Five mouse labs replicate psilocybin's acute fear and open-field effects, but persistent behavioral effects fail to replicate consistently

A coordinated study across five laboratories found that a single 2 mg/kg dose of psilocybin reliably changed acute mouse behavior: animals showed more head twitches, spent less time in the center of an open field, and expressed less fear during memory retrieval. Effects measured a day or more later, including antidepressant-like, anxiolytic, fear-extinction and social-reward outcomes, did not replicate consistently, even in chronically stressed mice. The study used about 200 mice per experiment, standardized strain, dose and protocols, but shared a drug supply, vendor and analysis scripts, and did not preregister or report a sample-size calculation. Its conclusions are limited to one dose, strain, route and timing, with no human outcomes tested. Smaller or differently timed effects remain possible.