Weed and schizophrenia?

Hello,
I have a friend who's schizophrenic. He doesn't drink at all and stays away from weed for he believes his state could improve if he stopped doing these things. But recently I've visited him and saw he was very obviously stoned. He had difficulties with focusing on the conversation and was speaking in a confusing way. I know him long enough to see when it's the medication and when it's something else. Not only was it visible in his face but his niece said she was able to recognize the weed smell very well.
He used to say he enjoyed smoking weed when being a teenager but that it was all past because of his illness. Although I do think it was just an exception - he has so little money he can't afford anything and definitely not weed - the fact he used to smoke it so much in the past is frightening to me. It was most probably given to him by one of the stupid villagers. But it worries me a lot, I'm afraid he could start a new addiction and make the already shady looking situation much, much worse.
What do you think I should do? Should I speak about it with him? What should I say? I know I'm not a part of his family but his family doesn't care about him much, so they probably won't give a thing about this. Not mentioning I'd call myself the only close friend he has and as I care about him as well, seeing him like that makes me feel worse than seeing the dulling effect of his medication.
Thanks for any advice in advance!
B.

Hello Fififjonka

Anyone with schizophrenia, who is not taking medically prescribed drugs that have been individually attuned to their condition by a competent physician, is probably playing with neurological fire. Although medical marijuana can be such a medication, If it were me I would have first consulted with one or more of my doctors.

As far as what you have seen, all you can do is slip into the conversation, "you know, you make a lot more sense when you aren't stoned," or, "man you really shouldn't smoke weed."

Offer your advice in a sincere and compassionate way as a friend, not top-down.

Of course, what he does with your advice will be up to him .