But was your friend's son pre-disposed to psychosis anyway?
Probabaly, yes. But no one knew. He didn't have a history of mental illness. That's the whole point.
Typical age of onset for mental conditions such as schizophrenia is early to mid twenties. The person, usually male, can be afflicted suddenly, and marijuana can be the catalyst.
So what I'm saying, is that this young man in the article,(though I don't know for sure) could very well have seemed 'normal' to everyone and then had a psychotic episode brought on by the pot.
It has been seen a number of times before.