Psilocybin: Compound Guide

Urgent first. If someone has eaten a mushroom and is confused, very agitated, vomiting repeatedly, has chest pain, a seizure or trouble breathing, call 911 or US Poison Help at 1-800-222-1222. See poisoning: what to do first. Do not try to treat it at home. If someone is in a mental health crisis, call or text 988 in the US.

This page is education only. It gives no amounts, no sourcing advice and no way to identify mushrooms. Evidence labels used below: approved medicine, promising but limited, mixed, insufficient evidence, evidence of harm.

What psilocybin is

Psilocybin is a compound found in certain mushrooms that grow on nearly every continent. NIDA describes it as part of the group of drugs called psychedelics. [1] It is a compound, not a mushroom: the fungi that contain it are covered on psilocybin mushrooms, and the sclerotia sometimes called truffles on psilocybin truffles. Psilocybin and psilocin, along with related compounds, typically occur in most species of the genus Psilocybe. [2] Strength varies from one mushroom to the next, so no single figure describes any species or product.

Psilocybin acts as a prodrug, meaning the body converts it into the active form, psilocin. [3] NIDA says psilocin activates serotonin receptors, mainly the 5-HT2A receptor, and researchers think this accounts for much of the experience. [1] Psilocin has its own page: psilocin. Where it fits among substances: classic psychedelics.

History

NIDA cites evidence that Indigenous people in Central America used psilocybin-containing mushrooms in healing and spiritual rituals as far back as 3000 B.C. [1] That is history of use, not proof that the mushrooms treat any condition.

What research shows

Clinical studies use a synthetic or standardized psilocybin product with trained staff and psychological support. That is not the same as mushrooms from other sources. See clinical formulations vs nonmedical products.

• Approved medicine: none found. NIDA says the FDA granted Breakthrough Therapy designation to two psilocybin formulations being studied for depression. [4] That designation speeds development; it is not approval. We did not read an FDA approval, and the FDA's own pages should be checked for the latest.
• Major depressive disorder: promising but limited. In a 2023 randomized trial at 11 US sites, 104 adults with major depression got one study dose of synthetic psilocybin or a niacin placebo, each with psychological support. Depression scores fell about 12 points more with psilocybin on a 60-point scale at day 43. There were no serious treatment-related adverse events, but overall and severe adverse events were more common with psilocybin. People with a history of psychosis or mania were excluded. [5]
• Compared with an antidepressant. A phase 2 trial of 59 patients compared psilocybin therapy with six weeks of escitalopram; its 6-month follow-up did not assess safety. [6]
• Anxiety and depression with life-threatening illness: promising but limited. A Cochrane review of six small trials found classic psychedelics may reduce anxiety and depression compared with active placebo, with low-certainty evidence. [7]
• Microdosing: insufficient evidence. NIDA says research has not established microdosing as safe or effective. [1] A self-blinded study of 191 people found both groups improved with no significant difference between them. [8] See what is microdosing.
• Why caution is needed. People often can tell whether they got the drug, so blinding can fail. A review argues effect sizes in psychedelic trials are likely overestimated because of unblinding and high expectations. [9] Details: how to read a psychedelic clinical trial.

For other conditions see psychedelics for major depressive disorder and alcohol use disorder research.

Risks and adverse effects

• Common effects in trials. A meta-analysis of six trials (528 participants) found headache, nausea, anxiety, dizziness and raised blood pressure were more common than with comparison treatments. [10]
• Serious events. A review of 214 studies of classic psychedelics found serious adverse events in no healthy participants and in about 4% of participants with preexisting neuropsychiatric disorders, including worsening depression, suicidal behavior and psychosis. [11]
• Outside clinical settings. NIDA says psilocybin typically raises blood pressure and heart rate, which may be dangerous for people with heart conditions, and that people may take risks such as dangerous driving. It also says poor mental health outcomes may be more likely outside clinical use. [1]
• Addiction. NIDA reports that research to date suggests psilocybin does not typically lead to addiction. [1]
• Pregnancy. NIDA says there is no data on psilocybin safety in pregnancy. [1]
• Medicines. Some researchers suspect psychedelics may interact with serotonin-raising medicines, though NIDA calls reported cases exceedingly rare. [4] We give no combining advice. Ask your prescriber and never change a medicine on your own. See serotonergic medicines.

Quality and labeling

In a Portland, Oregon study of eight mushroom gummies, labeling was overall inaccurate: one product labeled psilocybin-free tested positive for psilocybin, and seven of eight contained psilocin. [12] See unverified mushroom gummies.

Legal status

Not legal advice; laws change. In the United States, psilocybin is listed in Schedule I of 21 CFR 1308.11 (eCFR, read 2026-10-22). [13] Oregon's Health Authority describes a state program of licensed psilocybin service centers and licensed facilitators (read 2026-10-22). It is a state-regulated service framework, not general medical approval. [14] Other countries and states: not verified. See psychedelic legal status.