Depression is so detrimental to good health, it’s hard to believe that the human body hasn’t found a way, through evolution and adaptation, to eliminate it. Unless, of course, it serves a purpose. If depressionitself is an evolutionary adaptation, what advantages might be found in the depressive state?
Andrew Miller, MD, Emory University, and his colleague Charles Raison, MD, University of Arizona took a closer look at the evolution of depression. Their new study looks at the depression-immuno-activation combination. These scientists propose that genetic variations that promote depression are linked to behavioral responses that fight infection. The two are encoded on the same genetic structure making genetic markers for inflammation a predictor of futuredepression.
Researchers have long acknowledged a link between depression and inflammation. People with depressive symptoms tend to have higher levels of inflammation regardless of whether or not an infection is present.
Fever, fatigue/inactivity, social avoidance and anorexia are all adaptive behaviors, symptomatic of depression, that help to contain infection and contagion. Depression developed from this and is now hard wired to the immuno response.
Even stress can be seen as a byproduct of immune-activation as the body prepares for infection or anticipates a wound. Sleeplessness caused by illness or the need to stay vigilant protecting oneself from predators would cause an activation of depression and immune system. After centuries, the two are now inextricably linked.
And it could be that medications meant to treat auto-immune diseases could also treat depression. Miller and Raison are studying this potential now.