Low-dose psilocybin selectively reduces aggressive attacks in highly combative mangrove rivulus fish without disrupting normal social behavior

Low-dose psilocybin significantly reduced aggressive attacks and overall activity in highly combative mangrove rivulus fish, while leaving lower-energy social displays largely intact. Canadian researchers exposed adult fish to psilocybin for 20 minutes and compared their behavior during interactions with the same conspecific before and after treatment. The fish showed fewer high-energy swimming bursts, which signal escalation toward attack, but continued normal social assessment behaviors. The study suggests psilocybin may selectively dampen escalated social conflict rather than suppressing behavior broadly. Its implications remain limited: the experiment used fish, examined a single brief exposure, and did not test repeated dosing, lasting effects, adaptation, or aggression treatment in humans. Further work is needed to identify the neural and serotonin pathways involved.