trials. It is powered by four 9-V batteries with an output of 1–2.5 milliamperes (mA). Anodal tDCS (A-tDCS) results in an increase in cortical excitability. Cathodal tDCS results in decrease in cortical excitability. To date, no serious adverse effects of tDCS have been reported in the literature as long as safety guidelines are followed [ 11 , 61 ]. A recent review updated and consolidated the evidence on the safety of tDCS [ 60 ]. This review shows that the use of conventional tDCS protocols in human trials (≤40 min, ≤4 mA) has not produced any reports of a serious adverse effect or irreversible injury across over 33,200 sessions and 1000 subjects with repeated sessions. This includes a wide variety of subjects, including participants with stroke. Very minor side effects such as itching, tingling, burning have been reported, as well as temporary headache, sleepiness, dizziness. However, they were generally indistinguishable from those reported by participants receiving sham stimulation. The current study will only administer 2 mA for 25 minutes per treatment session. It is important to note that tDCS does not cause significant heating effects under the electrodes, alter the blood-brain barrier, or induce edema.

Our recent study in chronic post stroke aphasia (20 min, 2mA) in 24 participants did not produce any negative effects associated with tDCS administration beyond mild itching/tingling at the beginning of the treatment session [ 30 ]. A recent large crossover trial in 36 participants with Primary Progressive Aphasia (20 min, 2mA) reported no episodes of intolerability and no serious adverse effects [ 62 ]. On the Wong-Baker FACES Pain Rating Scale, the mean pain rating for tDCS was 2.21 (standard deviation 2.48, range 0–10) and the mean rating for sham was 2.14 (standard deviation 2.13, range 0–10).

Another large, randomized control trial in 74 participants with aphasia reported 8 mild, non-serious adverse events and there were no statistically significant differences between treatment groups for number of adverse events [ 21 ]. 2 participants (6%) in the active tDCS group experienced transient scalp redness/irritation (erythema) compared with none in the sham tDCS group. On the Wong-Baker FACES Pain Rating Scale, most often individuals reported no hurt: 94% (n  =  476) in the active tDCS group vs 86% (n  =  511) in the sham group. The highest pain rating reported was 3 (indicating “hurts even more”), which was reported 4 times by 2 individuals (3%), both in the sham group. Taken together, all available research suggests that prolonged application should not pose a risk of brain damage when applied according to safety guidelines.

Participants may undergo MRI scanning in the present study. The effects of undergoing MR scanning have been extensively studied and there are no risks associated with an MR exam. The patient may, however, be bothered by feelings of confinement (claustrophobia), and by the noise made by the magnet during the procedure. They will be asked to wear earplugs or earphones while in the magnet.

All MRI scans will be reviewed by co-investigator and board-certified neurologist (Dr. Argye Hillis) and any suspicious abnormalities will be referred to a board-certified neuroradiologist. Please note that all of our participants, who will be recruited from the outpatient or stroke clinic, who do not have contraindication for MRI will have had a clinical MRI post-stroke. If unexpected abnormalities ‐ incidental findings ‐ are seen (which is unlikely, as every patient will have had a clinical MRI as part of their evaluation for stroke), the participant will be asked permission to contact the primary care physician about the abnormality and will be offered a timely appointment with a neurologist (Dt. Argye Hillis, co-investigator) if appropriate.

Participants will be carefully screened over the phone prior to being scheduled, to assure that they meet study criteria. tDCS stimulation will be ramped up over the first 15 seconds of stimulation in order to eliminate the sensation of tingling that can occur under the electrodes during the initial moments of tDCS application. The participant may stop testing or the intervention any time. There will be emergency personnel and equipment on hand for safety.

