Psilocybin slows reaction times and impairs executive function during the acute phase, with effects scaling by dose

Psilocybin slows human reaction times and can mildly impair executive functioning during the acute phase of use, with the size of the effect scaling with dose. A systematic review and multilevel meta-analysis pooled data from 13 empirical studies (42 cognitive measures). Across tasks targeting executive components such as attention, working memory, conflict monitoring, response inhibition, and cognitive flexibility, participants showed longer response times versus placebo. Working memory appeared slightly more resilient at lower doses, while basic attention showed delays even in lower dose ranges. Accuracy changes were smaller and not statistically significant. The timing of cognitive testing within the acute window did not change the overall finding, with delays present both during peak effects and in adjacent hours. The authors discuss possible mechanisms including slowed sensory-motor processing, altered baseline attention, and dual-task interference from the subjective psychedelic experience. They also note limitations such as bias and publication bias, and emphasize supervision in medical settings to avoid situations requiring rapid reactions while effects are active.