Anecdotally, I think hallucinogen just highlighted mental issues that were already there. I also know some really smart people who have done their share of it with no problem (that i can see). If I could go back in time, i'd do it all again. We, as humans, were pretty open about all this not too long ago. I am happy to see a small number never stopped and psychonauts [4] though not always scientific, have kept exploring and bringing back ideas and experiences for these alternate states of reality.
Tangentially, Carlos Castaneda's [5] books were some of the best i've read and would recommend it to people.
[0] https://en.wikipedia.org/wiki/Psilocybin#History
[1] https://www.newscientist.com/article/mg20928025-400-earliest...
[2] https://www.vice.com/en_us/article/yvqqpj/psilocybin-the-mus...
[3] https://en.wikipedia.org/wiki/List_of_entheogenic/hallucinog...