Classical psychedelic microdosing, mood, and cognitive function: An umbrella review with narrative synthesis
Yiğit Özaydın, Buket Canlan Özaydın
Journal of Psychopharmacology June 28, 2026 DOI: 10.1177/02698811261456196 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Umbrella review with narrative synthesis Placebo-controlled Preregistered Peer reviewed |
|---|---|
| Sample size | 1,614 |
| Population | Adults in studies of microdosing effects on mood or cognition |
| Interventions | LSD psilocybin |
| Dose | ≤20 μg LSD or ≤3 mg psilocybin per session |
| Topics | Psilocybin Microdosing |
| Keywords | Mood Cognition Expectancy theory Systematic review Narrative review Clinical psychology Neurocognitive Psychotherapist Tolerability |
| Key findings | The only significant pooled effect was a small decrease in cognitive control; mood benefits were not replicated under placebo-controlled conditions. |
Abstract
Background: Psychedelic microdosing—repeated sub-perceptual doses of lysergic acid diethylamide (LSD) or psilocybin—has attracted scientific interest as a potential mood and cognitive intervention. The evidence base remains methodologically heterogeneous and vulnerable to expectancy bias.
Methods: We conducted an umbrella review with narrative synthesis following Joanna Briggs Institute guidance and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 standards (International Prospective Register of Systematic Reviews [PROSPERO]: 2020 standards (PROSPERO: CRD420251077340). Six databases were searched through February 2026. Eligible studies were systematic reviews and/or meta-analyses examining microdosing effects (⩽20 μg LSD or ⩽3 mg psilocybin per session) on mood or cognitive outcomes in adults. Quality was appraised with A Measurement Tool to Assess Systematic Reviews-2; primary-study overlap was quantified via corrected covered area (CCA).
Results: Three meta-analyses met quantitative criteria, drawing on 14 studies (13 unique samples, N = 1614); three reviews contributed to narrative synthesis. Primary-study overlap was very high (CCA = 0.29). The sole significant pooled effect was a small decrease in cognitive control ( d = −0.34, 95% CI: −0.62 to −0.06); all other domains were non-significant. No eligible meta-analysis provided pooled mood-outcome effect sizes within the microdose threshold; narrative evidence indicates that self-reported mood benefits are largely attenuated under placebo-controlled conditions. Short-term tolerability was acceptable, though cardiovascular signals and long-term risks via 5-HT 2 B activation remain uncharacterized.
Conclusions: Current evidence does not support cognitive enhancement through microdosing; the only consistent controlled finding runs counter to popular claims: microdosing was associated with a small but reliable impairment of cognitive control. Observed mood benefits are not replicated under blinded conditions, consistent with expectancy-driven responding. Adequately powered, preregistered, expectancy-controlled trials are required before clinical recommendations can be made.