Adverse events will be monitored during the entire visit by the study team. The families will be given telephone numbers of the study team as well. The study physician (Dr. Argye Hillis) and the DSMB will be notified immediately if any adverse events are reported. If a significant safety concern arises, participants may be unblinded in order to address it. The DSMB will determine if the adverse event is a serious adverse event. Adverse events will be monitored until they are resolved or clearly determined to be due to a subject’s stable or chronic condition or intercurrent illness. In the case of any unexpected adverse events involving risks to participants or others that are related/possibly related to the research, a Protocol Event Report will be prepared by the Study Coordinator, the PI will be informed immediately, and the IRB will be contacted within 10 days as per Johns Hopkins Medicine IRB policy; deaths will be reported within 72 hours. Also, as required by IRB policy, any unexpected adverse device effects, potential breaches of confidentiality, unresolved participant complaints will be promptly reported to the IRB. Any other adverse events that do not require prompt reporting will be summarized and reported to the IRB at the time of continuing review.

Summary and concluding remarks

It is our hope that completion of this project will result in better understanding of whether and how cerebellar tDCS coupled with behavioral therapy may help individuals with post stroke aphasia. The cerebellum, which contains more than half of the brain’s neurons and a significant source of input to language as well as motor cortical regions, provides a means by which residual cortical tissue can be stimulated in stroke participants without interference from the lesion itself. However, the effect of cerebellar tDCS combined with behavioral therapy remains incompletely understood. Further, little is known about how factors related to imaging and linguistic characteristics combine to induce treatment responsiveness. We will carry out resting state functional magnetic resonance imaging (rsfMRI), diffusion tensor imaging (DTI), high resolution structural imaging, and detailed linguistic testing before the start of treatment to determine whether these factors can predict response to cerebellar tDCS and/or SFA. This exploratory aim may identify stroke patients who are mostly likely to benefit from cerebellar tDCS and/or SFA. This result may have significant implications for designing a Phase III randomized controlled trial. We will look at the effect size estimates for the primary and secondary outcomes as well as the safety profile to inform the design of the phase III study. Trial results will be submitted to Clinicaltrials.gov no later than one year after the primary completion date. In addition, regardless of outcome, results will be disseminated in peer reviewed journals and contribute to the growing body of literature on the topic of tDCS in post-stroke aphasia rehabilitation.

Supporting information

S1 file. spirit checklist..

https://doi.org/10.1371/journal.pone.0298991.s001

S2 File. Protocol.

https://doi.org/10.1371/journal.pone.0298991.s002

S3 File. Consent form.

https://doi.org/10.1371/journal.pone.0298991.s003

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• 4. Raymer AM, Gonzalez-Rothi LJ, editors. The Oxford handbook of aphasia and language disorders. New York, NY: Oxford University Press; 2018.
• 49. Goodglass H, Kaplan E, Barresi B. BDAE-3: Boston Diagnostic Aphasia Examination–Third Edition. Philadelphia, PA: Lippincott Williams & Wilkins; 2001.

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Matcha Benefits: How This Superfood Can Transform Your Life

Posted by Ace Erediano on August 26, 2024

The benefits of matcha, a superfood, are not talked about enough. The versatile ingredient can be added to various foods and drinks to boost nutritional health—and it tastes great, too!

So, are you ready to discover all the matcha benefits? Let’s dive right in.

What is Matcha?

Matcha is a powdered green tea made from the leaves of the Camellia sinensis plant, more specifically, tencha leaves. 

These leaves are shaded for several weeks before harvesting to enhance their chlorophyll and amino acid content, particularly L-theanine. 

The process gives matcha its vibrant green color and unique flavor profile, which is slightly sweet, grassy, and mildly bitter. 

Unlike other types of green teas , matcha involves consuming the whole leaf in powdered form, providing a concentrated source of antioxidants and a unique range of vitamins and minerals, including: 

• Vitamins A, C, and E

Traditionally prepared by whisking with hot water to create a frothy, smooth tea, matcha is also versatile in culinary applications such as lattes, smoothies, desserts, and savory dishes.

The History of Matcha

Matcha has a profound history. The ingredient has led a fascinating journey over a millennium, originating in China and becoming an integral part of Japanese culture. 

