Depression, good or bad?

Scientific American has an article that raises the question of whether depression is a malfunction or an adaptation. People can suffer because of depression and even become impaired in some ways, but this article argues that it serves the purpose of focusing one's mental energy on some critical problem. This process is called rumination.

We all get depressed from time to time. I certainly do, and I don't like it. I can't think of anything else except what's bothering me. But as the article suggests, I can come out of it quickly when I have a solution to the problem.

I recall often when I worked on a computer problem — not exactly the same thing as depression, I know — my attention would be extremely focused but I failed to see the answer. I could not stop thinking about it. Sometimes I would just go to bed, but when I woke up in the morning, I would immediately see the answer.