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Why Are Placebos Used in Clinical Trials?
Shauni FitzgeraldMay 28, 2024 2:16:13 AM7 min read

Why Are Placebos Used in Trials?

In clinical trials, the quest for effective treatments meets the intricacies of scientific inquiry. At the core of these trials lies a seemingly paradoxical element: the placebo. 

What role does this inert substance play in rigorously evaluating new treatments? Why are placebos indispensable in shaping our understanding of treatment effectiveness? 

In this guide, we explore the significance of these inactive agents to discover how they contribute to scientific integrity and uncover their ethical implications in medical research. 

Table of Contents


What is Placebo in Clinical Trials?

A placebo in a clinical trial is an inactive substance, such as a sugar pill or saline solution, given to participants in a clinical trial. It looks like the actual treatment under study but lacks the active ingredients. 

The purpose of a placebo is to provide a comparison for evaluating the exact effects of the experimental treatment By giving some participants a placebo and others the active treatment, researchers can determine if the treatment’s effects are due to its active ingredients or simply the participants’ belief in the treatment, i.e., the placebo effect

Furthermore, placebos help ensure trial results are accurate and reliable, assisting researchers to determine the effectiveness of the treatment being tested.

Are Placebos Always Used in Trials?

The use of placebos in trials depends on several factors. They are typically utilized in double-blind, randomized controlled trials, where participants are randomly assigned to receive either the experimental treatment or placebo. 

This ensures unbiased results by preventing participants and researchers from knowing who gets the active treatment.

However, there are situations where placebos are not ideal. For example, in clinical trials, withholding treatment could pose ethical concerns or cause harm to participants. Indeed, in trials for life-threatening conditions, placebos are often replaced with standard treatments or active comparable treatments.

Additionally, placebos may not suit studies where the objective is to compare different dosages or formulations of a treatment, as participants receive varying levels of the active treatment. 

Further, they don’t suit trials whose conditions require established, effective treatments. In such cases, participants may be reluctant to participate if they know they will receive a placebo instead of a known effective treatment. This can lead to recruitment difficulties and ethical issues.

Benefits of Placebos in Trials:

Placebos are used in clinical trials to evaluate new treatments. We will highlight the three key benefits of placebos in clinical trials.

  • Reducing Bias in Clinical Outcomes

One of the main goals during clinical trials is to remove bias. This applies to both parties, i.e., researchers and participants. 

Experimenter bias often occurs when researchers consciously or subconsciously influence the outcome of an experiment. In such a case, placebos act as a baseline for researchers to distinguish between the treatments's actual and potentially biased effects. 

In addition, placebos reduce participant bias. They minimize a person's influence while taking the treatment. 

For example, a painkiller can be tested on participants using a true analgesic and a placebo. This way, researchers can easily distinguish how the placebo affects the psychological disposition of the participant, thus enhancing the objectivity of the study outcomes.

  • Assessing the Psychological Impact on Healing

Recent research provides evidence of the psychological effect placebos have on people. 

Neuroimaging shows that placebos can alter brain chemistry as they activate regions associated with pain receptors. These findings emphasize the relationship between the mind and the body in the healing process.

Understanding these mechanisms is significant in evaluating and testing new treatments. The effect on biological systems needs to be optimized for the treatment under study using appropriate dosage. 

By identifying the psychological pathways through which a placebo exerts its effects, researchers can design more effective, safe medications. 

Expectations and conditioning between patients and healthcare professionals are among the factors that contribute to the placebo response. 

In addition, the relationship between patients and healthcare providers or researchers can significantly improve patient outcomes. Positive or negative interactions between both parties also help analyze how well a treatment is going.

  • Enhancing Study Credibility and Ethical Standards

Placebo-controlled trials are the gold standard for clinical testing. They determine treatment efficiency, safety, recommended dosage, and mode of action. 

These trials help researchers identify confounding variables, so different variations are utilized to evaluate the treatment to avoid compromising patient or participant safety. 

