Mystery,
You will never know what to do. Please believe me when I say that. Your teenager may be your flesh and blood but you do not know. It sounds like he is not depressed, though, he is just in "a depression", LOL! I'm not laughing at you, I'm just laughing at the lack of understanding here.
Lots of people go through depressions. Most teenagers do. I would say that your teenager is just about 100 percent normal. I'm probably talking about something very different here. Clinical Depression.