Systematic review · 2025
Review of side effects reported in 42 psilocybin trials involving 1,068 people
- Original title
- Adverse event reporting and management in psilocybin therapy clinical trials: A systematic review to guide clinical and research protocol development.
- Authors
- Bukovsky D, Amaev A, Song J, et al.
- Journal
- Progress in neuro-psychopharmacology & biological psychiatry, 2025
- Molecules
- Psilocybin
- Conditions
- Depression, Anxiety, Substance use disorder, Healthy volunteers, Other
- Participants
- 1068
- Evidence grade
- Moderate
- Source
- Read the original paper
The question
How often do side effects happen in clinical trials of psilocybin, what kinds occur, and how serious are they?
What they did
Researchers searched three research databases (MEDLINE, Embase and APA PsycInfo) from their start dates up to June 5, 2024. They included 42 clinical studies, with 1,068 participants in total, that reported on adverse events after psilocybin was given in a controlled setting. They summarized common and uncommon side effects, serious adverse events, reports of suicidal thinking, how side effects were measured, and which ones needed medical treatment.
What they found
Commonly reported side effects were headache, short-lived rises in blood pressure, and nausea, which usually went away on their own. Medical treatment was needed only rarely. Serious adverse events were reported in 2 of the 42 studies and occurred only in participants who already had a depressive disorder; these included suicidal behaviour and hospitalization. The authors concluded that psilocybin appears to have a favourable safety profile when given in controlled settings.
The fine print
All 42 included studies were rated as having a high risk of bias, mainly because participants and researchers could often tell who received psilocybin. Trials generally enrol screened, relatively healthy volunteers, so rates of harm may not reflect what happens outside research settings. Ways of recording side effects differed across studies, which makes counts hard to compare, and this summary is based on the abstract only.
What it means
In supervised trial settings, psilocybin’s reported side effects were mostly mild and short-lived, but serious events did occur in people with depression, which supports careful screening and monitoring.
Evidence grade: Moderate. A systematic review that pools 42 clinical studies, but it mixes trial types, does not combine results statistically, and the authors judged every included study to be at high risk of bias.
This summary is based on the study’s published abstract.