A single 25 mg dose of psilocybin, combined with psychotherapeutic support, produced rapid antidepressant effects in people with moderate to severe recurrent major depressive disorder. Depressive symptoms, measured by the Montgomery-Åsberg Depression Rating Scale, improved significantly more in the psilocybin group than in the placebo group by day 8, with benefits lasting through day 42 but not at one year. Self-reported depressive symptoms showed improvement as early as day 2 and persisted for over three months. The treatment was generally well tolerated, though two participants experienced persistent severe anxiety requiring medical attention. These findings suggest psilocybin may offer a rapid and relatively durable antidepressant effect.
A single dose of psilocybin (0.3 mg/kg) did not produce a statistically significant increase in synaptic density across all fifteen healthy participants. However, those who received psilocybin in a therapeutic-like room reported more intense mystical-type experiences, longer-lasting psychological benefits, and showed greater increases in synaptic density in the frontal cortex and hippocampus compared to those dosed inside an MRI scanner. The findings indicate that environmental context modulates psilocybin's neuroplastic effects, with implications for psychedelic-assisted therapies.