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Negative Effects During Placebo Treatment: A Systematic Review and Meta-Analysis.
Tom Bschor1,2, Josephine Unger3, Lea Nagel1,4
1Department of Psychiatry and Psychotherapy, University Hospital, Technical University of Dresden, Dresden, Germany.
JAMA Psychiatry
|April 16, 2025
Summary
Negative effects of placebo treatment vary significantly across psychiatric diagnoses. Schizophrenia showed the highest dropout rates, while major depressive disorder had the lowest, indicating differential nocebo effects in clinical trials.
Area of Science:
- Psychiatry and Clinical Psychology
- Pharmacology and Therapeutics
Background:
- Placebo groups in clinical trials offer a unique transdiagnostic comparison point.
- Previous meta-analyses show placebo response varies across psychiatric diagnoses.
- Comprehensive transdiagnostic comparisons of placebo-associated negative effects (nocebo effects) are lacking.
Purpose of the Study:
- To compare premature study termination rates in placebo groups across nine major psychiatric disorders.
- To analyze total dropouts, dropouts due to adverse events, and dropouts due to lack of effect.
Main Methods:
- Systematic review of high-quality, recent placebo-controlled randomized clinical trials (RCTs) for nine psychiatric diagnoses.
- Selection of 10 RCTs per diagnosis, totaling 90 RCTs.
- Meta-analysis of pooled dropout rates (DRs) with 95% CIs, using random-effects models.
Main Results:
- Dropout rates differed significantly between diagnoses (Q=82.2, P<.001).
- Schizophrenia (DR=0.41) and mania had the highest total dropout rates and dropouts due to lack of effect.
- Major depressive disorder (MDD) and attention-deficit/hyperactivity disorder (ADHD) had the lowest dropout rates, with MDD showing the most favorable course under placebo.
Conclusions:
- Placebo treatment is associated with diagnosis-specific adverse effects, primarily lack of effect.
- Schizophrenia exhibits the least favorable course under placebo, whereas MDD demonstrates the most favorable.
- Findings highlight the importance of considering diagnostic variations in placebo response and nocebo effects.
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