Depression.

[All_That_Chaz]

Something that has always bothered me about the evolution of man is that with the development of an advanced brain also came the onset of a throng of mental diseases, defects, or other ailments. Why would humanity evolve to feel things such as depression? It makes us lethargic, despondent, and uncaring about what happens to the self or others. I can't imagine any beneficial aspects of these feelings/neural deficiencies. Why do we have them? Is it just a note that we are still developing as a species? Or perhaps is there some vestigal reason behind a need for these problems?

I'm going to assume evolution is correct for the purposes of this topic, and there are plenty of other threads on that, so please stay on topic here.