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Related Experiment Video

Updated: Jan 13, 2026

How to Study Placebo Responses in Motion Sickness with a Rotation Chair Paradigm in Healthy Participants

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Published on: December 14, 2014

The placebome.

Henry K Philofsky¹, Isaac Mukamal², Kathryn T Hall³

¹Department of Psychiatry, University of Rochester Medical Center, Strong Memorial Hospital, Rochester, NY, United States.

Handbook of Clinical Neurology

|October 29, 2025

Summary

This summary is machine-generated.

Genetic variations in the "placebome" may confound randomized clinical trial (RCT) results. Differential genetic effects between drug and placebo arms can mask true treatment efficacy.

Keywords:

Clinical research Drug development Genetics Genomics Placebo Placebo genetics

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Area of Science:

Pharmacogenetics
Clinical Trial Methodology
Genetics and Personalized Medicine

Background:

Randomized clinical trials (RCTs) use placebos to control for nonspecific factors influencing outcomes, collectively termed the "placebo response."
A core assumption in RCTs is the additive nature of placebo and drug responses, with drug efficacy calculated as the difference between them.
Genetic variation is known to influence placebo effects and disease natural history, key components of the placebo response.

Purpose of the Study:

To review evidence on how genetic variation within the "placebome" (mediators of placebo response) can impact RCT outcomes.
To explore the potential for gene-by-drug/placebo interactions to confound treatment effect estimations.
To highlight the implications of genetic influences on placebo response for clinical trial design and interpretation.

Main Methods:

Literature review of existing evidence on genetic influences on placebo response components.
Analysis of how genetic variation might differentially affect outcomes in drug versus placebo arms of RCTs.
Examination of the concept of the "placebome" and its role in mediating placebo effects.

Main Results:

Genetic variation can influence placebo effects and the natural history of disease, contributing to the overall placebo response.
Little is known about how genetic variation modulates the effects of drugs (e.g., naloxone) that can alter placebo effects.
Differential genetic influences between treatment arms could lead to gene-by-drug/placebo interactions, potentially masking true drug efficacy.

Conclusions:

Genetic variation in the placebome presents a potential source of confounding in RCTs.
Understanding these genetic influences is crucial for accurate interpretation of drug efficacy.
Future research should investigate gene-by-drug/placebo interactions to refine clinical trial methodologies.