According to ethical standards, participants cannot be deprived of effective, quality treatment solely for research reasons. Also, participants must be informed beforehand about placebo-controlled trials and the type of research being conducted. 

For example, placebo-controlled trials are justifiable when evaluating the superiority of a new treatment/method over existing ones. 

By incorporating placebo-controlled trials in research, scientists have numerous benefits for clinical outcomes, unbiased options, increased validity, reliability, and mechanism of action.

What Is a Placebo Group in Trials?

In trials, a placebo group consists of participants who receive an inert substance instead of the actual treatment. This group helps researchers distinguish between the effects of the treatment and the placebo effect. 

By comparing the outcomes between the two groups, researchers can determine the true efficacy of the tested treatment.

Criteria for Participant Selection

Participants in the placebo group are selected through randomization, which ensures fairness and reduces bias. Inclusion and exclusion criteria are established based on factors like age, medical history, and the condition being studied.

Random assignment to either the placebo or treatment group helps distribute potential confounding factors evenly. Blinding techniques may also be used to prevent bias. Before participation, individuals provide informed consent and acknowledge the possibility of receiving a placebo. 

Ethical considerations prioritize participant safety throughout the trial. This approach ensures fair and unbiased selection for the placebo group, enhancing the validity of the trial’s results.

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Methods of Maintaining Blindness in Trials

Several strategies are utilized to maintain the double-anonymized feature in trials. These are:

  1. Blinding procedures ensure treatments are indistinguishable.
  2. A double-dummy design assigns both active treatments and placebos.
  3. Blinding codes are known only to independent parties.
  4. Placebo run-in periods help identify placebo responders.
  5. Data monitoring committees oversee trial progress and blinding integrity.

These methods prevent researchers and participants from knowing who receives the placebo, reducing bias and ensuring reliable trial outcomes. 

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Analyzing Data from Placebo Groups

Analyzing data from placebo groups involves statistical methods to distinguish between the placebo effect and the treatment’s efficacy. Researchers compare outcomes between the placebo and treatment groups using t-tests or chi-square tests

These tests calculate the placebo response rate to quantify the placebo effect’s magnitude. 

Data analysis is done blindly to prevent bias. Statistical modeling techniques, such as regression, assess treatment-outcome relationships. Subgroup analysis explores factors influencing placebo responses. 

These methods ensure accurate interpretation of trial results and the identification of treatment effects.


Using placebos in trials is a cornerstone in pursuing reliable and ethical medical research. 

These inert substances provide a benchmark for evaluating treatment efficacy and uphold scientific integrity and ethical standards. Understanding the role of placebos is essential to comprehending the dynamics of trials in advancing healthcare innovation.

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Key Takeaways

  • Placebos are inert substances used in trials to compare the effects of experimental treatments with no active ingredients.
  • These substances help researchers evaluate treatment efficacy by distinguishing between their effects and the “placebo effect.”
  • Placebos are commonly used in double-blind, randomized controlled trials. Exceptions exist, especially in trials for life-threatening conditions.
  • Randomization and blinding are used to select participants for the placebo group and maintain trial integrity.

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Are Placebos Ethical in Trials?

Placebos do not affect the patient, so they should ideally not cause issues with the patient. However, the patient must be informed about the treatments they are taking. 

Even as we advance medical research, we remain alive to the ethical concerns revolving around the well-being of patients. This is vital because it lets us know whether the effect on the patient is entirely from the medicine or the “placebo effect.”

Are Placebos Used Today?

Yes, placebos are used widely in clinical trials. They act as a basic guideline for treatment testing on various patients.

In Which Group Is a Placebo Typically Used?

There are usually two groups: the experimental group and the control group. The control group enables comparisons. Some control groups are assigned a placebo treatment, while others are assigned the active treatment. Ultimately, an outcome is generated and compared among the different groups.


Shauni Fitzgerald

Shauni Fitzgerald, a seasoned Regulatory Affairs & Research Manager at Atlantia Clinical Trials, excels in clinical study design, regulatory submissions, and quality management. With a master's in Nutritional Sciences, she brings expertise and leadership to the field.