Interesting articles I’ve found here referenced from discussion on Twitter. Does depression have a heritable advantage? Interestingly, some of the genes that cause depression also seem to have an effect on strengthening the effectiveness of the immune system. In the old days, any cuts or wounds would almost certainly result in infection, and without modern medicine, that would very likely result in death. But, the alterations in the immune system caused by the same genes that caused depression strengthened the body’s ability to fight off infections, if not also causing changes in the brain that would completely avoid situations that would likely result in infection.
In modern times, however, infection is not at all an issue to treat with modern medicine, so the tables are turned.
20200221/https://www.theatlantic.com/health/archive/2012/10/the-evolutionary-advantage-of-depression/263124/
20200221/https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2989690/