steve1

It's well known that there are substances which can cause a schizophrenic break. Amphetamines, or crank, are a classical example of it. It's well known in the psychiatric literature. Massive doses of male hormones often used by bodybuilders can also do it. Regarding cannabis causing mental disorders, that's still being studied. It takes more than one scientific report to establish something as confirmed and very likely the case. IN the case of amphetamines, those are known to cause psychosis, which might be temporary or not. Cannabis is not confirmed to do the same, but it could. However, more time & study are needed. As far as genetic predispositions to schizophrenia, only paranoid schizophrenia has a genetic cause, altho the gene has not yet been identified. Among identical twins, if one twin gets this form of schizophrenia, the odds are only 50% that the other will get it, too. Still, as the incidence of psychosis of this sort in the population is about 1/2%, it's 100 times the expected incidence, which is what established the condition as genetic. But why one twin gets the condition and the other does not, is not yet known. Real causes of schizophrenias are not well known at present. Much work is ongoing to determine more. Overall, cocaine, amphetamines and some other psychoactive substances use, such as LSD are associated with a considerable increases in death and disease, plus considerable bad social effects.