If you guys are such close friends you need to TALK TO HIM.
Communication is so essential!
I recently got really close with one of my guy friends. After about a week he told me he had a crush on me. I have a boyfriend (they go to the same school) so I was a little surprised. But we just talked it out and everything is fine now. We even make jokes about it. Yeah, so he still likes me, but it will pass
Umm... your mental condition queries could be relevant because of the fact he has done drugs. They do mess with your head so maybe if his behavior gets worse you should take him to a doctor. Or research it for further information.
xx