Summary:
A coordinated multi-laboratory investigation published in Nature Neuroscience challenges widespread assumptions regarding the enduring behavioral benefits of psychedelic compounds in animal models. Neuroscientists across five independent laboratories at UC Berkeley, UCSF, and Stanford University conducted parallel, harmonized tests on mice to establish which behavioral effects of psilocybin are genuinely reproducible.
While acute effects, such as head-twitch responses, brief increases in avoidance behavior, and reduced fear expression, proved robust immediately following injection, pooled data showed zero replicable reductions in anxiety- or depression-like behaviors, social learning enhancements, or fear extinction 24 hours post-dose. The findings underscore the urgency of large-scale replication to combat publication bias in psychedelic research.
Key Facts:
- No Persistent Antidepressant or Anxiolytic Shifts: Pooled analysis across five laboratories revealed no statistically reproducible reductions in anxiety- or depression-like behaviors, nor alterations in social interaction or fear conditioning in mice 24 hours after a single dose of psilocybin.
- Robust Acute Signatures: Immediate physiological and behavioral markers, including the head-twitch response (HTR), transient anxiety-like avoidance behavior at 10 minutes post-dose, and acute fear suppression, were consistently replicated across all test sites.
- Failure to Reopen Social Reward Windows: The consortium found no empirical evidence supporting previous claims that psilocybin reopens critical developmental periods for social reward learning in adult rodents.
Source: UC Berkeley / Nature Neuroscience
Psychedelic medicine has captured intense public and scientific attention over the past decade. Early-phase human clinical trials suggest that psilocybin, the psychoactive alkaloid found in magic mushrooms, can produce rapid, long-lasting relief from major depressive disorder, treatment-resistant depression, and post-traumatic stress disorder (PTSD). However, animal trials attempting to model these therapeutic breakthroughs have frequently generated conflicting or irreproducible findings.
Because identifying the underlying neurobiological mechanisms of psychedelics is exceedingly difficult in humans, neuroscientists rely on rodent assays to track synaptic plasticity, dendritic spine turnover, and circuit remodeling. Yet, if animal behavioral models do not reliably mirror persistent therapeutic outcomes, the foundational assumptions guiding drug development become compromised.
To establish an objective, reproducible baseline, a consortium of neuroscientists across five laboratories at three Bay Area institutions, the University of California, Berkeley, the University of California, San Francisco (UCSF), and Stanford University, executed identical, parallel experimental protocols in mice. The goal was straightforward: determine which behavioral phenotypes attributed to psilocybin survive rigorous cross-laboratory replication.
Publishing in the November 2, 2026 issue of Nature Neuroscience, the consortium reported that a single dose of psilocybin failed to generate measurable, lasting behavioral improvements 24 hours after administration.
The Multi-Lab Parallel Design
Conceived by Stanford neuroscientist Robert Malenka, MD, PhD, the initiative brought together primary investigators from diverse specializations: Stephan Lammel, PhD, and Andrea Gomez, PhD (UC Berkeley); Vikaas Sohal, MD, PhD, and Mazen Kheirbek, PhD (UCSF); and Boris Heifets, MD, PhD (Stanford). Supported by an anonymous donor, the four-year effort spent an entire year securing federal regulatory approvals before commencing synchronized experiments in 2022.
Each laboratory acquired identical mouse strains, standardized dosing protocols (2 milligrams per kilogram of body weight), and executed identical behavioral testing batteries evaluating locomotion, open-field avoidance, social preference, fear learning, and stress-coping behaviors.
The pooled findings revealed a striking divergence between immediate drug effects and next-day behavioral states:
- Universal Acute Phenomena: Across all five laboratories, psilocybin reliably induced the classic 5-HT2A-receptor-mediated head-twitch response (HTR), a transient spike in avoidance behavior ten minutes post-injection, and immediate suppression of learned fear.
- Absence of 24-Hour Persistence: When tested 24 hours later, after the drug had been fully cleared from circulation, mice displayed no persistent reductions in anxiety-like behavior, no improvements in immobility metrics on classic antidepressant screens, no alterations in social preference, and no difference in fear retention.
- No Critical Period Reopening: The consortium specifically re-tested earlier published findings claiming psilocybin reopens a juvenile “critical period” for social reward conditioning in adult mice, finding no reproducible evidence for this effect.
“One of our main findings is that, at least with our experiments and doses used, the persistent effects of psilocybin across these behaviors was modest, if anything,” said Odilia Lu, a doctoral student at UC Berkeley and co-first author of the paper. “This really highlights the importance of multi-lab collaborations, such as this one, to better estimate a true underlying effect size accurately and reduce the risk of publication bias—that is, that positive results from single experiments, often with small sample sizes, are biasing the literature.”
Dissecting Lab-to-Lab Discrepancies and Rodent Assays
Although the five laboratories adhered to identical written methodologies, individual lab results still varied in statistical significance when evaluated in isolation. For instance, when evaluating classic behavioral despair assays (such as the forced swim test), two of the five laboratories observed statistically significant improvements, while three observed none.
