Psilocybin occasioned mystical-type experiences: immediate and persisting dose-related effects.
Level 2 - randomized trial
Double-blind, randomized crossover dose-effect trial
PubMed 21674151 · doi:10.1007/s00213-011-2358-5
What was done
Double-blind randomized crossover dose-effect study evaluating oral psilocybin at five dose levels (0, 5, 10, 20, and 30 mg/70 kg) under supportive conditions. Eighteen adults (17 hallucinogen-naive) completed five 8-hour sessions at 1-month intervals, randomized to receive active doses in ascending or descending sequence (nine participants each) with placebo scheduled quasi-randomly. Participants wore eyeshades and were instructed to focus inward. Subjective outcomes were assessed immediately post-session, at 1 month, and at 14 months follow-up, supplemented by community observer ratings.
What was found
At 20 and/or 30 mg/70 kg, psilocybin induced mystical-type experiences in 72% of participants and extreme anxiety or fear in 39%. Acute and persisting effects increased monotonically with dose, with significant effects detected even at 5 mg/70 kg. At 1 month after the two highest doses, volunteers attributed substantial personal and spiritual significance and sustained positive changes in attitudes, mood, and behavior to the experience, with greater positive effects seen in the ascending sequence. These ratings remained undiminished at 14 months and were corroborated by community observers.
Why it matters
This study established a dose-response gradient for psilocybin-occasioned mystical experiences and demonstrated that high doses can yield enduring positive behavioral and psychological changes lasting over a year.
Limits
The sample size was very small (n=18), restricting statistical precision and generalizability. The cohort consisted almost entirely of healthy, hallucinogen-naive individuals tested in a specialized, highly supportive environment. Additionally, high doses triggered extreme anxiety or fear in over a third of participants, underscoring substantial acute psychological risks.
Cited by
- supports Approximately 30% of research volunteers in controlled psilocybin sessions report experiencing significant fear or anxiety for some duration of the session.
- supports The probability of experiencing very difficult or challenging reactions to psilocybin increases significantly between doses of 20 mg and 30 mg per 70 kg body weight.