🍄 Magic mushrooms could calm aggression without side effects

A compound that, at low doses, calms the most aggressive individuals without making them apathetic: that is what psilocybin, the active substance in "magic mushrooms", appears to do in a particularly belligerent fish.

Found in more than 200 fungal species, this molecule interacts with serotonin receptors in the brain and can influence mood and aggression in mammals. But its precise role in social behavior remained unclear. A recent study shows that low doses selectively reduce the exacerbated aggression of the mangrove rivulus fish, without suppressing social interactions. This action targets energy-consuming attacks, but spares display behaviors.


The mangrove rivulus fish is an ideal model due to its high natural aggression and ease of observation.

During the experiment, one fish was placed with another fish serving as a stimulus behind an opaque divider. After five minutes, the divider was removed to observe the interaction. Twenty-four hours later, the same fish was exposed to dissolved psilocybin for twenty minutes, then reintroduced with the same stimulus fish. Behavior was monitored again. This repeated measures design allowed the team to compare each fish's behavior before and after exposure, controlling for individual differences.

Fish that received psilocybin moved less and exhibited less "bursting" (high-energy swimming bursts), energy-consuming attack behaviors. Interestingly, frontal displays, a low-energy social assessment behavior, remained unchanged. As the researchers explain, swimming bursts represent an escalation of aggression without physical contact, while displays are more about communication. This selective attenuation of costly actions indicates that psilocybin targets specific neural pathways involved in conflict escalation, not general activity.

These results provide the first evidence that psilocybin can selectively reduce exacerbated aggression in a vertebrate.

The study only examined single low doses over short periods. Long-term effects, repeated exposure, or adaptation remain unknown. Future work will need to determine whether the aggression reduction persists and explore why some behaviors are affected and others are not.

Building on this research, scientists will be able to better understand how psilocybin modifies neuronal signaling and which serotonergic pathways are involved.