Psilocybin — Classic psychedelic / serotonin 5-HT2A agonist

The key pharmacological insight is that psilocybin's effects require a "therapeutic container" — set (mindset), setting (environment), and psychological support. As a standalone pharmacology discussion, raw 5-HT2A agonism cannot explain outcomes; the phenomenological experience and therapist integration sessions are integral to efficacy. SSRIs (especially long-term) blunt psilocybin effects via 5-HT2A receptor downregulation — patients may need a 2-week SSRI taper for full effect.

Overview

This page is part of Hormonaly's evidence-graded compound library. All clinical claims are linked to peer-reviewed sources via our dual-layer citation verification pipeline.

Compound Class

Classic psychedelic / serotonin 5-HT2A agonist

Mechanism of Action

Full agonist at 5-HT2A serotonin receptors in prefrontal cortex; rapidly dephosphorylated to psilocin (active form). Produces neuroplasticity via BDNF/TrkB upregulation, default mode network (DMN) suppression, and increased global neural connectivity ("entropic brain" model). FDA Breakthrough Therapy for treatment-resistant depression (2018) and MDD (2019). Phase 2 data (COMPASS Pathways): 25mg psilocybin produced 29% remission rate vs 8% placebo at 3 weeks in TRD. Phase 3 ongoing. NOT FDA-approved.

Regulatory Status

Investigational — Phase 3 ongoing; Oregon and Colorado legalized for supervised use

Evidence Level

Moderate — Phase 2 RCTs; FDA Breakthrough designation; NOT yet Phase 3 complete