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.

Woman receiving an injection
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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.

2 Sources
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  1. Food and Drug Administration. Basics About Clinical Trials.

  2. American Cancer Society. Placebo Effect.

Additional Reading

By Adrienne Dellwo
Adrienne Dellwo is an experienced journalist who was diagnosed with fibromyalgia and has written extensively on the topic.