i bet you if a statician studied marijuana with psychological disorders, there would be a fairly strong correlation between marijuana and and those disorders. That is to say, there is probably a larger distribution of mental disorders in cannabis users then there is in non-cannabis users. I wouldn't be shocked if i heard that this is the case. Of course, this is only a hyptothesis, and i neither have the time, willpower, or resources to run a regression analysis (although, i do know how to run regression analyses)