Publication bias in randomized trials of psilocybin for depression: a Robust Bayesian Meta-Analysis
Çağrı Özkurt preprint
A re-analysis of 12 randomized controlled trials on psilocybin for depression found moderate evidence of publication bias, with a bias-corrected effect size about 41% smaller than originally reported. The original analysis reported a large effect (g = 0.90), but after accounting for selective reporting using Robust Bayesian Meta-Analysis, the effect dropped to about 0.53, with a credible interval that includes zero. This evidence of bias disappeared when open-label studies were excluded, suggesting expectancy-driven effects rather than suppressed negative results. The findings do not overturn the original conclusions but indicate greater uncertainty than previously thought.