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Placebo Effect

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The “gold standard” for testing interventions in people is the “randomized, placebo-controlled” clinical trial, in which volunteers are randomly assigned to a test group receiving the experimental intervention or a control group receiving a placebo (an inactive substance that looks like the drug or treatment being tested). Comparing results from the two groups suggests whether changes in the test group result from the treatment or occur by chance.

The placebo effect is a beneficial health outcome resulting from a person’s anticipation that an intervention will help. How a health care provider interacts with a patient also may bring about a positive response that’s independent of any specific treatment.

Research supported by NCCIH has explored several aspects of the placebo effect. One study identified a genetic marker that may predict whether someone will respond to a placebo, another supported the idea that placebo responses may occur outside of conscious awareness, and a third suggested that placebos may be helpful even if patients know they’re receiving placebos.

For More Information

NCCIH Clearinghouse

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

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

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

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

Email: info@nccih.nih.gov (link sends email)

Know the Science

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

Explaining How Research Works (NIH)

Know the Science: 9 Questions To Help You Make Sense of Health Research

Understanding Clinical Studies (NIH)

PubMed®

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

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

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

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

Last Updated: January 2020