Is it possible to have depression for 10 years continuously?

Since the beginning of teenage my friend told me that he has been feeling hopeless and tired. This person thought it was just being a teenager, or just pure laziness, and that feeling would go over later. But it didn't. 10 years later and it just got worse to the point that this guy can't bare anymore. Feels that he is too old already and don't know what to do about it. He says that he could not finish University, all his relationships didn't work out and he usually likes to be left alone. Says that he just want the pain gone Yes he has been to a psychologist but apparently depression wasnt noticed, or he probably didn't show what he was really feeling, because most of the people he knows never did, just thought that he was lazy. Anyways, I guess that hes always wearing this mask because for being a man, he has to be strong and the alpha-male kind, if you know what I mean. Well is it really possible to have depression for 10 years? Or maybe the pain got too worse that now he can call that depression? Apparently recently it was hard for him to accept that he has an issue, now he does and is looking for help