Researchers tested whether psilocybin (the active compound in magic mushrooms) could treat obsessive-compulsive disorder using genetically modified mice that exhibit excessive grooming similar to OCD in humans. A single dose of psilocybin or psychedelic mushroom extract significantly reduced the excessive grooming behavior and anxiety in these mice, with benefits lasting up to six weeks. These findings suggest psilocybin may be a promising new treatment for OCD in humans, offering longer-lasting effects from a single dose compared to current medications.