Psilocybin Extends Lifespan in Aged Mice and Delays Cellular Senescence

Psilocybin has attracted enormous clinical interest for psychiatric and neurodegenerative conditions, but its systemic and anti-aging effects have been essentially unexplored. This study provides the first experimental data suggesting psilocybin may be a geroprotective agent, operating through mechanisms that include senescence delay, telomere preservation, oxidative stress reduction, and SIRT1 upregulation.

For in vitro work, the team used a validated replicative senescence model with human fetal lung fibroblasts continuously treated with psilocin (the active metabolite of psilocybin) at 10 µM or 100 µM. At 10 µM, psilocin extended cellular lifespan by 29%; at 100 µM, by 57%. The higher dose also extended lifespan by 51% in adult human skin fibroblasts, confirming cross-cell-type generalizability. Psilocin-treated cells showed reduced β-galactosidase activity (a senescence marker), lower p21 and p16 (cell cycle arrest markers), higher PCNA and phospho-RB (proliferation markers), elevated SIRT1, reduced GADD45a (indicating less DNA damage), lower Nox4 (oxidant production), higher Nrf2 (antioxidant defense), and importantly, preserved telomere length compared to vehicle-treated age-matched cells. Critically, all treated cells eventually reached replicative senescence with no evidence of oncogenic transformation.

For the in vivo study, 19-month-old female C57BL/6J mice (equivalent to roughly 60–65 human years) received oral psilocybin at 5 mg/kg for the first month, then 15 mg/kg monthly for a total of 10 treatments. Psilocybin-treated mice showed 80% survival at study end versus 50% in vehicle controls (log-rank p = 0.014). Body weight loss was not significantly different between groups. Psilocybin-treated mice also displayed qualitative improvements in fur quality, including regrowth and reduced graying, consistent with phenotypic rejuvenation.

The authors propose that psilocybin's geroprotective effects may be mediated partly through 5-HT2A receptor agonism, which activates SIRT1-dependent antioxidant pathways, and potentially through epigenomic mechanisms such as chromatin remodeling and DNA methylation changes known from prior psychedelic research. The study explicitly supports the previously theoretical 'psilocybin-telomere hypothesis,' which linked psilocybin's broad clinical efficacy to its potential to slow biological aging.

Important caveats include the all-female, single-sex in vivo design, the relatively small sample sizes, the use of in vitro doses (10–100 µM) that may not directly translate to in vivo pharmacology, and the absence of cancer surveillance data in long-term treated animals. The study did not assess maximal lifespan extension or the impact of earlier intervention. Regulatory barriers around psilocybin's Schedule I status also continue to limit mechanistic follow-up research.