[kevinoid]

A significant effect is through opioid receptor activation, as demonstrated by Williams et al. <https://doi.org/10.1038/s41380-019-0503-4> by blocking the receptor with naltrexone, which attenuated the antisuicidality effects.

The Huberman Lab episode Ketamine: Benefits and Risks for Depression, PTSD & Neuroplasticity <https://www.hubermanlab.com/episode/ketamine-benefits-and-ri...> and the referenced journal articles (including the above) have a lot of detail on it.