Psilocybin has been studied for everything from depression and addiction to neuroplasticity and emotional wellbeing. Now researchers have added something unexpected to the list.
Seeing red. Blood boiling. Flying off the handle. You guessed it — aggression.
A new study published in Frontiers in Behavioral Neuroscience found that psilocybin significantly reduced aggressive behaviour in one of the most territorial fish species scientists study in the lab.
Of course, the research doesn’t mean magic mushrooms are about to become a treatment for angry fish. But it dělá offer a fascinating glimpse into how psychedelics influence social behaviour, conflict, and brain signalling across the animal kingdom.
More importantly, it gives researchers a new model for understanding how psilocybin affects behaviour beyond the human experience.
Why Scientists Turned to Fish
Psilocybin, the naturally occurring compound found in more than 200 species of mushrooms (primarily those belonging to the Psilocybe genus) is known to interact with serotonin receptors in mammals.
Through those receptors, it can influence mood, appetite, emotional processing, and behaviour. So far, its effects on animal social behaviour, however, have remained relatively unexplored.
That’s what led researchers in Canada to study the mangrove rivulus fish (Kryptolebias marmoratus), an unusual amphibious species known for being naturally aggressive.
Unlike many social animals, these fish rarely need much encouragement to start displaying territorial behaviour. For scientists, that makes them an ideal model. Their aggressive actions are easy to observe, and even subtle behavioural shifts can be measured with precision.
There’s another advantage too.
Mangrove rivulus fish are self-fertilising, producing genetically identical offspring. This allows researchers to rule out genetic variation as an explanation for behavioural differences. In other words, if the fish behave differently after receiving psilocybin, scientists can be more confident that the drug is responsible.
Co výzkumníci zjistili
The study was led by Dayna Forsyth, a research associate and former MSc student at Acadia University in Nova Scotia. The results were clear.
“We show that an acute, low dose of psilocybin significantly reduces activity and aggressive attack behavior during social interactions in adult mangrove rivulus fish, a species that is naturally highly aggressive,” said Forsyth.
To test the effects, researchers worked with three genetically distinct laboratory-bred fish lines.
One group received psilocybin exposure.
A second group served as stimulus fish for social interaction testing.
A third group was used to measure absorption and whole-body concentrations of psilocybin.
The experiment itself was relatively straightforward. Researchers first recorded each fish’s baseline behaviour by placing it in a tank alongside another fish. The pair could see and smell one another through a mesh barrier, but physical contact was prevented.
After observing interactions, the fish were separated.
Twenty-four hours later, the same fish were exposed to water containing dissolved psilocybin for twenty minutes before being returned to the testing tank with the same social partner.
Researchers then compared behaviour before and after treatment.
Less Fighting, Fewer Attack Behaviours
Following psilocybin exposure, the fish became noticeably calmer. Researchers observed lower overall activity levels and significantly fewer aggressive swimming bursts compared to untreated fish. These bursts are important because they represent a specific form of escalated aggression.
“Swimming bursts are high-energy attack behaviors that represent an escalation of aggression towards the stimulus fish without making physical contact,” explained senior author Dr Suzie Currie, a biologist at The University of British Columbia.
Not all aggressive behaviours disappeared. The fish continued to engage in lower-energy social displays, which are often used to assess rivals or communicate social information.
That distinction caught the researchers’ attention.
“Psilocybin’s calming effect appears to selectively reduce energetically costly, escalated behaviors while lower-energy social display behaviors remained largely unchanged,” said Forsyth.
“This suggests that this compound can selectively dampen escalated social conflict rather than shutting down behavior altogether.”
In other words, the fish weren’t sedated, they were still social. They simply became less likely to escalate interactions into costly confrontations.
A Rare Example of Anti-Aggressive Effects
According to the research team, this represents one of the first demonstrations of psilocybin producing a selective anti-aggressive effect in a vertebrate animal model. That’s notable because aggression is deeply tied to serotonin signalling, one of the primary systems influenced by psilocybin. Scientists have long suspected psychedelics may alter social behaviour in meaningful ways, but demonstrating those effects experimentally can be challenging.
The mangrove rivulus fish offered a unique opportunity to isolate and measure behavioural changes in a controlled environment. The findings suggest psilocybin may influence how animals balance social interaction against conflict, reducing the drive toward escalation while preserving normal behavioural communication.
That distinction could prove valuable for future research.
What Does This Mean for Humans?
The obvious question is whether calmer fish tell us anything useful about people.
The researchers urge caution because this was not a clinical trial. Obviously, fish are not humans, and results from animal studies cannot be directly translated into medical treatments.
Still, animal models play an important role in helping researchers understand underlying biological mechanisms. Many discoveries about the brain begin in species where variables can be tightly controlled before moving into human research.
The value of this study lies less in its immediate practical application and more in the questions it opens up.
If psilocybin selectively reduces escalated aggression in fish, what nervové dráhy are involved?
Which serotonin systems are responsible?
Why are some forms of social behaviour affected while others remain intact?
Those are questions that become far easier to investigate in controlled animal models than they do in human participants.
The Bigger Picture
As psychedelic science matures, researchers are increasingly interested in understanding not only how psilocybin affects mood, but how it influences broader patterns of behaviour.
Social interaction is a major part of that puzzle. Human conflict, addiction, depression, trauma and emotional regulation all involve social dimensions. Understanding how psilocybin changes the way organisms respond to stress, competition and social engagement could eventually deepen our understanding of its therapeutic potential.
This study also highlights something increasingly recognised throughout psychedelic research: psilocybin doesn’t simply suppress behaviour — it often appears to alter behavioural patterns in more nuanced ways.
Rather than switching systems off, it may help organisms respond differently. In this case, that meant fewer aggressive attacks without a loss of social interaction.
Co bude následovat?
The researchers acknowledge several limitations.
- The study only examined single-dose exposure and short-term effects.
- It didn’t explore repeated dosing, long-term behavioural changes or adaptation over time.
Future research will be needed to determine whether the reduction in aggression can be sustained and whether similar effects appear in other species.
For Currie, the most exciting questions are still ahead.
“Future studies can build on this work to explore how psilocybin alters neural signaling, which serotonin pathways are involved, and why some aspects of social behavior are affected while others are not,” she said.
“These are questions that are difficult or impossible to answer directly in humans.”
For now, one thing seems clear. Even in one of nature’s most aggressive little fish, psilocybin appears capable of turning down the temperature without shutting down the conversation.
It’s another intriguing piece of the puzzle as scientists continue exploring how this remarkable compound influences the brain, behaviour and social connection.
