As a medical student I spent my psych rotation with a psychologist that was a fan of 'evolutionary psychology' His brief was that depression is evolutionary, a

As a medical student I spent my psych rotation with a psychologist that was a fan of 'evolutionary psychology' His brief was that depression is evolutionary, and has an evolutionary function. In his view, depression is the result of 'loosing'. His example was a certain species of insect, I forget which now, which challenges another male to a display/fight. The looser not only turns bright orange in response to the stress hormone cascade released after loosing, but also stops eating and more than 50% die from starvation before recovering. How is this an adaptation? Well, the stress response reinforces hierarchy, and maintains group cohesion by providing a mechanism for 'shunning', both by other group members and by the individual theirselves. He was a big fan of Robert Trivers, an evolutionary psychiatrist who has written much on 'the evolution of reciprocal altruism'. Now the fact that depression may have a strong evolutionary cause is of course maladaptive in our modern world where we would like all people to enjoy happiness and be productive members of society.