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Lessons learned from placebo groups in antidepressant trials.

Meike Shedden Mora¹, Yvonne Nestoriuc, Winfried Rief

¹Department of Clinical Psychology, Philipps University of Marburg, Marburg, Germany. m.shedden@staff.uni-marburg.de

Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences

|May 18, 2011

Summary

Investigator expectations significantly influence placebo and nocebo effects in antidepressant trials. Optimizing patient expectations is crucial for improving clinical trial design and outcomes.

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Area of Science:

Psychiatry
Clinical Psychology
Psychopharmacology

Background:

Placebo and nocebo phenomena are critical in antidepressant trials.
Methodological factors and participant/investigator expectations influence outcomes.

Purpose of the Study:

To review placebo and nocebo phenomena in antidepressant trials.
To analyze factors influencing placebo and nocebo responses.

Main Methods:

Meta-analysis of 96 randomized placebo-controlled antidepressant trials.
Moderator analyses examining publication year, rating type, and gender.

Main Results:

Large placebo responses observed, particularly in observer ratings, increasing with publication year.
Nocebo symptoms mirrored expected drug side effects, with gender differences noted.
Investigator expectations strongly influenced observer-rated placebo responses.

Conclusions:

Placebo and nocebo effects are significantly shaped by expectations.
Clinical trial designs should aim to optimize positive expectations and minimize negative ones.
Understanding these phenomena is key for accurate antidepressant efficacy assessment.