im bipolar, which was diagnosed after ( about a year later) marijuana induced psychosis, it happened because a hit for me would be cashing the bong in a deep single rip and doing it in excess of 20 times a day, at one point i didnt sleep, then i didnt eat, thought people were vampiric etc.

ive been off it for 4 months, i dont miss it because the normal good feeling high i no longer recieve instead i feel uncomfortable in my body and overly paranoid..
its like my body evolved to give me signals upon getting high that it doesnt like it..

in retrospect i smoked too much in my life...binge drank too much at that also when i recently turned 21 in april..its been 4 months without mary and alc...the only thing i do now is cigs..

weed psycho. is real, but rare, and you need to reaaaallly be over doing it and other lifestyle factors greatly come in to play when it comes to ones mental state.