Psilocybin

Safety and precautions

Cancer risk

A large observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods study found no associations between lifetime use of psychedelics and lifetime diagnosis of either any cancer or hematologic cancer specifically.¹Barnett BS, Ziegler K, Doblin R, Carlo AD. Is psychedelic use associated with cancer?: Interrogating a half-century-old claim using contemporary population-level data. Journal of Psychopharmacology. 2022 Oct;36(10):1118-1128. 

Side effects or adverse events

Supervised use of psilocybin has shown few serious adverse events.²Lewis BR, Garland EL et al. HOPE: a pilot study of psilocybin enhanced group psychotherapy in patients with cancer. Journal of Pain and Symptom Management. 2023 Sep;66(3):258-269; Grob CS, Danforth AL et al. Pilot study of psilocybin treatment for anxiety in patients with advanced-stage cancer. Archives of General Psychiatry. 2011 Jan;68(1):71-8. A study of effects from more than 1000 administrations in 30 studies found only nine serious adverse events and “no suicide attempts during the acute phase and 3 participants engaged in self-harm during the post-acute phase.”³Romeo B, Kervadec E et al. Safety and risk assessment of psychedelic psychotherapy: s meta-analysis and systematic review. Psychiatry Research. 2024 May;335:115880.

Side effects reported in studies include “an increased risk for elevated heart rate, systolic and diastolic blood pressure for all dose range categories, as well as an increased risk of nausea during the acute phase. Other common side effects included headaches, anxiety, and decreased concentration or appetite.”⁴Romeo B, Kervadec E et al. Safety and risk assessment of psychedelic psychotherapy: s meta-analysis and systematic review. Psychiatry Research. 2024 May;335:115880. 

Some studies not specific to cancer have found impaired memory, executive function, and/or attention after use of psilocybin.⁵Basedow LA, Majić T et al. Cognitive functioning associated with acute and subacute effects of classic psychedelics and MDMA—a systematic review and meta-analysis. Scientific Reports. 2024 Jun 26;14(1):14782; Gouzoulis-Mayfrank E, Schreckenberger M et al. Neurometabolic effects of psilocybin, 3,4-methylenedioxyethylamphetamine (MDE) and d-methamphetamine in healthy volunteers. A double-blind, placebo-controlled PET study with [18F]FDG. Neuropsychopharmacology. 1999 Jun;20(6):565-81.

Though rare and typically accidental, mushroom poisoning is also a risk, and may lead to minor gastrointestinal illness (such as gastroenteritis), redness, warmth, and burning pain (erythromelalgia), rhabdomyolysisbreakdown of muscle tissue that releases a damaging protein into the blood, intestinal thickening or scarring (fibrosis), heightened reflexes (hyperreflexia), liver failure, renal failure, convulsions, or slow or rapid heart rate (bradycardia or tachycardia).⁶Lowe H, Toyang N et al. The therapeutic potential of psilocybin. Molecules. 2021 May 15;26(10):2948. 

Psychological side effects are also possible. “In patients with mental or psychiatric disorders, suicidal ideation and auto-mutilation are possible risks of magic mushroom ingestion and, though rare, have been documented in the literature. Another risk is the possibility of exacerbating psychotic symptoms.”⁷Lowe H, Toyang N et al. The therapeutic potential of psilocybin. Molecules. 2021 May 15;26(10):2948.

Psilocybin use in the context of medical/psychiatric support and therapy is advised. Some people using psilocybin have very negative experiences, even becoming physically aggressive or violent or needing medical help.⁸Carbonaro TM, Bradstreet MP et al. Survey study of challenging experiences after ingesting psilocybin mushrooms: Acute and enduring positive and negative consequences. Journal of Psychopharmacology. 2016 Dec;30(12):1268-1278. One review concluded that adverse effects of medical psilocybin are manageable when administered according to risk management approaches, but it also has an abuse potential appropriate for scheduling under the US Controlled Substances Act.⁹Johnson MW, Griffiths RR, Hendricks PS, Henningfield JE. The abuse potential of medical psilocybin according to the 8 factors of the Controlled Substances Act. Neuropharmacology. 2018 Nov;142:143-166.

Do not use (contraindications)

“Having psychotic disorders such as schizophrenic tendencies is a contraindication for undergoing psychedelic-assisted psychotherapy, particularly psilocybin-assisted psychotherapy.”¹⁰Lowe H, Toyang N et al. The therapeutic potential of psilocybin. Molecules. 2021 May 15;26(10):2948.