If you advise people predisposed to psychosis to stay away from LSD, you should also advise them to stay away from sex and any and all other intensely emotional experiences.

That said, there's always a risk to doing anything. People choose to engage in risky behaviors every day. You take a risk by moving your butt out of your chair. You certainly take a pretty big risk to your mental and physical well-being by riding in or driving a car (it risks your mental well-being due to the possibility of brain injury in an accident). Yet people do it all the time. Often without giving it a second thought -- and if you point out the risk they're taking, they'll usually shrug it off.

Some people like to risk their lives by smoking tobacco, others by drinking alcohol, yet others by stuffing their face with junk food. For some the fun is in risking their lives skydiving, or scubadiving, or hang-gliding, or paragliding, or surfing, or spelunking, or swimming.

But you don't have to go to extremes to risk your life. Just hanging out at the local pub is risky (you could get injured or killed in a brawl). Climbing a ladder is risky. Crossing a street is risky.

But once the subject turns to drugs people start freaking out about the fact that you're taking a risk by doing them, as if taking risks was something only crazy homeless people and stunt-car drivers did, and not something they themselves did every day of their lives.