Summary: Psilocybin, the psychoactive compound found in many “magic mushrooms,” is well known for altering mood and perception in humans. Its effects on social behavior in animals are less explored. A new study used an unusual and highly aggressive vertebrate model, the mangrove rivulus fish, to investigate how low doses of psilocybin influence social interactions and aggression.
The researchers report that a single, low dose of psilocybin acted as a selective calming agent: it markedly reduced high-energy attack behaviors while leaving lower-energy social signals and basic communication intact. Treated fish were less active overall but remained engaged with conspecifics, indicating a reduction in escalation of conflict rather than a general suppression of social behavior.
Key Facts
- Model organism: The mangrove rivulus (Kryptolebias marmoratus) is self-fertilizing and produces genetically identical offspring. Using isogenic lines let researchers isolate the drug’s behavioral effects from genetic variation.
- Selective de-escalation: Psilocybin specifically reduced swimming bursts—high-energy attack maneuvers—while leaving low-energy social displays, such as head-on communication, largely unchanged.
- Calming rather than sedating: Dosed fish showed lower overall activity but continued to communicate with partners, suggesting psilocybin dampened aggressive escalation without erasing social interest.
- Vertebrate evidence: This is the first demonstration in a vertebrate model that psilocybin can reduce escalated aggression while preserving social assessment behaviors.
- Serotonin connection: Psilocybin binds to serotonin receptors, and because serotonin pathways are evolutionarily conserved across vertebrates, findings in rivulus fish may offer mechanistic insight relevant to other species, including humans.
Source: Frontiers
Over 200 mushroom species, mainly in the genus Psilocybe, contain psilocybin. In mammalian brains, psilocybin binds to serotonin receptors and can alter aggression, appetite, mood, and other behaviors. Yet how psilocybin affects social interactions across animals remains poorly described. The new study, published in Frontiers in Behavioral Neuroscience, examines whether low-dose psilocybin changes social behavior in the amphibious mangrove rivulus fish.
“An acute, low dose of psilocybin significantly reduced activity and aggressive attack behavior during social interactions in adult mangrove rivulus fish, a species that is naturally highly aggressive,” said Dayna Forsyth, the first author and a research associate and former MSc student at Acadia University in Nova Scotia.
“These findings provide the first evidence that psilocybin can selectively reduce escalated aggression in a vertebrate without suppressing social interaction,” said senior author Dr. Suzie Currie, a biologist at The University of British Columbia.
Calm waters
Mangrove rivulus are innately territorial and show clear, energetically distinct aggressive behaviors when paired with conspecifics. Their predictable behavioral repertoire and ability to produce genetically identical offspring make them an excellent model for isolating pharmacological effects from genetic differences.
The researchers used three genetically distinct laboratory-bred lines. One line supplied focal fish exposed to psilocybin, a second provided stimulus fish for social interactions, and a third line was used to measure whole-body psilocybin concentrations and absorption.
In the behavioral assay, a focal fish was first placed in a tank with a stimulus fish separated by a fiberglass mesh barrier and an opaque cover. The opaque cover allowed a five-minute acclimation while preventing interaction. After removal of the cover, researchers recorded baseline social behavior. The same focal fish was tested 24 hours later after a 20-minute exposure to psilocybin dissolved in the water, then reintroduced to the same stimulus fish for a second interaction session.
Magic mushroom, mellow fish
Behavioral scoring focused on activity (time spent moving) and measures of aggression, especially swimming bursts—rapid, high-energy maneuvers associated with attack escalation. Fish exposed to psilocybin spent less time moving and performed fewer swimming bursts than control fish, while lower-energy communicative displays remained largely unchanged.
“Swimming bursts are high-energy attack behaviors that represent an escalation of aggression toward the stimulus fish without physical contact,” Currie explained. “Other aggressive behaviors, like head-on displays, function more as communication and social assessment and require much less energy.”
Forsyth added, “Psilocybin’s effect appears to selectively reduce energetically costly escalations while preserving the fish’s ability to assess and communicate socially. That pattern suggests the drug dampens the drive to escalate conflict rather than simply sedating the animal.”
Diving deeper
Non-human models such as fish are valuable for preliminary drug screening because they offer experimental control and can reveal neural and behavioral mechanisms that are difficult to study directly in humans. Results like these can guide future therapeutic research by clarifying which aspects of social behavior are most sensitive to psilocybin.
The authors caution that this study examined single, short-term exposures in fish and did not test clinical treatments. Results cannot be directly extrapolated to humans. The study did not assess long-term effects, repeated dosing, or potential adaptation over time; follow-up experiments are needed to determine whether the observed reduction in aggression persists with repeated or prolonged exposure.
“Future work can build on these findings to map how psilocybin alters neural signaling, identify the specific serotonin pathways involved, and determine why escalated aggression is affected while other social behaviors remain intact,” Currie concluded. “These are questions that are difficult or impossible to answer directly in human subjects.”
Key Questions Answered:
A: The researchers emphasize the effect was selective. If the fish were simply sedated, all social behaviors would decline. Instead, treated fish continued to communicate but reduced attempts to attack, indicating a specific reduction in escalated aggression rather than general impairment.
A: Direct extrapolation from fish to humans is not possible. However, the conservation of serotonin receptors across vertebrates suggests the drug may target neural circuits that transform frustration into escalated aggression—an area of interest for future therapeutic research.
A: Using genetically identical rivulus reduces variability from individual personality or genetic differences, giving a clearer view of how a drug changes behavior.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- The journal paper was reviewed in full.
- Additional context was provided by staff editors.
About this aggression and psilocybin research news
Author: Deborah Pirchner
Source: Frontiers
Contact: Deborah Pirchner – Frontiers
Image: Image credit: Neuroscience News
Original Research: Open access. “The magic of mushrooms: Psilocybin influences behaviour in the mangrove rivulus fish, Kryptolebias marmoratus” by Dayna Forsyth, Nicoletta Faraone, Simon G. Lamarre, and Suzanne Currie. DOI: 10.3389/fnbeh.2026.1767175
Abstract
The magic of mushrooms: Psilocybin influences behaviour in the mangrove rivulus fish, Kryptolebias marmoratus
Non-human models, including fish, are increasingly important for studying how pharmacological agents such as hallucinogens influence behavior, physiology, and cellular processes. These models reveal underlying mechanisms and help evaluate toxicology, efficacy, and safety.
This study used isogenic lineages of the amphibious mangrove rivulus, an emerging model species known for high activity and socially dynamic interactions. Because this species often exhibits aggression toward conspecifics, it is well suited to probe behavioral effects of low doses of psilocybin.
Researchers socially stimulated fish using pairs of size-matched individuals from different isogenic lineages and compared baseline behavior to behavior after a waterborne dose of psilocybin. Treatment caused a significant decrease in activity and in the frequency of swimming bursts—an escalated aggressive behavior—toward conspecifics, with modest effects on other behaviors.
The results also revealed considerable variation in behavioral response among individuals, suggesting that psilocybin’s effects were largely independent of genotype. Overall, this study demonstrates that psilocybin reduces aggression and activity in an emerging fish model and contributes to evidence supporting its potential for therapeutic translation in future research.