What are the physical signs of drug abuse?

My friend recently moved in with me and I’m worried he may be on something. He’s always fidgety, talks a lot about nothing, his eyes are always dilated, and when he goes into the bathroom he’s in there for quite a while. When he comes back out he says he’s having stomach troubles but (and I know this might seem nasty) it never smells so I’m thinking unless his business smells like roses he’s doing something else. Am I just being paranoid?

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