To evaluate the impact of psilocybin on longevity in vivo, aged (19 month) female mice were treated with vehicle [vehicle is what the psilocybin was suspended in for injection] or psilocybin [actually vehicle + psilocybin] once/month for 10 months; mice were initially given a low-dose (5 mg/kg) for the first treatment followed monthly high-dose (15 mg/kg) treatment for a total of 10 treatments. We elected to utilize 19-month old mice, which is roughly equivalent to 60–65 human years, in order to evaluate its therapeutic potential as a clinically-relevant anti-aging intervention.

Within 30 min post-treatment, mice exhibited increased head-twitch response, which is a well-established behavioral indicator of hallucinogenic impacts of psilocybin in mice. Both psilocybin and vehicle groups exhibited some loss in body weight from the start to end of the treatment protocol, however weight loss was not significantly different in vehicle vs. psilocybin-treated mice. Notably, psilocybin treated mice demonstrated significantly higher survival (80%), compared to vehicle (50%).

Although not quantitatively measured, psilocybin-treated mice exhibited phenotypic improvements in overall fur quality, including hair growth and reductions in white hair compared to vehicle-treated mice.

In summary, we provide the first experimental evidence demonstrating that psilocybin treatment can enhance survival in aged mice.

So, caveats:

This is the first study; while further studies may show a similar result, we won't know for sure until they are completed. This could be a fluke. This was neither a double blind nor a placebo study; it is possible things like researcher impacts could influence the outcomes.
This was neither a double blind nor a placebo study; it is possible things like researcher impacts could influence the outcomes.
Typical doses for psilocybin are 0.2–0.4 mg/kg in therapeutic settings, 4mg/kg for microdosing, to up to 20 mg/kg to be legitimately tripping; like the mice, if you use this regimen you will need to set aside a day to be tripping once a month, and after 10 months take a heroic dose and have a really big trip. Not impossible to arrange for many people, but this is not a regimen you can do while completely going about your regular day-to-day.

TLDR: Promising results in an under studies area. More studies are required to confirm results. Following this regimen will cause a non-trivial disruption in your monthly routine.