In brief
- A team coordinated from Toronto has published a review of microdosing in healthy adults in CNS Drugs: 24 studies and 3,681 participants.
- In placebo-controlled randomized trials, there was no significant reduction in anxiety, depression, or stress.
- Adverse-event analyses were small and found no clear differences; that does not establish the absence of rare or delayed harms.
For years, microdosing has been a staple of public conversation, driven by a specific promise: sub-perceptual doses, taken on a schedule, to improve mood, focus, or creativity. A team of researchers from Canada, the Netherlands, the UK, and the US has now gathered all available evidence. The conclusion, published August 13 in CNS Drugs, is sobering: when measured in a double-blind setting, the effect is not clearly distinguishable from a placebo.
What was reviewed
The work, coordinated by St. Michael’s Hospital and the University of Toronto alongside colleagues from Leiden, Imperial College, and the University of Alberta, registered its protocol on PROSPERO and searched Embase, MEDLINE, and PsycINFO through February 2026. Of the 24 studies that met the criteria, only six provided sufficient data to calculate combined effects: two randomized placebo-controlled trials with 117 participants, and three observational studies without a control group, totaling 1,013 participants. This distinction matters more than it seems. Observational data primarily captures the experience of those who already believe in what they are taking; randomized trials attempt to neutralize that very expectation.
The numbers
In the placebo-controlled trials, the reduction in depressive symptoms was small and not statistically significant (standardized mean difference of -0.19). Anxiety also failed to reach significance and varied widely between studies (-0.20, with 82% heterogeneity). Stress levels remained virtually unchanged (0.02). While observational studies did point to improvements in mood and personality traits, these were based on imprecise estimates that the authors consider potentially influenced by expectations or lifestyle changes. When all study designs were combined, a downward trend in depression and stress appeared, though anxiety results remained unclear. Two trials with 109 participants contributed adverse-event data. No clear differences were observed; this does not establish equivalence or exclude long-term risks.
What it implies
This meta-analysis does not claim that microdosing does nothing. The randomized evidence was inconclusive and did not show consistent benefits for the measured symptoms. Nonsignificance does not establish placebo equivalence or expectations as the sole explanation. These findings are not necessarily applicable to high-dose, supervised protocols, where the mechanism and risk profile differ, nor to compounds like ibogaine, which operates in a different category. Those wishing to compare this with real-world practice can consult our pillar on microdosing. What is clear is that larger, better-blinded trials are needed before treating microdosing as a validated clinical intervention. One of the authors declares a leadership position in a company within the sector, a common occurrence that should be kept in mind from both perspectives.
Source
- Meshkat, S., Leung, M., Meshkat, S. et al. Efficacy and safety of psychedelic microdosing on psychological outcomes in healthy adults: a systematic review and meta-analysis. CNS Drugs, August 13, 2026.
Educational content written from a harm reduction perspective and with respect for individual freedom. It is not a substitute for advice from a healthcare professional and is not intended to encourage or condemn any drug use.
