[roguecoder]

I saw an interesting theory that "depression" is a set of signals pointing us to solve a problem: it lets us skip eating, because we don't feel hunger, and sleep, because we have insomnia, and other things we would otherwise want to do, since we have trouble caring about anything. It lets us think about one problem for a long time without being distracted, because we ruminate on it. We don't get discouraged by failures, because we don't care about anything the way we usually would.

It's sort of like a computer down-clocking when it is overheating.

The problem comes because there are a lot of different mechanisms that can trigger that set of circuitry. So when depression is triggered by grief over a death, for example, no amount of time and energy and not eating is going to bring them back. And sometimes it wasn't kicked off by anything in particular at all, or our brain gets stuck in that mode even after whatever kicked it off gets solved. At that point there is a tendency to look for a problem that is so overwhelming it can explain why we ought to stay in that mode, whether or not it is being useful to us.

I like this explanation because it matches my experience. Personally my depression was because I had undiagnosed ADHD: I was constantly grieving my inability to accomplish things I wanted to do and enjoyed for no conceivable reason. And in this case it even actually kind of did its job: I stuck with the medical profession through an unbelievably long journey to getting that diagnosis and the easy and extremely effective treatment, because I had trouble caring about anything including my repeated failures to get any help at all from what medical professionals offered.