[Crani]

Age is relative, most teens, do to hormonal related problems, which can be aggravated by the environment they live in, they don't get what's the point of living (I don't know either, but trying to find it is part of the game, so I'm gonna keep playing it) and just chose to end it, because they can't take a little pressure, because they passed there childhood doing nothing and know a small problem appears and they freak out.
As for depression, everybody is intituled to have them once in a while and I won't blame them, you don't choice when it's going to happen, as long as they don't fuck things up for another person.