Post-acute psychological effects of classical serotonergic psychedelics: a systematic review and meta-analysis
Psychological Medicine – November 04, 2020
Source: OpenAlex
Summary
Psychedelics like psilocybin and ayahuasca, potent hallucinogens, demonstrate substantial mental health benefits. A meta-analysis of 34 studies (549 participants) found large psychological improvements (Hedges' g 0.84-1.08) versus placebo in randomized controlled trials. These effects, potentially linked to neurotransmitter receptor influence on behavior, spanned psychiatry and clinical psychology, with moderation for clinical samples. No post-acute adverse effect was observed, advancing interest in these chemical synthesis and alkaloids for Psychedelics and Drug Studies.
Abstract
Abstract Background Scientific interest in the therapeutic effects of classical psychedelics has increased in the past two decades. The psychological effects of these substances outside the period of acute intoxication have not been fully characterized. This study aimed to: (1) quantify the effects of psilocybin, ayahuasca, and lysergic acid diethylamide (LSD) on psychological outcomes in the post-acute period; (2) test moderators of these effects; and (3) evaluate adverse effects and risk of bias. Methods We conducted a systematic review and meta-analysis of experimental studies (single-group pre-post or randomized controlled trials) that involved administration of psilocybin, ayahuasca, or LSD to clinical or non-clinical samples and assessed psychological outcomes ⩾24 h post-administration. Effects were summarized by study design, timepoint, and outcome domain. Results A total of 34 studies (24 unique samples, n = 549, mean longest follow-up = 55.34 weeks) were included. Classical psychedelics showed significant within-group pre-post and between-group placebo-controlled effects on a range of outcomes including targeted symptoms within psychiatric samples, negative and positive affect-related measures, social outcomes, and existential/spiritual outcomes, with large between-group effect in these domains (Hedges' g s = 0.84 to 1.08). Moderator tests suggest some effects may be larger in clinical samples. Evidence of effects on big five personality traits and mindfulness was weak. There was no evidence of post-acute adverse effects. Conclusions High risk of bias in several domains, heterogeneity across studies, and indications of publication bias for some models highlight the need for careful, large-scale, placebo-controlled randomized trials.