A systematic review of research on psychedelics for ADHD identified only six studies meeting inclusion criteria. One randomized controlled trial found no statistically important difference compared to placebo. Three cross-sectional studies reported positive effects of psychedelics, and one found statistically important improvement measured by the Child Bipolar Questionnaire. A case study showed improvement in depressive symptoms and functioning with ketamine. The evidence is insufficient to recommend psychedelics for ADHD, and it remains unknown whether patients whose depression responds to ketamine also have ADHD. No research examined how psychedelics affect patient subgroups with different causes of symptoms.
A systematic review and meta-analysis of studies from 1960 to 2024 found that the psychedelic agent DMT produced a large overall effect on reducing substance abuse (g = 0.94). Effects were larger for drug use (g = 1.35) than for alcohol use (g = 0.65). Studies that included psychotherapy showed significantly greater effects (g = 1.38) than those without (g = 0.60). However, the included studies had high risk of bias and high heterogeneity, so the findings should be considered preliminary rather than proof of established efficacy.