Psilocybin, the psychedelic compound found in more than 200 species of mushrooms, can reduce aggressive behavior in mangrove rivulus fish, according to a study from Canadian researchers. In experiments, fish exposed to a low dose of dissolved psilocybin for 20 minutes moved less and displayed fewer high-energy swimming bursts that signal an attack was escalating toward contact.
Researchers chose the mangrove rivulus fish because it is naturally highly aggressive and can fertilize itself, producing genetically identical offspring. This allowed the team to work with distinct laboratory lines and more confidently link behavioral changes to psilocybin rather than inherited differences. After establishing baseline interactions, the scientists placed fish in psilocybin-laced water and then observed them with the same opponent fish 24 hours later.
The calming effect appeared selective: intense, energetically costly attack behaviors decreased, while lower-energy social displays, such as head-on communication, remained largely unchanged. The authors describe this as the first evidence that psilocybin can selectively reduce escalated aggression in a vertebrate model without shutting down social interaction. They suggest findings could inform future research into how psychedelic compounds influence behavior, though the work is limited to fish and further study is needed. This article relies on one source, and no conflicting findings are noted.