Some people are susceptible for psychosis. LSD might give them the final push, turning them from the normal looking guy that sometimes say weird things to full-blown crazy.
I also know about a similar case in my social circle. An offbeat guy starts seeing demons after his first trip. Recovering in a mental institution ever since.
Yet I don't think LSD is to blame, it is just a trigger for a pre-existing underlying issue.
It doesn't matter either way - for all practical purposes, LSD causes psychosis to a small part of the population. Some of these people will develop psychosis without LSD, of course, but some will not.
Similarly, peanuts may kill some small part of the populations, fava beans a different part. They may die anyway independent of peanuts or fava beans. That's not a reason to ban them outright - rather, it's a reason to do the proper research to try to figure out who is susceptible and warn them.
