Magnitude of response in treatment and control groups within psychedelic trials for psychiatric disorders: A meta-analysis
European Psychiatry January 1, 2026 Shakila Meshkat, Qiaowei Lin, Rachel Sousa-Ho et al.
Control groups in psychedelic-assisted psychotherapy trials show substantial symptom improvement, likely due to non-specific factors such as expectancy and concurrent psychotherapy. A meta-analysis of 14 randomized controlled trials (643 participants) found that treatment groups had greater symptom reductions than control groups for depressive symptoms, PTSD symptoms, and anxiety symptoms. For PTSD, inactive placebo groups showed larger within-group improvements. The findings underscore the need for robust control conditions and careful interpretation of treatment effects in psychedelic research.