As far as i understand, psylocin and LSD have never been shown to be dangerous, in combination with any drug with possible exception to MAOI _maybe_. There are interactions that make it less intense and interactions that make it more intense. The only real danger is that you'll do something bad while in the state, not that the state will actually harm you.

So it's perfectly reasonable for someone to take a low dose of LSD while on antidepressants. The worst I've ever heard of occurring is that you just won't feel it at all. It's a targeted agonist of multiple serotonin receptors, i don't believe it actually releases any large flood of serotonin. Something like MDMA though _is_ very dangerous to take with SSRIs due to serotonin syndrome.

I've known many people to do psychedelics while on antidepressants and non of them have ever approached the levels of danger or concern that I've seen for people doing MDMA while not on anything else. The traditional psychedelics (LSD, shrooms) are remarkably safe and there's no reason to act like this person is being dumb or disingenuous for doing them in their circumstance. If you have research to the contrary I'd certainly welcome the opportunity to learn