Participants will complete two all-day study sessions, the first with placebo and the second with a moderately-high dose of psilocybin.

Preparation will include two days of screening and 8 hours of session preparation over at least 2 days, before the first all-day session. Follow-up will consist of an interview and MRI scan one day after each all-day session, a questionnaire follow-up 2 months after each all-day session, and a final follow-up 12-18 months after the second all-day session.