A single dose of psilocybin eased symptoms of depression within days, with benefits lasting for more than three months compared to placebo, our new study has found. The study, published in the journal JAMA Network Open, involved 35 people with recurring depression. We randomly assigned participants to either receive psilocybin or a placebo. The placebo (vitamin B3) mimicked some physical effects of the psychedelic, such as temporary skin flushing.