I have tried LSD a few times and had nothing but positive experiences. My wife, however, tried it once and had a bad trip. She was convinced I was going to murder her (obviously everything I did further proved that point) and everything was scary for her. She was afraid of large trees in a kind of "raises my anxiety baseline" kind of way for about a year after the trip. But, the experience wore off, and she's fine now. She believes that it's possible that the experience contributed to her being a more anxious person now, but that's conflated with all kinds of things like marrying me and changing careers and having greater responsibility for those around her.

I don't think it's as big a risk as you seem to think. The people who I have met who have had bad trips did not see lasting side effects, though they did take a while to wear off.

I'm sure someone else will post it, but if this is something you genuinely want to know more about, read "How to Change Your Mind".