A systematic review answers a defined question by searching the literature in a planned, recorded way, choosing studies by stated rules and judging their quality. Unlike an ordinary review, it aims to be reproducible: another team following the same method should find the same studies.
In psychedelic research, systematic reviews often conclude that the evidence is thin. A 2026 review of psilocybin mushroom and truffle microdosing found 11 articles covering 3,262 adults and rated certainty as low (Page et al., 2026). A 2021 review of drug treatments for PTSD, with searches up to October 2019, found nine trials and none of psilocybin (Varker et al., 2021). A 2024 BMJ review rated all included psilocybin depression trials at moderate risk of bias (Metaxa and Clarke, 2024).
A review is a snapshot: it covers only studies published up to its search date. Its conclusions depend on the quality of the studies it finds, and a review that pools numbers is also a meta-analysis.
Sources
- Page et al., Frontiers in Psychiatry, 2026
- Varker et al., Journal of Psychoactive Drugs, 2021
- Metaxa and Clarke, BMJ, 2024
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