A single dose of psilocybin eased depression within days, but its edge over placebo faded within a year

Key Points:

• A randomized clinical trial in Sweden found that a single 25-mg dose of psilocybin produced rapid antidepressant effects in patients with moderate to severe recurrent major depressive disorder, with effects appearing by day 2 and lasting over three months on self-reports.
• The study involved 35 adults who received either psilocybin or an active placebo (niacin) alongside psychotherapeutic support, and depressive symptoms were assessed over a year using clinician-rated and self-report measures.
• Psilocybin showed a greater reduction in depressive symptoms compared to placebo by day 8, with remission rates at day 42 significantly higher in the psilocybin group (53% vs. 6%), though differences faded by one year.
• Psilocybin was generally well tolerated, with mostly temporary side effects, but two participants experienced severe anxiety requiring medical attention; blinding largely failed as most participants and clinicians correctly guessed treatment assignments.
• The study suggests psilocybin may offer rapid and relatively long-lasting antidepressant effects, but its small sample size, blinding issues, and recruitment methods limit conclusions about long-term benefits, warranting further research.