To compare the physiological and psychological effects of psilocin taken orally by pill or sublingually by dissolving a tablet under the tongue to those of psilocybin taken by pill in healthy adults.

The primary goal of this study is to compare the physiological and psychological effects of psilocin taken orally by pill or sublingually dissolved under the tongue to those of psilocybin taken by pill. Twenty participants, ages 25 to 50, with one previous experience with psychedelics, and who meet all other inclusion and exclusion criteria at screening will be enrolled. After baseline assessments, participants will engage in preparatory visits with trained facilitators, followed by drug administration, supervised by the facilitators and a clinician who will conduct safety monitoring throughout. Participants will then complete assessment and integration sessions with the facilitators in order to help process the experience. The same preparation, procedures, integration, and supervision will be repeated up to three more times with each participant.

Inclusion Criteria:

• Age 25 to 50
• Comfortable speaking and writing in English
• Commit to attending all study visits and remote data collection tasks
• No planned surgeries during the study
• Had at least one prior experience with a psychedelic substance
• Generally mentally and physically healthy
• Agree to abstain from THC, CBD, or nicotine products during study

Exclusion Criteria:

• Participated in another clinical trial within 30 days of entry to this trial
• Regular use of medications that may have problematic interactions with psilocybin, including but not limited to dopamine agonists, MAO inhibitors, N-methyl-D-aspartate (NMDAR) antagonists, antipsychotics, and stimulants
• A health condition that makes study unsafe or unfeasible, determined by study physicians