A systematic review of psilocybin-assisted therapy for substance use disorders identified four clinical trials (six articles) involving 151 patients, with doses from 6 to 40 mg. Three studies focused on alcohol use disorder and one on tobacco use disorder. In a pilot study (n=10), heavy drinking days decreased significantly. In another single-arm study (n=31), 32% achieved complete alcohol abstinence over an average of 6 years. A double-blind, placebo-controlled RCT (n=95) found significantly fewer heavy drinking days with psilocybin versus placebo. In a pilot study (n=15), smoking abstinence at 26 weeks was 80% and at 52 weeks 67%. All trials indicated beneficial effects, but larger RCTs are needed.
A systematic review of clinical trials found limited evidence that psychoactive tryptamines other than psilocybin and ibogaine are effective for treating substance use disorders. Four trials involving 176 patients with alcohol use disorder tested dipropyltryptamine and diethyltryptamine. Abstinence rates ranged from 10% to 38% at 26 weeks of follow-up, and severity of alcohol use did not differ between the tryptamine and control groups. Adverse effects were poorly reported. The review concludes that studies are scarce and show limited evidence for effectiveness in treating addictive disorders.