A systematic review and meta-analysis assessed the risk of psychedelic-induced psychosis in people with schizophrenia. Among population studies, the incidence was 0.002%; in uncontrolled trials, 0.2%; and in randomized controlled trials, 0.6%. In uncontrolled trials that included individuals with schizophrenia, 3.8% developed long-lasting psychotic symptoms. Of those who experienced psychedelic-induced psychosis, 13.1% later developed schizophrenia. The evidence suggests schizophrenia might not be an absolute exclusion for clinical trials on psychedelics for treatment-resistant depression and negative symptoms, but low study quality and limited data warrant a conservative approach until more research is done.
A systematic review and meta-analysis of randomized controlled trials found that MDMA-assisted therapy (MDMA-AT) was associated with reductions in PTSD symptom severity and dissociative symptoms, and may improve functioning, compared with control conditions. No clear benefit was observed for depressive symptoms. The analysis included 8 trials with 298 participants for the primary outcome. However, the overall certainty of the evidence was very low due to high risk of bias in outcome measurement, deviations from intended interventions, small sample sizes, and lack of active controls in most studies. Larger, higher-quality trials with active controls and long-term follow-up are needed to determine efficacy.