[powaoxal] Depression feedback cycle and evolution

If you're sad, no one wants to be friends with you.  If no one wants to be friends with you, you'll become more sad.  Surely this feedback cycle is not new, not just a feature of modern society.

Some amount of those depressed people will commit suicide and not pass along their genes to the next generation.  Or, they will seek out sexual intercourse less frequently, or they will be less desirable, so potential partners will seek them out less frequently.  Or, as social outcasts, their children will receive less support so be less likely to survive until maturity.  Evolution is very sensitive to these effects, especially if given thousands of generations.  So it is very mysterious why this feedback cycle exists, and exists so strongly.

Previously, hypothesizing bipolar.