Origins in China (7th-10th centuries)

The earliest roots of matcha can be traced back to the Tang Dynasty in China. During this period, tea leaves were steamed, dried, and formed into bricks to facilitate transportation and trade. 

To prepare the tea, pieces of these bricks were pulverized and mixed with hot water and salt, creating an early form of powdered tea.

Song Dynasty and the Rise of “Whisking Tea” (10th-13th centuries)

During the Song Dynasty, a new method of tea preparation emerged, known as “whisking tea.” This process involved grinding tea leaves into a fine powder and whisking them with hot water, creating a frothy beverage resembling modern-day matcha.

Introduction to Japan (12th century)

In 1191, a Japanese Buddhist monk named Eisai brought tea seeds from China to Japan, along with Zen Buddhist methods of preparing powdered green tea. Eisai planted these seeds on temple grounds in Kyoto, and they were considered to produce the highest-quality tea leaves in Japan.

Development of Tencha (shade-grown tea)

Soon after Eisai returned, Zen Buddhists in Japan developed a new method of cultivating green tea plants under shaded conditions called Tencha. This method maximizes all the matcha benefits.

Matcha and Zen Buddhism

Matcha became deeply intertwined with Zen Buddhism in Japan. Zen monks found that drinking matcha improved their meditation sessions, producing a state of calm alertness. Consuming matcha became a means of enlightenment and was incorporated into daily temple practices.

The Japanese Tea Ceremony (15th-16th centuries)

In the 1500s, a Zen student named Murata Juko formalized the tea ceremony ritual , later popularized by Zen Master Sen-no-Rikyu. The ceremony, known as “Chado” or “Sado,” incorporated four principles: 

• Harmony (wa)
• Respect (kei)
• Purity (sei)
• Tranquility (jaku)

Decline and Resurgence

During the Edo period (1603-1868), matcha’s popularity declined as commoners favored sencha, a more affordable green tea. Matcha became associated with the elite, primarily consumed by the aristocracy and samurai class.

In the late 20th century, matcha experienced a resurgence in popularity as matcha benefits gained global attention. Rich in antioxidants containing L-theanine, matcha is linked to various health benefits, including:

• Improved heart health
• Increased metabolism
• Reduced stress

Today, matcha has transcended its traditional roots and is enjoyed worldwide in various culinary applications, from traditional tea ceremonies to lattes, smoothies, and baked goods. Matcha’s unique taste, color, and health benefits have solidified its status as a beloved beverage and ingredient in modern cuisine.

How Matcha Is Different From Other Teas

Matcha is distinct from other teas in several ways.

Cultivation Method

Matcha tea plants are shade-grown for about 3-4 weeks before harvest. This shading process increases chlorophyll production, which gives matcha its green color and boosts its amino acid content, particularly L-theanine.

Unlike other teas, which steep leaves and discard them, matcha grinds the entire tea leaf into a fine powder. The process begins by removing the stems and veins and then stone-grinding the leaves into the characteristic matcha powder.

Preparation

Matcha is prepared by whisking the powder directly into hot water, typically using a bamboo whisk (chasen) in a special bowl (Dhawan). This preparation method is an integral part of Japanese tea ceremonies.

Our special edition matcha traveler gift box is ideal for anyone who can’t stay away from matcha, even when on the go! 

Consumption

When you drink matcha, you will consume the whole tea leaf (which is one of the main matcha benefits), not just an infusion. This results in a more concentrated intake of the nutrients and compounds found in the tea leaves.

Nutritional Profile

Due to its processing and unique consumption method, matcha has a higher concentration of certain compounds compared to other teas:

• L-theanine (responsible for the flavor and cognitive benefits)
• Catechins (a type of antioxidant)

Flavor Profile

Matcha has a distinct, rich, umami flavor with a slight bitterness. The taste difference between matcha and green tea is also noticeable, as the former has a more intense and complex flavor compared to the latter. 

