Most times ppl r not the way they seem maybe ur brother started experimenting with those things back when he was at UV, trust me as introvert myself we know hw to hide n not to be noticed. Maybe he handled it well all those years especially if he was away from home different city back when he was at UV, thats more likely. Ofc this assumption is based on my experiencec, if ur not busy n the work doesn't demand that much mental work + if there is no direction in ur life if ur not planing to change the situation ur in considering ur not paid well or at least having better experience for ur future u will be hopeless n caught up in some circle of friends doing things u dont really thought of just following the "dudes" trying to make sense of the world. Try to have very honest talk with him dont be judgmental, if ur or acting like ur not he will sense it. be close n honest n try to be his friend then u will understand why he is doing all this or even suggest some tips but it takes time if is deep into it, maybe its just a phase but trying to know ur self really helps at least that worked for me........ U can only try he is a grown man he is making the choices.... Good luck!!