Psilocybin mushrooms (Psilocybe spp.) are being tested in a phase II, double-blind, placebo-controlled trial enrolling 40 adults with major depressive disorder, using 2 mg psilocybin once weekly for 4 weeks, followed by an open-label phase. The study tracks changes in depression scores at 4 and 8 weeks, plus safety, tolerability, and longer-term follow-up out to 2 years. This trial is designed to finally test whether popular psilocybin microdosing routines produce measurable antidepressant benefits beyond placebo.