There's as much evidence that THC (synthetic, administered orally) helps reduce schizophrenia symptoms and patients manage their symptoms ( Rockland Psychiatric Center, New York, & the New York University School of Medicine, 2009), as there is that it can contribute to producing schizophrenic-like behavior. NOTE. Not cause schizophrenia itself. Schizophrenia is almost universally considered a genetic condition, albeit one that is highly susceptible to being triggered/made worse by outside factors, such as drug use.
It's more likely your friend's son had some underlying issue (generally, genetically) that might have been triggered by THC consumption, particularly if that THC was especially potent.
Your buddy would be better off getting a thorough psychiatric workup done on his son and, needs to try and stop looking for boogey monsters that made this happen. If his boy is indeed paranoid schizophrenic, it would not have been caused by the THC, but could easily have been triggered into developing earlier ... but it's likely the boy would have mentally degenerated in any event: it was just a matter of time.
Hope that helps in some way. I can PM you a bunch of articles to read if you'd like.
I wish your friend and his son all the best for the future. They have a hard road ahead of them.
