Psychedelic-assisted therapies (Psilocybin and MDMA) for treatment-resistant psychiatric disorders

Objective: To describe the pharmacological mechanisms, clinical efficacy, and safety of psilocybin- and MDMA-assisted therapies for depression and post-traumatic stress disorder (PTSD), while critically examining the methodological limitations of current evidence. Methods: This narrative, non-systematic literature review was conducted between September and November 2026. PubMed/MEDLINE was searched for publications from January 2016 to November 2026. Randomized clinical trials, systematic reviews, meta-analyses, and studies addressing mechanisms of action and safety were considered. Twelve references were selected and qualitatively synthesized. Results: Psilocybin demonstrated significant reductions in depressive symptoms, with a moderate pooled effect size (Hedges' g = 0.66). Evidence specifically concerning treatment-resistant depression remains limited. MDMA-assisted psychotherapy showed significant reductions in PTSD severity in two phase 3 trials, with favorable response and remission rates. Both interventions presented acceptable tolerability under controlled clinical conditions, although transient adverse effects were frequent. Serious adverse events were reported particularly among individuals with pre-existing neuropsychiatric conditions. Major limitations included difficulties with blinding, expectancy bias, uncertain long-term efficacy, and limited population diversity. Conclusion: Psychedelic-assisted therapies represent promising investigational approaches in psychiatry. However, methodological limitations and safety uncertainties warrant clinical caution and further rigorous research before broader therapeutic implementation.