In the first trial of its kind, psilocybin therapy significantly reduced depression and improved quality of life in people with bipolar II disorder (BD-II). After one 10 mg session, 29% of participants entered remission; a second 25 mg dose brought even greater improvements. No mania or psychosis was triggered, countering long-held fears about psilocybin in BD-II. Adverse effects like nausea and anxiety were mild and temporary.