Had those two laboratories operated alone, they would have likely published positive findings, inadvertently fueling positive publication bias while negative data remained tucked away in file drawers.
Furthermore, the researchers emphasize that rodent despair models possess significant clinical limitations. A mouse ceasing to swim in a water cylinder cannot adequately capture the multifaceted psychological dimensions of human clinical depression, existential distress, or subjective insights achieved during guided psychedelic sessions.
“I don’t necessarily think we need to move away from focusing on depression, because it seems like psilocybin is most promising for the treatment of the disorder,” Lu noted. “A lot of the behavioral tasks that we use in mice to assay depression just can’t capture the really complicated human.”
The Human Factor: Set, Setting, and Indigenous Context
The team points out that human psychedelic experiences depend heavily on “set and setting”, the psychological expectation, emotional state, and physical and interpersonal environment surrounding the session. Translating this subjective framework into rodent cages introduces significant confounding variables.
Dr. Andrea Gomez, a member of the Laguna Pueblo tribe whose lab investigates RNA alternative splicing and synaptic plasticity, emphasized the mismatch between traditional usage and reductionist rodent models.
“In traditional medicinal use of psychedelics, a person experiencing the drug is within a community and they go back to their community after the trip and interact. The healing part is connected to the integration part,” Gomez said. “How do we fit an Indigenous methodology that has worked for thousands of years to a Western type of structure? How do you model the hallucinogenic aspects of a trip in an animal that is separated from humans by millions of years of evolution?”
Through fine-grained statistical modeling, the consortium analyzed subtle environmental variables across the five sites, including animal vendor sourcing, handler biological sex, handling habituation protocols, enclosure dimensions, and testing time-of-day. Ultimately, none of these environmental differences accounted for the absence of persistent behavioral changes across the aggregate dataset.
Refocusing the Translational Pipeline
The researchers argue that uncovering the lack of 24-hour behavioral shifts in mice is not an indictment of psilocybin’s therapeutic utility in humans, but an essential recalibration for basic neuroscience.
By identifying which animal phenotypes are genuinely reproducible, such as acute fear suppression, scientists can focus on mapping the precise prefrontal and subcortical microcircuits mediating those specific actions.
“The broader story is the importance of building reproducibility into psychedelic research from the outset,” concluded Dr. Stephan Lammel. “Mouse studies inform our understanding of how psychedelics might work therapeutically, so establishing which findings hold up across labs is essential. Our collaboration across Berkeley, UCSF and Stanford puts this principle into practice and offers a model that could extend to other areas of basic research.”
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this psychopharmacology Research:
- Media Contact: Robert Sanders
- Source: University of California – Berkeley
- Image Credit: Image credited to Neuroscience News
- Original Research is Open Access: Nature Neuroscience (Nov 2, 2026). “A multi-institutional investigation of psilocybin’s effects on mouse behavior.” Authors: Odilia D. Lu, Katrina White, Kendall B. Raymond, Christine Liu, Alexandra S. Klein, Nathaniel Green, Sam Vaillancourt, Austin J. Gallagher, Lena Shindy, Alyssa Li, Kira E. Wallquist, Ruoxian Li, Mila Zou, Austen B. Casey, Natalie Perez, Muhammad Asim, Setareh Metanat, Kelsey R. Logas, Vivan Chhaya, Alexander S. Enos, Ellie M. Ho, Lindsay P. Cameron, Matthew B. Pomrenze, Jason M. Tucciarone, Vikaas S. Sohal, Mazen A. Kheirbek, Andrea M. Gomez, Stephan Lammel, Boris D. Heifets & Robert C. Malenka.
- DOI: 10.1038/s41593-026-02500-z
Abstract
A multi-institutional investigation of psilocybin’s effects on mouse behavior
Studies reporting the effects of psychedelic drugs on mouse behavior are rapidly emerging. However, the reproducibility and reliability of these effects remain uncertain.
Here we implemented a multi-institutional collaborative approach to assess which effects of psilocybin on mouse behavior are robust and replicable.
Five independent laboratories performed the same experiments to test the acute and persistent effects of psilocybin (2 mg kg−1, intraperitoneally) on various behaviors. Psilocybin acutely increased anxiety- and avoidance-related behaviors and decreased fear expression in a robust and replicable manner.
Surprisingly, however, psilocybin did not have replicable effects 24 h after administration in terms of reducing anxiety- and depression-like behaviors or facilitating fear extinction learning. Additionally, we did not observe psilocybin-induced alterations in social preference or social reward learning.
Our characterization of psilocybin’s behavioral effects, using ~200 male and female mice per experiment across five laboratories, demonstrates several robust acute effects and suggests that some of psilocybin’s reported persistent effects in mice may be modest and/or inconsistent.
