Depression and Evolution - Page 2
To put this in perspective, humans as we would recognize them have been eking out a life for themselves for around one to two hundred-thousand years in total depending on our best estimates. During this time in the human story life expectancies were incredibly low by our standards. Infections that we can easily treat with modern medicine were one of the main causes of death for our ancestors. Looking at humanity from this vantage point we can begin to understand why depression could have been a positive evolutionary trait for so much of our shared history.
Previous studies have shown that those who are struggling with depression appear to have an over-active immune system. This is the case even if the depressed is not fighting any form of infection. In the past, the ability to survive infections would play a key role in passing on ones genes to the next generation. If we tie this knowledge in with how we know stress can bring on a depressive episode a clear picture emerges. A disease or infection strikes a group of people in a pre-agricultural human tribe. This in turn causes stress among its members. This stress brings on depression, which as a result sends our immune system into overdrive hence increasing our chances of survival from the disease or infection.
Professor Miller explains, “Most of the genetic variations that have been linked to depression turn out to affect the function of the immune system. This led us to rethink why depression seems to stay embedded in the genome. The basic idea is that depression and the genes that promote it were very adaptive for helping people –especially young children- not die of infection in the ancestral environment.”
When stated in this manner, the evolutionary reasons for depression appear to make sense. Yet despite how convincing it may sound, at the moment this remains only a theory. In the meantime those people who unfortunately struggle with depression must be content in the knowledge that many people are currently on the case. It may be a while before we solve the riddle of depression, if that is even possible, but the more we understand the better treatments we can provide. Finally I would like to add that if you or someone you know are struggling with depression do not suffer in silence, please seek out someone who can help.