The primary psychoactive constituent of more than 200 species of mushrooms, and one of the most extensively studied classic psychedelics in modern clinical research.
Psilocybin is a prodrug rapidly dephosphorylated to psilocin, which acts as a partial agonist at serotonin 5-HT2A receptors. Activation of cortical 5-HT2A receptors is associated with altered sensory processing, changes in self-referential thought, and reduced activity in the default mode network.
Psilocybin-containing mushrooms have a long history of ceremonial use in Mesoamerica. Western scientific interest began in the 1950s, paused during decades of prohibition, and resumed with a wave of controlled clinical trials beginning in the early 2000s.
Contemporary trials have examined psilocybin-assisted therapy for treatment-resistant depression, end-of-life anxiety, and substance use disorders. Results are promising but preliminary, with ongoing questions about durability, blinding, and generalizability.
Physiological toxicity is low, but psychological risk is real: acute anxiety, confusion, and destabilization can occur, particularly in unsupported settings or in people with personal or family histories of psychosis.
Educational reference only. Nothing here is medical advice or a recommendation to use any substance.
