Is psilocybin safe, and why do clinical trials screen people so carefully?

Psilocybin can cause panic, confusion, nausea, headache and temporary increases in blood pressure and heart rate. Serious or persistent psychiatric reactions are also a concern, particularly in vulnerable people. Depression trials commonly exclude participants with a personal or close family history of psychosis and other conditions that could increase risk. This means a reassuring result in a screened study cannot be generalized to everyone with bipolar disorder, psychosis risk, significant cardiovascular disease or complex medication use. Screening, trained support and follow-up are part of the intervention, not optional extras.[1][2]

Safety also involves what happens after the session. In Goodwin’s treatment-resistant depression trial, suicidal thoughts or behavior and self-injury occurred across dose groups. That does not establish that psilocybin caused every event, but it makes “risk-free” an inappropriate description and underlines the need for monitoring in an already vulnerable population. Microdosing is a separate exposure pattern: the Cavanna placebo-controlled study did not demonstrate reliable benefits in well-being, creativity or cognition, and its short duration cannot establish long-term safety. A smaller dose should not be treated as proof of either effectiveness or freedom from risk.[3][4]