Direct Comparison of Altered States of Consciousness Induced by LSD and Psilocybin

Randomised, quadruple-blind, within-subject crossover in healthy volunteers (n=28) comparing single oral doses of LSD (0.1 mg, 0.2 mg), psilocybin (15 mg, 30 mg) and placebo with washout between sessions.

Aims are to directly compare subjective altered states and related brain measures (functional imaging) and to explore receptor-profile differences between LSD and psilocybin for basic neuroscience purposes.