In this single-arm Phase 2 study, the researchers are assessing the feasibility of the group retreat format for clinicians and explores different 'doses' of preparation. A sequential dose-escalation design is used. The study will recruit healthcare clinicians (physicians, nurses, nurse practitioners, physician assistants) aged 25-70 years currently in clinical practice with moderate or greater symptoms of depression and loss of meaning during the past 5 years. Each participant will be in a group cohort of 8, and 3 cohorts will be tested at each dose level. The objectives are safety, feasibility, mechanism testing, and outcomes.

This is a single-arm study that examines the feasibility of the group retreat format for clinicians and explores different 'doses' of preparation.

Population: Healthcare clinicians (physicians, nurses, nurse practitioners, physician assistants) aged 25-70 years currently in clinical practice with moderate or greater symptoms of depression (PHQ-9 ≥10) and loss of meaning during the past 5 years.

Study Design: Phase 2, non-randomized, sequential cohort dose-escalation study examining the optimal number of preparation sessions for group retreat psilocybin therapy. Three cohorts will receive different "doses" of preparation: Cohort 1 receives 7 total preparation sessions (6 virtual + 1 in-person), Cohort 2 receives 4 total preparation sessions (3 virtual + 1 in-person), and Cohort 3 receives 2 total preparation sessions (1 virtual + 1 in-person). Each cohort includes 3 retreats with 8 participants per retreat.

Sample Size: 72 participants total (24 per cohort, distributed across 3 retreats of 8 participants each) Study Duration: 18-24 months from enrollment of first participant to completion of final data analysis. Individual participant involvement spans approximately 8-10 months including 6-month post-retreat follow-up.

Primary Objectives: (1) Safety: Assess incidence and severity of challenging experiences and adverse events across preparation dose levels using the Challenging Experience Questionnaire (CEQ), adverse event monitoring, and psychiatric symptom scales (PHQ-9, GAD-7, C-SSRS). (2) Feasibility: Determine completion rates for preparation sessions at each dose level.

Secondary Objectives: (1) Mechanism Testing: Examine relationship between preparation dose, group cohesion, and challenging experiences. (2) Clinical Outcomes: Explore effects on depression and burnout for future power calculations. (3) Participant Preference: Assess participant-reported optimal preparation length.

Summary: Psilocybin therapy has demonstrated promising efficacy for symptoms of depression related to frontline work during the COVID pandemic for clinicians. The group retreat format offers potential advantages over individual treatment, including enhanced accessibility, reduced cost per participant, and potential therapeutic benefits from group cohesion and shared experience. However, a critical unanswered question concerns the optimal number of preparation sessions. A sequential dose-finding design is appropriate because: (1) the dose-response curve for preparation sessions in group format is unknown; (2) attrition/completion rate is a critical feasibility outcome, particularly for time-constrained healthcare clinicians; (3) the design allows protocol refinement between cohorts based on emerging data; (4) this approach is more scientifically honest about genuine uncertainty regarding optimal preparation dose than premature randomization; and (5) it seeks to establish a minimum effective dose of preparation for practical feasibility and future scalability.

Inclusion Criteria:

1. Healthcare clinicians (physicians, nurses, nurse practitioners, physician assistants) currently in clinical practice
2. Age 25-70 years
3. Loss of meaning single question "I used to find deep meaning in my work as a healthcare clinician, but during the past 5 years that sense of meaning has faded".
4. PHQ-9 score ≥10 (moderate symptoms of depression)
5. Ability to commit to all preparation sessions and retreat attendance
6. English fluency sufficient for group participation
7. Screening laboratory tests within acceptable limits, including liver function tests
8. Negative urine drug screen for non-prescribed psychoactive medications.
9. ECG with QTc <450 ms
10. Willing to taper and discontinue any supplements with serotonin-like properties, including but not limited to 5-HTP, St. John's Wort, and 'brain food' supplements.
11. For participants of childbearing potential, agree to use to use highly effective contraception. Highly effective contraceptive methods are defined as those that, alone or in combination, result in a low failure rate (less than 1 percent per year), including but not limited to implants, IUDs, contraceptive injections, or contraceptive pills.

Exclusion Criteria:

1. Personal or first-degree family history of psychotic disorder or bipolar I disorder
2. Personal major depressive episode prior to entering healthcare as a professional
3. Active suicidal ideation with intent or plan
4. Unstable medical conditions
5. Pregnancy or breastfeeding
6. Hypertension with BP systolic >150 or diastolic > 90