So there was this article in the New York Times Sunday Magazine last weekend (I pretend that I still live in NYC by reading the Times every day online) about scientists trying to find the evolutionary reason why depression is so common, and that its persistence might be due to some kind of beneficial role depression could play in our lives. Here is a link to the article "Depression's Upside". A psychiatrist and an evolutionary psychologist walk into a bar...oops, wrong start,..these guys brainstorm on depression and speculate that the dominate thought process of depression, 'rumination', has a positive impact on the brain - it helps one focus on one's problem(s) and think oneself out of a bad situation or cope with stressful conditions.
Depression is a broad term under which one can find all sorts of variations. To me, their theory, though comforting in a way, seems to be another 'lite' version of depression romanticized. The article gives anecdotal examples from clinical setting (ie normal depressive people in sad life situations) and, more of a leap, from literature and other 'creative' backgrounds (ie Darwin, David Foster Wallace). The link between depression and creative impulses has been brought up before. The idea that creative types are productive and inspired to do great things because of a depressive episode is unconvincing to me. It is more a credit to a person's drive and creativity if he or she could work in spite of a depressive episode. On the whole, depression is a low-functioning condition - not only can't one get out of bed, usually the thought process, while ruminative, is not complex and problem solving. Mostly it's a repetitious, vicious cycle of painful thoughts eventually immobilizing the individual.
The art process is significantly slowed down, stymied, possibly even reversed, during depression. If any work is done it is immediately destroyed during outbursts of severe self-criticism. Frustration, self-doubt and anger are not conducive to creation. Maybe the link between depression and creativity/productivity can be made with manic depression (aka bi-polar), as energy and drive can be found during a bout of mania. Or when depression lifts, energy and inspiration return (plus the drive to make up for the time lost to the depression).