Related Experiment Videos
Placebo interventions for all clinical conditions
1Nordic Cochrane Centre, Rigshospitalet, Department 7112, Blegdamsvej 9, Copenhagen Ø, Denmark, DK-2100.
The Cochrane Database of Systematic Reviews
|July 22, 2004
Summary
This meta-analysis found no significant evidence that placebo interventions generally improve patient outcomes. A potential small effect on continuous patient-reported outcomes, particularly pain, could not be definitively separated from bias.
Area of Science:
- Clinical Trials and Evidence-Based Medicine
- Psychology and Behavioral Medicine
Background:
- The perceived efficacy of placebo interventions in improving patient outcomes is widespread but lacks robust evidence from randomized trials comparing placebo to no treatment.
- This study addresses the gap in evidence regarding the actual effects of placebo interventions.
Purpose of the Study:
- To systematically assess the overall effect of placebo interventions across various health conditions.
- To differentiate between patient-reported and observer-reported outcomes in placebo trials.
Main Methods:
- Conducted a comprehensive literature search across multiple databases (CENTRAL, MEDLINE, EMBASE, Biological Abstracts, PsycLIT) and contacted experts.
- Included randomized placebo-controlled trials with a no-treatment control group for any health problem.
- Two independent reviewers assessed trial quality and extracted data, contacting authors for additional information.
Main Results:
- Analysis of 156 trials (46 conditions) revealed no statistically significant pooled effect for binary outcomes (RR 0.95).
- For continuous outcomes (118 trials), a small overall effect was found (SMD -0.24), primarily on patient-reported outcomes (SMD -0.30), especially for pain and phobia, but with a substantial risk of bias.
- No significant placebo effect was observed for conditions like nausea, smoking, depression, asthma, hypertension, insomnia, or anxiety when analyzed in trials with three or more studies.
Conclusions:
- Current evidence does not support clinically important general effects of placebo interventions.
- A potential small effect on continuous patient-reported outcomes, particularly pain, remains inconclusive due to the inability to distinguish it from bias.