GLOSSARY · CHEMISTRY AND THE BODY

Psilocybin

A tryptamine made by certain mushrooms and named by Albert Hofmann’s team in 1958–59. The body converts it to psilocin, which acts on serotonin 5-HT2A receptors. In Canada it is a Schedule III controlled substance.

Full article: What is psilocybin, and how does it work? What the science shows and what it doesn’t

Psilocybin is the main psychoactive compound stored in Psilocybe and some other mushrooms. In March 1958, Hofmann and colleagues reported it from Psilocybe mexicana (Hofmann et al., 1958), and a 1959 paper described psilocybin and psilocin in crystalline form (Hofmann et al., 1959). Mushrooms build it from the amino acid tryptophan with four enzymes, PsiD, PsiK, PsiM and PsiH (Fricke et al., 2017).

In the body it is a prodrug: alkaline phosphatase removes its phosphate to make psilocin, the form that acts on 5-HT2A receptors (Dinis-Oliveira, 2017). Amounts in mushrooms vary widely; a 2026 study of 14 P. cubensis strains grown under the same conditions found total tryptamines varied more than 7.8-fold (Sharchaton et al., 2026).

Clinical trials use synthetic psilocybin, and results are mixed so far (Goodwin et al., 2022). Health Canada says there are no approved therapeutic products containing psilocybin in Canada or elsewhere (Health Canada), and it is listed in Schedule III of the Controlled Drugs and Substances Act (CDSA). This is not medical or legal advice.

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Last checked October 26, 2026.