Health Benefits of Matcha

Matcha benefits include improved mental clarity, a boost in metabolism, and a high concentration of antioxidants that support overall health. Let’s take a closer look at this superfood’s wide range of health benefits.

Concentration of Antioxidants

As mentioned, matcha is exceptionally high in catechins, particularly epigallocatechin gallate (EGCG). In fact, a study from the Pomeranian Medical University found that matcha contains up to 137 times more EGCG than other types of teas. These antioxidants offer several benefits, including:

• Antibacterial properties that could prevent tooth decay and bad breath.
• Protection of cells reduces the chances of chronic disease.
• Protection against UV radiation.
• Blood sugar regulation.

Additionally, catechins are beneficial for individuals with systolic blood pressure (the upper number) of 130 or higher, which is a risk factor for heart disease, heart attack, and stroke.

Boosts Metabolism

According to research from the University of Geneva , m atcha has thermogenic properties beyond its caffeine content. These properties can increase the body’s heat production from 8-10% to 35-43%, aiding in fat loss (if consumed as part of a healthy diet and exercise.)

The EGCG additionally promotes fat burn during exercise, allowing you to get more out of every workout.

Improves Brain Function

A study of the University of Tokyo has shown that matcha can improve cognitive functions, particularly in elderly individuals. A randomized, double-blind, placebo-controlled 12-week trial found significant cognitive enhancement in the Montreal Cognitive Assessment (MoCA) scores among elderly women who consumed matcha daily.

Matcha can potentially reduce the chances of contracting Alzheimer’s disease. The EGCG reduces the number of beta-amyloid plaques in the brain that are responsible for causing Alzheimer’s.

Reduce Risk of Heart Disease

Matcha’s antioxidants help reduce oxidative stress and inflammation, contributing to cardiovascular diseases. Many studies have shown this, including one by Virginia Polytechnic Institute and State University .  

By preventing the oxidation of LDL cholesterol, matcha helps keep arteries clear and reduces the risk of atherosclerosis.

Reduce the Risk of Some Cancers

A study from the University of Salford (UK) found that matcha green tea can help stop the growth of breast cancer stem cells. 

The researchers discovered that matcha affected the cancer cells’ energy production, slowing their main energy processes. This change made the cancer cells less active and less likely to grow.

Improves Digestion and Detoxing

Since matcha is made from ground leaves rather than steeping leaves in water, like other green teas, it contains higher amounts of fiber, catechins, and other nutrients. One study from Setsunan University demonstrated that participants who drank matcha tea for two weeks showed significant increases in beneficial gut bacteria. 

A Natural Stress Reliever

L-theanine promotes relaxation, reduces stress, and boosts alpha wave activity (located in the brain), which is associated with relaxed alertness. Research from the University of Shizuoka shows that matcha, due to its unique properties, has impressive stress-relieving effects. 

Matcha can reduce anxiety by activating dopamine D1 and serotonin 5-HT1A receptors in the brain. These receptors play essential roles in modulating anxious behaviors. 

Additionally, matcha reduces cortisol levels (the stress hormone)—no wonder the Japanese use it to stay calm during meditation.

The Best Ways to Enjoy Matcha Benefits

Incorporating matcha into your diet is an easy way to reap its numerous health benefits. 

Matcha Lattes

For those who prefer a creamier hot beverage, matcha lattes are an excellent choice. They combine the rich taste of matcha with the smoothness of milk.

Here’s a simple recipe for a delicious matcha latte:

• Scoop and sift 1-2 teaspoons of matcha powder into a cup or  matcha bowl .
• Add 2 ounces of hot water. Whisk your mixture until the matcha is fully dissolved and frothy.
• Heat and froth your choice of milk (dairy, almond, soy, or oat). We recommend using a milk f r other . Or, heat the milk on the stove and whisk it vigorously.
• Pour the steamed milk into your cup or matcha bowl and stir gently.
• Add sweetener to taste, such as honey, agave syrup, or vanilla extract.

