Five Labs Ran the Same Psilocybin Experiments in Mice. The Lasting Effects Didn't Hold Up.
Five labs across UC Berkeley, UCSF and Stanford ran the same psilocybin experiments on mice in parallel, using matched protocols, and published the results together in Nature Neuroscience this week. The study design was proposed by Stanford's Robert Malenka. The labs were led by Stephan Lammel and Andrea Gomez at Berkeley, Vikaas Sohal and Mazen Kheirbek at UCSF, and Boris Heifets at Stanford. The acute effects replicated everywhere. At 2 mg/kg, every lab saw the head twitch that researchers use as a marker of psychedelic activity in mice. Every lab also saw a spike in anxiety and avoidance 10 minutes after the dose, along with reduced fear expression.
The effects that drive much of the therapeutic interest did not replicate. Twenty-four hours after a single dose, the labs found no consistent reduction in anxiety- or depression-like behavior, no change in fear or social behavior, and no sign that psilocybin reopens a "critical period" for social reward learning in adult mice, a widely cited earlier finding. Two labs did see an effect on one of two standard antidepressant assays, which the authors attribute more to the assay's limits than to the drug. Co-first author Odilia Lu, a Berkeley doctoral student, called the lasting effects "modest, if anything," and cautioned that mouse tasks "just can't capture the really complicated human." Sohal put the stakes plainly: "if the hype around psychedelics outruns the science, there will be adverse outcomes."
This is a mouse study, and it doesn't overturn the human Phase 3 data now in front of the FDA. It does weaken the animal evidence often cited as the mechanism, and it shows that single-lab results deserve less weight than they get. It lands a week after a JAMA Network Open review found media coverage of psilocybin routinely outpaces the evidence. Robert Sanders wrote it up for Berkeley News, and STAT's Readout also covered it. Our intelligence hub tracks how the research base behind each compound is holding up.