This meta-analysis (2020) reported favorably on four trials (n=117) that studied the effect of psilocybin-assisted therapy for anxiety and depression.

Abstract

“The current meta-analysis examined the effects of psilocybin in combination with behavioral interventions on anxiety and depression in samples with elevated symptoms. Across four studies (one uncontrolled; three randomized, placebo-controlled; N = 117), within-group pre-post and pre-follow-up effects on anxiety and depression were large (Hedges’ gs=1.16 to 1.47) and statistically significant. Across three placebo-controlled studies, pre-post placebo-controlled effects were also large (gs = 0.82 to 0.83) and statistically significant. No serious adverse events were reported. Limitations include the small number of studies and risk for bias within studies. Results tentatively support future research on psilocybin for the treatment of anxiety and depression.“

Authors: Simon B. Goldberg, Brian T. Pace, Christopher R. Nicholas, Charles L. Raison & Paul R. Hutsong

Notes

“The current meta-analysis evaluated effects of psilocybin coupled with supportive behavioral interventions on anxiety and depression. Although a small number of studies were included, available data were promising. Within-group effects at post-treatment and six-month follow-up showed large reductions in anxiety and depression symptoms with no evidence of publication bias.”

“Additional large-scale studies examining the effects of psilocybin on treatment-resistant depression may be warranted, as only one of the four studies focused on this population. It may be valuable to evaluate various behavioral interventions to support or extend benefits of psilocybin treatments.”

The study didn’t get financial support directly, but two authors are affiliated with Usona Institute.

The studies included in the meta-analysis were:

Summary

Psilocybin in combination with behavioral interventions produced large and statistically significant effects on anxiety and depression in samples with elevated symptoms. No serious adverse events were reported.

Introduction

Several new treatment approaches have been developed for anxiety and depressive disorders in the past century, but some patients remain symptomatic, do not comply with treatment, or experience adverse side effects.

Researchers have recently resumed investigating psychedelic compounds as a novel treatment approach, including psilocybin, a plant alkaloid and 5-HT2A receptor agonist. A meta-analysis of clinical trials testing psilocybin for anxiety and depression was conducted.

2.8. Summarymeasures

Cohen’s (1988) d was computed for psilocybin groups alone, and Becker’s (1988) was computed for studies with a control condition. A pre-to-follow-up effect size was also computed for studies with psilocybin and control conditions.

2.9. Synthesisofresults

When multiple measures of anxiety and/or depression were included, effects were aggregated within study using the MAd package in R. Random effects models were employed.

3.2. Studycharacteristics

All four trials used randomized, placebo-controlled, cross-over designs, and included behavioral interventions pre-intervention visits, support during the administration of psilocybin or placebo, and postintervention support.

Sample sizes were small (M = 29.25, SD = 19.14), and retention was high (94.00% at post-treatment and 79.50% at follow-up).

3.3. Riskofbiaswithinstudies

All studies had high risk for detection bias due to limited blinding of participants and personnel, and attrition bias was high in three of four studies.

3.6. Riskofbiasacrossstudies

The effect sizes observed for within-group pre-post and pre- to follow-up effects were not inflated by a large number of unpublished studies with null results.

Discussion

The current meta-analysis showed that psilocybin combined with supportive behavioral interventions can reduce anxiety and depression symptoms. However, the study quality was high and there was evidence of publication bias.

Psilocybin had similar effects to psychological interventions and cognitive behavioral therapy on anxiety and depression in three randomized, double-blind, placebo-controlled studies. However, the effects were not robust to publication bias, highlighting the need for further placebo-controlled studies.

The current meta-analysis has several limitations, including a small sample size, heterogeneity in effect sizes and design features, high risk of bias, and limited racial/ethnic diversity.

Declarationofcompetinginterest

Christopher R. Nicholas and Charles L. Raison have received salary offsets from Usona Institute, and have served as consultants for Alkermes and Shire.