Smoothies and Juices

Matcha is a versatile ingredient that’s the perfect addition to juices for a nutritional boost. 

Adding matcha to your morning smoothie is another excellent way to start the day with an energy lift. Here’s an easy-to-prepare matcha smoothie recipe:

• Ingredients:
• 1 teaspoon of matcha powder
• 1 cup of spinach
• 1 cup of almond milk
• A  handful of frozen berries
• Combine all of your matcha smoothie ingredients into a blender and blend until smooth.
• Pour the mixture into your favorite glass with ice and enjoy immediately. The matcha will provide a subtle green tea flavor while improving your smoothie’s nutritional profile.

Baking with Matcha

Add matcha benefits to your favorite baked goods like cakes, cookies, muffins, and bread.

Here’s a simple recipe for matcha cookies:

• 1 cup of flour
• 1/2 cup of sugar
• 1/2 cup of butter (softened)
• 1/2 teaspoon of baking powder
• In a small bowl, cream together your butter and sugar until it’s light and fluffy. 
• Add the egg and mix well. 
• Sift in the flour, matcha powder, and baking powder, and combine until a dough forms.
• Get your oven ready by preheating it to 350°F (175°C) 
• Roll your dough into small balls (or take 1 heaping tablespoon) and place them on a baking sheet. Flatten each ball slightly with a fork. 
• Bake for 10-12 minutes or until the edges are golden brown.
• Let your matcha cookies cool on a wire rack before enjoying them.

Matcha in Savory Dishes

Matcha is no alien to soups, salad dressings, and sauces. Here’s a recipe for a matcha-infused salad dressing:

• 2 tablespoons of olive oil
• 1 teaspoon of honey
• 1 tablespoon of lemon juice
• Top with a pinch of salt and pepper.
• In a bowl of your choice, whisk together the matcha powder and olive oil until well combined. Add the lemon juice, honey, salt, and pepper, and whisk until the dressing is smooth.
• Drizzle the matcha dressing over your favorite salad greens and toss to combine. This dressing pairs well with mixed greens, avocado, and roasted vegetables.

Matcha Ice Cream

For a refreshing dessert, try making matcha ice cream. This creamy treat is perfect for hot days and is a delightful way to incorporate matcha into your diet.

• 2 teaspoons of matcha powder
• 2 cups of heavy cream (or alternative)
• 1 cup of whole milk (or dairy-free alternative milk)
• 3/4 cup of granulated sugar
• 1 teaspoon of vanilla extract
• Whisk together the matcha powder and sugar in a bowl until well combined. Add the heavy cream, whole milk, and vanilla extract. Mix until the sugar is dissolved.
• Pour the matcha mixture into an ice cream maker. Churn your mixture according to the manufacturer’s instructions.
• Scrape your churned ice cream into a freezer-safe container. Freeze your matcha ice cream for at least two hours before serving.

You can also enjoy the matcha benefits with mochi (a popular Japanese dessert). 

Matcha Energy Balls

Matcha energy balls are an excellent option for a quick and healthy snack. These bite-sized treats are packed with energy-boosting ingredients and are perfect for on-the-go snacking. 

• One cup of old-fashioned rolled oats
• 1/2 cup of almond butter
• 1/4 cup of honey
• Handful of dark chocolate chips
• Combine the rolled oats, almond butter, honey, and matcha powder in a large bowl. Mix until all ingredients are well incorporated. Stir in the dark chocolate chips.
• Roll the matcha energy ball mixture into small round balls. 
• Line a baking sheet with your favorite brand of parchment paper. Place your matcha energy balls on top for baking.
• Refrigerate the matcha energy balls for at least 30 minutes to firm up before serving.

Matcha Oatmeal

Starting your day with matcha oatmeal is a wonderful way to boost your morning energy levels and enjoy the benefits of matcha.

