Classical psychedelic microdosing, mood, and cognitive function: An umbrella review with narrative synthesis.

Area of Science:

• Neuroscience
• Psychopharmacology
• Evidence Synthesis

Background:

• Psychedelic microdosing, using sub-perceptual doses of LSD or psilocybin, is explored for mood and cognitive enhancement.
• Existing research is inconsistent and susceptible to placebo effects.

Purpose of the Study:

• To synthesize current evidence on the effects of psychedelic microdosing on mood and cognition.
• To evaluate the methodological quality and findings of systematic reviews and meta-analyses.

Main Methods:

• An umbrella review with narrative synthesis was conducted, adhering to PRISMA 2020 standards.
• Six databases were searched, including systematic reviews and meta-analyses of microdosing effects (LSD ≤20 μg, psilocybin ≤3 mg) on adult mood and cognition.
• Study quality was assessed using A Measurement Tool to Assess Systematic Reviews-2; primary study overlap was quantified.

Main Results:

• Three meta-analyses (14 studies, N=1614) and three narrative reviews were included.
• High primary study overlap (CCA=0.29) was observed.
• A significant small decrease in cognitive control (d=-0.34) was the only consistent finding; mood benefits were not supported under placebo-controlled conditions.
• Short-term tolerability was acceptable, but cardiovascular risks and long-term effects remain unknown.

Conclusions:

• Current evidence does not support cognitive enhancement from microdosing.
• Microdosing is associated with a reliable impairment in cognitive control, contrary to popular claims.
• Observed mood benefits are likely expectancy-driven, requiring further rigorous, controlled trials for clinical recommendations.