The ironic thing is there was a guy in my inner circle who did the least amount of drugs in general, went totally schitzophrenic, now homeless and struggling to battle his mental and emotional demons. This guy didn't smoke a lot of weed, maybe did other drugs a total of 3 times.

I witnessed his decay slowly through a 2 year period. The changes were subtle, until one day, you realized he was talking to himself, making strange noises constantly, you notice his anxiety, and see the anger inside of him. As much as I care about this kat, I can't stand to be around him for more than 1/2 an hour because he's that crazy, and I'm kinda afraid he would swing at me randomly.

Bi-Polar varies to degrees, but it sounds like it's the only issue your brother has. A lot of these personality traits cross each other. I know my share of bi-polar people (trust me, I attract the weirdest people,) and all of them had it before they even smoked weed, life-long issue.

Get a 2nd opinion. With these psychatrists, most of them are wrong. You have to talk to at least 5 different ones before you can get a glimpse of your personality disorders.