Is microdosing a placebo? A rapid review of low-dose LSD and psilocybin research.
Level 1 - systematic review of randomized trials
Rapid systematic review of 19 placebo-controlled trials using Cochrane risk-of-bias assessment
PubMed 38877715 · doi:10.1177/02698811241254831
What was done
A rapid review of PubMed was conducted to evaluate all studies investigating psychedelic microdosing (LSD and psilocybin) with controlled doses and a placebo comparator. Methodological quality and bias were assessed across 19 identified placebo-controlled studies using the Cochrane risk-of-bias tool for randomised trials.
What was found
The abstract reports no numerical values or pooled effect sizes. The reviewed literature indicated that microdosing with LSD and psilocybin produced changes compared to placebo in neurobiology, physiology, subjective experience, affect, and cognition. The authors identified eight key methodological arguments against the view that microdosing is predominantly a placebo, noting evidence of dose-dependency and small measured effects of expectancy.
Why it matters
This review qualifies recent claims that microdosing benefits are entirely driven by expectation, showing that the current evidence base is too preliminary and limited to rule out genuine pharmacological effects.
Limits
The abstract provides no quantitative meta-analysis. The underlying studies are limited by small sample sizes, a limited number of total trials and doses tested, potentially sub-therapeutic dosing, lack of clinical populations, and susceptibility to selection bias.
Cited by
- supports Clinical trial evidence to date shows underwhelming efficacy for psychedelic microdosing.