I think people tend to put way too much weight on adaptationist explanations for things. Its much more likely that the mechanisms for depression are there to ha

I think people tend to put way too much weight on adaptationist explanations for things. Its much more likely that the mechanisms for depression are there to handle some other beneficial thing and that depression is just a side effect of it. One thing that highlights this sort of reasoning really well is genetic diseases. In some situations (cystic fibrosis, syckle cell anemia, etc) the mutated gene gives benefits as long as you are lucky enough to not get two copies of it, in which case you get a fatal disease instead.