Ok, I'm gonna give this one a go cos I've had drug induced psychosis. I had it mildly after smoking too much weed, aparently I had this "wild" look in my eyes and acted like I was on speed the whole time, ie I'de smoke bongs and be speedy. But at the time it was not full blown psychosis, lots of things made it build up, being given acid in a drink etc. What set it off fully was have only 1/4 of a pill. So yes, I pill or less can cause drug induced psychosis, but it would seem to be if you have an underlying medical condition i.e depression, anxiety, depersenalisation, and the rest. I actually know one person who had one and only one joint and went mental 4 bout 3-4 months with mania and has bipolar as a result, the explanation however is that in his family there is a high likelie hood of mental illness occuring at that age that he was (20). Point being, for some, drug induced psychosis can take a long tiome to be reached and others it can be triggered like a light switch. I'm definetly not saying that all drug takers will get it, but my guess would be (and I may well be wrong) that quite a few have potential for developing it whether in absolutely mild for or full blown, but it would seem to be because of underlying med conditions....hope this helps even though it's a ramble....