Answer:
He might be having a hard time just because it looks good on the outside doesn't mean he's ok on the inside, but you never know he might just be doing it for the "fun" of it. You don't have to directly say it to him but it would be for the best to confront him and ask him genuinely why he is using dr*ugs. Maybe say something along the lines of hey why are you doing drugs? make sure he doesn't feel pressured or uncomfortable, tell him to be honest and that you can trust him.
Explanation: