The investigators will compare the acute effects of LSD, psilocybin and placebo.
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.
Oral LSD 0.1 mg single-dose; crossover within-subjects
Oral LSD 0.2 mg single-dose; crossover within-subjects
Oral psilocybin 15 mg single-dose; crossover within-subjects
Oral psilocybin 30 mg single-dose; crossover within-subjects
Oral placebo single-dose; crossover within-subjects