This is a TED talk that was linked to me earlier today.

The opposite of depression is not happiness, but vitality, and it was vitality that seemed to seep away from me in that moment. Everything there was to do seemed like too much work. I would come home and I would see the red light flashing on my answering machine, and instead of being thrilled to hear from my friends, I would think, "What a lot of people that is to have to call back." Or I would decide I should have lunch, and then I would think, but I'd have to get the food out and put it on a plate and cut it up and chew it and swallow it, and it felt to me like the Stations of the Cross.

And one of the things that often gets lost in discussions of depression is that you know it's ridiculous. You know it's ridiculous while you're experiencing it. You know that most people manage to listen to their messages and eat lunch and organize themselves to take a shower and go out the front door and that it's not a big deal, and yet you are nonetheless in its grip and you are unable to figure out any way around it.

He talks a lot about his travels and talking to people with depression, and what treatment means. He speaks frankly about a lot of things - about the perception of depression as an illness. I think it's worth the listen.