Review of microdosing research finds no cognitive boost, and a small dip in cognitive control

The question

Does taking repeated very small doses of LSD or psilocybin - too small to cause a noticeable trip - improve mood or thinking skills in adults?

What they did

The authors carried out an ‘umbrella review’: a review of existing systematic reviews and meta-analyses, rather than of individual trials. They searched six databases up to February 2026 and included reviews that looked at doses of 20 micrograms of LSD or less, or 3 milligrams of psilocybin or less, per session, in adults. Three meta-analyses met the criteria for pooled numbers, drawing on 14 studies (13 unique samples, 1,614 people in total), and three further reviews were described in words. Review quality was appraised with a standard tool, and the degree of overlap between the underlying studies was measured.

What they found

Overlap between the primary studies included in the different reviews was very high (corrected covered area = 0.29), meaning the reviews largely covered the same trials. The only statistically significant pooled result was a small decrease in cognitive control - the mental skill of focusing and resisting distraction (d = -0.34, 95% confidence interval -0.62 to -0.06). All other domains showed no significant effect. No eligible meta-analysis reported pooled mood effects within the microdose range, and the narrative evidence suggested that self-reported mood benefits largely faded once studies used placebo controls. Short-term tolerability was described as acceptable, but effects on the heart and long-term risks from activation of the 5-HT2B receptor remain uncharacterized.

The fine print

This is a review of reviews, so it inherits the weaknesses of the original trials, many of which were small and methodologically varied. The very high overlap between reviews means the same handful of studies were counted repeatedly, so the evidence base is narrower than the number of reviews suggests. No pooled mood effect size was available within the microdose range, and long-term safety was not assessed. This summary is based on the abstract only.

What it means

At present, the controlled evidence does not support the popular claim that microdosing sharpens thinking; if anything, one measure of mental control was slightly worse, and reported mood benefits appear to shrink when people do not know whether they took a drug or a placebo.

Evidence grade: Moderate. An umbrella review pooling three meta-analyses of mostly small trials, with very high overlap between the underlying studies and no pooled mood results.

This summary is based on the study’s published abstract.