As someone who is related to a neurologist... let me shed some light on this.
Believe it or not, Marijuana can and has done this to people. But here's the catch. 99.5 percent of us can enjoy marijuana. However, in people who have developed or shown symptoms of schizophrenia can be turned into Axe Crazy Maniac's. This is due to the THC's major role in acting in the same area of the brain that coordinates Schizo episodes, meaning the THC can be a catalyst to a major meltdown... like this.
Dont get me wrong I have nothing against mary J. This is literally a 100,000 to 1 kind of case. But... you wont hear the politicians saying that. Also, look up the movie Reefer Madness. A 1950's propoganda movie about weed. Its so off base with reality its almost funny.