Here’s how to make a delicious bowl of matcha oatmeal:

• 1 cup of rolled oats
• 2 cups of almond milk
• 1 tablespoon of honey
• Fresh fruit for topping
• Bring your almond milk to a simmer in a small saucepan (don’t boil). 
• Add in the rolled oats. Cook them over medium heat, stirring occasionally. Cook until the oats are tender and the mixture is creamy (about five minutes).
• Add in your matcha powder and honey until well combined.
• Pour the oatmeal into your favorite bowl and top with fresh fruit, such as berries, bananas, or kiwi.

Matcha Yogurt Parfait

A matcha yogurt parfait is a nutritious breakfast or snack option.

Here’s how to make one:

• 1 cup of Greek yogurt
• 1/2 cup of granola
• Handful of fresh fruit
• Combine Greek yogurt, matcha powder, and honey in a bowl. Mix until the matcha powder is fully incorporated and the yogurt is smooth.
• Layer the matcha yogurt with granola and fresh fruit in a glass jar.
• Enjoy immediately or refrigerate for later.

Matcha Chia Pudding

Matcha chia pudding is a healthy and easy-to-make breakfast or dessert. 

• 2 tablespoons of chia seeds
• 1 tablespoon of honey.
• Whisk the almond milk, matcha powder, and honey in a bowl until well combined. Add the chia seeds and stir well.
• Let the mixture sit for 10 minutes, then stir again to prevent clumping. Cover and refrigerate for at least four hours or overnight.
• Serve the chia pudding topped with fresh fruit or nuts.

Try These Recipes

Despite matcha’s versatility, the ingredient still holds firm to its roots and remains primarily associated with tea.

Authentic Matcha Tea

Assemble the components included in the Matcha Gift Set from Magic Hour to create a perfect cup of matcha. You will receive:

• Organic ceremonial matcha
• A bamboo scoop (Chashaku)
• A bamboo whisk
• A matcha bowl

A matcha lover’s paradise.

The quality of the matcha powder is paramount, and the set features matcha from Kagoshima, Japan. Celebrated for its purity and green hue, it promises a delightful taste and numerous matcha benefits.

Start the preparation by sifting 1-2 teaspoons of matcha powder into the matcha bowl. Sifting is crucial as it removes clumps, ensuring a smooth and frothy tea.

Next, heat water to about 175°F (80°C). It’s essential not to use boiling water as it can impart a bitter taste to the matcha. Pour approximately 2 ounces (60 ml) of this hot water into the bowl with the sifted matcha powder.

Use the bamboo whisk to whisk the matcha and water briskly in a zigzag motion (M or W shape) until the mixture becomes frothy. This usually takes about 20-30 seconds. 

The whisking process should create a smooth, frothy layer on top of the matcha, indicating that it is ready to be consumed. Sip the matcha directly from the bowl to fully experience the traditional tea ceremony.

Almond Matcha Tea

Use the Magic Hour set to prepare a perfect cup of Almond Matcha Green Tea . 

Begin by sifting 1-2 teaspoons of matcha powder into the bowl to remove clumps and ensure a smooth and frothy tea. 

Heat water to about 175°F (80°C) and pour approximately 2 ounces (60 ml) into the bowl. 

Using the bamboo whisk, briskly whisk the matcha and water in a zigzag motion until a frothy layer forms. Sip and enjoy the rich, nutty flavor directly from the bowl. 

This process enhances the matcha’s taste and brings a sense of tranquility to your tea-drinking experience.

Enjoy the Numerous Matcha Benefits Today

Matcha is a delicious beverage, possessing a powerhouse of health benefits.

Start experimenting with the matcha benefits by incorporating it into your daily diet in various forms, such as traditional tea, lattes, or even baked goods.

For an authentic matcha experience and high-quality products, visit Magic Hour and explore our exceptional range of tea offerings.

Begin your journey to a better, healthier lifestyle by embracing the nutritious benefits of matcha today!

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