It's not about tattoos, or piercings or dressing up. I have no tattoos or piercings but I dress very bold.

I think one could tell somebody has issues (that are not in remission) by their possure and general appearance and behavior. I mean, if you are twitchy and jumpy and look around constantly... there might be something going on. If you cannot control your reactions to normal situations... things like that. Or if you are extremelly umkempt. Otherwise, you cannot really tell.

Actually, eyes might be a give away. Dead eyes. Crazed "not fully there" look.