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Related Experiment Video

Updated: May 31, 2026

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

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

Published on: December 14, 2014

Placebo effects and the common cold: a randomized controlled trial.

Bruce Barrett¹, Roger Brown, Dave Rakel

¹University of Wisconsin, Madison, Madison, Wisconsin, USA. bruce.barrett@fammed.wisc.edu

Annals of Family Medicine

|July 13, 2011

Summary

Belief in echinacea treatment, not the herb itself, may shorten common cold duration and severity. This suggests the power of the placebo effect in managing cold symptoms.

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Area of Science:

Pharmacology
Immunology
Clinical Trials

Background:

The common cold is a widespread illness with significant public health impact.
Treatment efficacy is often debated, with a notable interest in herbal remedies like echinacea.
The influence of patient expectations and treatment allocation methods on outcomes requires further investigation.

Purpose of the Study:

To investigate the impact of echinacea treatment allocation on common cold severity and duration.
To compare open-label echinacea, blinded echinacea, blinded placebo, and no-pill groups.
To explore the role of patient beliefs in treatment outcomes.

Main Methods:

A randomized controlled trial involving 719 participants with new-onset common cold.
Four parallel groups: no pills, blinded placebo, blinded echinacea, and open-label echinacea.
Primary outcomes: illness duration and global severity. Secondary outcomes: neutrophil and interleukin-8 levels.

Main Results:

No statistically significant differences in illness duration or severity were observed between the four groups.
A subgroup of participants who believed in echinacea experienced shorter and less severe illnesses when receiving pills, irrespective of echinacea content.
Biomarker analysis (neutrophil count, IL-8 levels) did not reveal significant group differences.

Conclusions:

Patient beliefs and expectations may play a substantial role in perceived treatment effectiveness for the common cold.
The findings highlight the potential significance of the placebo effect in managing cold symptoms.
Further research into the psychological aspects of treatment is warranted for optimizing medical decisions.