One of my close friends kind of went crazy after a bad trip at his dad's place. I was there, nothing bad really happened, just a few of us tripping blastin' some tunes all night.
His father was in another part of the house so he didn't even saw us but my friend kept thinking about that and really affected him (he was dealing with some other things related to his father and stuff too at the time, nothing super serious).
He used to be a big stonner at the time and after that night he stopped smoking weed and using other drugs except maybe a little alcohol. He had to stop everything because he was having symtoms of HPPD and general anxiety. That was almost a year ago and I think he is alright now (haven't seen him in some time but we talked not too long ago).
I think it ended up being a good thing for him because he had the opportinity to change some things in his life, he is still sober as well.
Had some other friend who also went "crazy", in another way though. He changed A LOT, he now believes we were slaved by some aliens millions of years ago and other things like that, it's too long to explain but it's something like what the scientologists believe. He dropped college and started going to meditation sessions instead.