Emo

An emotionally unstable person. They don't have to wear black or cut themselves. Those are just stereotypes. They can be your next store neighbor and you would probably never know. Mostly, they are emo, because of bipolar issues and nothing seems to make them happy. Even Marilyn Monroe was emo.

That girl must be emo, because she always looks so sad. (I don't know, I had to fill in the example!)