observable symptoms did. Most people develop schizophrenia in their early twenties. They deal with all kinds of internal mental problems before they start going into psychosis or talking to themselves or displaying other outwardly observable symptoms. It's very likely he's been going through all kinds of things that you were unaware of for a very long time. People like that frequently use cannabis to self medicate. I'd be careful blaming his mental health problems on his drug use. Unless you live inside his head it's impossible to know which started happening first