Psilocybin calms aggressive fish without shutting down social behavior
In a study with mangrove rivulus fish, a single low dose of psilocybin reduced aggressive attacks and overall activity during social encounters. The fish still engaged in normal social behavior, suggesting the compound may specifically dampen escalating aggression rather than broadly suppressing behavior. The team calls the result the first demonstration in a vertebrate model that psilocybin can selectively lower aggression.
Psilocybin occurs in over 200 mushroom species, largely within the genus Psilocybe. In mammals, it acts on serotonin receptors tied to mood, appetite, and aggression, yet its effects on animal social behavior remain poorly understood. Researchers in Canada therefore tested it on mangrove rivulus, an amphibious fish known for intense aggression.
These fish can self-fertilize, yielding genetically identical young, which helps reduce inherited variation in experiments. The team used three lab-bred genetic lines and separated fish with a mesh barrier, allowing visual and chemical cues but no physical contact. A low acute dose reduced attacks and activity during social encounters.
This result may interest neuroscientists studying serotonin, aggression, and social behavior, as well as clinicians examining psilocybin’s therapeutic potential. If the effect translates beyond fish, it could suggest ways to target escalating aggression without broadly dulling social engagement. However, because the evidence comes from a single vertebrate species and low-dose exposure, any implications for human treatment or public health remain speculative and would require extensive further research.