Publication bias in randomized trials of psilocybin for depression: a Robust Bayesian Meta-Analysis
Çağrı Özkurt
Study at a glance
AI-extracted from the abstract| Characteristics | Re-analysis of a living systematic review Randomized Open-label |
|---|---|
| Intervention | Psilocybin |
| Topics | Depression Psilocybin |
| Key findings | After accounting for publication bias, the effect of psilocybin on depression symptoms is about 41% smaller than originally reported, with a credible interval spanning zero. |
Abstract
A recent living systematic review in Nature Mental Health found psilocybin reduced depression symptoms across 12 randomized controlled trials, with pooled effect g = 0.90. The original analysis assessed publication bias using Egger’s test, non-significant — but this test has limited power with few studies and cannot produce a bias-corrected estimate. We re-analysed the same open dataset using Robust Bayesian Meta-Analysis (RoBMA), which simultaneously estimates evidence for a treatment effect, heterogeneity, and publication bias. We find moderate evidence for publication bias (Bayes Factor = 3.89). After accounting for selective reporting, the bias-corrected effect (g ≈ 0.53) is ~41% smaller than published, with a credible interval spanning to zero. This evidence dissipates when open-label studies are excluded, suggesting expectancy-driven artefacts rather than file-drawer suppression. These findings do not overturn the original conclusions but indicate greater uncertainty than the frequentist analysis implies.
Comparable studies
Other systematic reviews and meta-analyses on psilocybin for depression, most cited first.
| Study | Year | Design | Participants |
|---|---|---|---|
| Therapeutic effects of classic serotonergic psychedelics: A systematic review of modern‐era clinical studies Patients with cancer- or illness-related anxiety and depression, major depressive... | 2020 | Systematic review | n = 188 |
| The experimental effects of psilocybin on symptoms of anxiety and depression: A meta-analysis People with elevated symptoms of anxiety and depression | 2020 | Meta-analysis | n = 117 |
| Psychedelics in the treatment of unipolar mood disorders: a systematic review Patients with broadly defined unipolar mood disorders | 2016 | Systematic review | n = 423 |
| Psychedelic therapy for depressive symptoms: A systematic review and meta-analysis. Participants in studies of psychedelic therapy for depressive symptoms (Major... | 2023 | Systematic review with meta-analysis | n = 14 |
| Serotonergic hallucinogens in the treatment of anxiety and depression in patients suffering from a life-threatening disease: A systematic review. Patients with life-threatening diseases and symptoms of anxiety or depression | 2018 | Systematic review | n = 445 |