Researchers tested psilocybin (the active compound in magic mushrooms) in mice bred to show obsessive-compulsive behaviors. A single dose of psilocybin reduced compulsive grooming for about a week, but giving it repeatedly over time did not help with anxiety, depression, or compulsive behaviors. The findings suggest psilocybin might work best as a one-time treatment rather than repeated doses, which has implications for how these drugs might be used in future psychiatric treatment.