Efficacy and Safety of Psychedelics in Mental Disorder Cases: An Umbrella Review of Meta-Analyses of Randomized Controlled Trials

Abstract

Background: Psychedelic-assisted therapy is gaining renewed attention as a potential treatment for various mental disorders. Despite increasing numbers of randomized controlled trials (RCTs) and meta-analyses, a comprehensive synthesis of the evidence across different substances and indications is lacking. This umbrella review aims to evaluate the effectiveness and safety of psychedelic-assisted therapy—primarily psilocybin, MDMA, and LSD—across major psychiatric disorders, including depression, post-traumatic stress disorder (PTSD), and substance use disorders. Methods: We systematically identified and synthesized data from 23 meta-analyses encompassing over 100 primary studies. Outcomes were standardized and re-expressed as Hedges’ g to enable cross-study comparisons. Study quality was assessed using AMSTAR2, and certainty of evidence was evaluated via the GRADE framework. Results: The number of identified meta-analyses differed markedly depending on the substance and clinical indication: psilocybin for depression (n = 9) and MDMA for PTSD (n = 10) had the strongest evidence base, while fewer meta-analyses were available for LSD in alcohol use disorder (n = 2) and depression (n = 2), ayahuasca in depression (n = 2), and MDMA in autism spectrum disorder (n = 2). Psilocybin demonstrated large effect sizes in major depression (Hedges’ g ≈ 1.05), with some evidence of sustained benefits up to six months. MDMA showed very large effects in reducing PTSD symptoms (Hedges’ g ≈ 1.24), often after 2–3 sessions. LSD yielded short-term benefits for alcohol use disorder (OR ≈ 2.0), though effects declined over time. Across studies, adverse events were generally mild and transient, with no consistent signal for serious harm. Considerable methodological variability was observed, including small and sometimes overlapping samples, heterogeneity, risk of bias, and limited long-term data. These constraints should be taken into account when interpreting the overall findings. Conclusions: Current evidence supports the short-term efficacy and safety of psychedelic-assisted therapy for selected psychiatric disorders, particularly depression and PTSD. However, the low methodological quality of studies and most meta-analyses, as well gaps in long-term safety data highlight the need for high-quality studies.