Psilocybin, a classic psychedelic, shows both short-term and long-term antidepressant effects for major depressive disorder and depression related to life-threatening diagnoses. A systematic review and meta-analysis of 10 clinical trials, including 524 adult patients, found a large effect size favoring psilocybin over control conditions. Therapeutic effects increase with higher doses. Adverse events are generally temporary and reversible, though serious events can occur. Psilocybin holds promise as a complementary or alternative therapy for depression.
A meta-analysis of 15 randomized controlled trials with 798 participants found that ketamine treatment for substance use disorder (SUD) significantly improved abstinence rates in the short term (less than one month), but not at one to six months. Dropout rates and adverse events did not differ significantly between ketamine and control groups, though the available evidence was too limited to establish safety conclusively. The authors conclude that current evidence suggests a short-term efficacy signal for ketamine in SUD, but remains insufficient to establish its efficacy and safety definitively.