Im not defending anything here, mainly because i have started smoking a little more frequently for myself (maybe once or twice a year) but i remember in those D.A.R.E. lectures that they called pot the "gateway drug." Im not sure if its necessarily true, but it is something that stuck with me all through school. If they are right and pot is a "gateway" drug, then that could be why they are saying psychosis goes up (lead the attack on the original source)