Basically raises your risk for serotonin syndrome. This is particularly close-to-home for me because I had a close friend who was taking an SSRI who began using psychedelics of all sorts (psilocybin mushrooms, LSD, MDMA, etc) & i watched her fry her brain. One time on a trip, she couldn’t stop saying the same thing over, & over, & over, & over again. She didn’t know who she was. This is coming from someone who has used psych’s before; they’re a beautiful time, but not was SSRI’s. Don’t take the risk.
Update, I’m having a hard time finding anything else. I think this article does a good job explaining the science behind why the risk of serotonin syndrome is raised when you combine psychedelics with SSRI’s. Please be careful friend & do not combine these two classes of substances