Someone asked me last night to describe what my depression was like. It was interesting; except for sessions with my therapist I never had tried to put it in words to anyone.
I said: I found it hard to get out of bed in the morning. Sometimes I found it impossible to sleep at night. I lost interest in my work, in reading, in eating, in writing.
The worst part, though, was what my brain was doing. Or rather, not doing. I would stare at a computer screen for hours, berating myself for not doing anything constructive, then berating myself for wasting time berating myself. I would find myself confused and angry for being so stupid as to waste my own time and work, to spend days doing nothing and finishing nothing, but when I tried to do anything I would convince myself that it was such bad work that I could hardly bring myself to finish it.
I think this is what most studies of depression miss. Over time, it turns into a self reinforcing loop, a cycle that tears the sufferer apart.