A randomized, double-blind, placebo-controlled single-ascending-dose study to identify a non-hallucinogenic dose of psilocybin in healthy adults

This Phase I randomised, double-blind, placebo-controlled single-ascending-dose trial (n=56) in healthy adults tested low doses of psilocybin and found dose-related subjective effects and pupil dilation, but no serious side effects, hallucinations, or measurable cognitive decline. Subjective effects became distinguishable from placebo at 2.5 mg or below, suggesting low doses may separate psilocybin’s pharmacology from its hallucinogenic effects.