Across 23 human studies, rates of psychedelic-associated hypomania or mania ranged from 5.8% in controlled psilocybin therapy trials to 30% in naturalistic studies involving people with bipolar disorder. Among 7,478 participants, the rate of later transition to bipolar disorder was 4%, with no evidence that psychedelics uniquely triggered bipolar illness compared with other factors. Most manic symptoms were short-lived and self-limiting, with the highest risks seen in people with bipolar I disorder, family history of bipolar disorder, polysubstance use, and unsupervised psychedelic use.