Chronic stress in caregivers can create a genetic adaptation.

A recent study* by Gregory Miller, Ph.D., of the Department of Psychology, University of British Columbia, Vancouver, Canada, and colleagues, discovered that chronic stress may cause a person to develop a genetic marker or evolutionary adaptation to that stress. This genetic adaptation is the result of the chronic nature of the body’s reaction to the environmental stimulus (stressors). In other words, the stressed person develops a tolerance for the environmental stimulus – they adapt in such a way that they no longer react to stressors as they used to. Their threshold of tolerance has perhaps permanently risen – and in some people exposed to such chronic levels of stimulus, this adaptation has given rise to disease.

This evolutionary genetic adaptation to chronic stress has only recently been studied in any depth. Dr. Miller and associates investigated the genomes of chronically stressed individuals and compared them to people exposed to “normal” levels of daily stress. Their findings are summed up by Dr. Miller, “people have traditionally thought that higher cortisol is the reason that stress contributes to disease, but this work shows that, at least in caregivers, it’s actually the opposite – there’s too little cortisol signal being heard by the cells, rather than too much.”

Over time, the genome changes to accommodate the increased threshold. I’m no geneticist, but aren’t genetic markers passed on to later generations? I’ll bet today I’m experiencing some of my ancestors’ genetic markers to chronic stress. I’ve done enough genealogical research to know that some of my ancestors lived lives of chronic stress I can’t imagine enduring. Certainly each generation has its chronic stressors – from political unrest to chronic fear of warring neighboring tribes to living a life of servitude or slavery.

Those of us living today represent the genetic evolution of past periods of chronic stress in our ancestors. Those genetic markers we see in short-term (within a single lifetime) chronic stress are built upon our ancestors’ genetic markers for chronic stress. This would explain why some people can handle chronic stress better than others. Those whose ancestors experienced more chronic stress would tend to pass on genetic markers for higher levels of tolerance to chronic stress.

However, this genetic predisposition comes at an awful price. Higher levels of tolerance means higher levels of cortisol in the body – causing problems with the endocrine system such that, according to Dr. Miller, “[although] caregivers have similar cortisol levels as controls, their cells seem to be ‘hearing’ less of this signal. In other words, something goes awry in caregivers’ white blood cells so they are not able to ‘receive’ the signal from cortisol that tells them to shut down inflammation.”

It’s not the high levels of cortisol that cause inflammation (including weight management problems and disease), it is the body’s inability to react to the higher levels of cortisol. It’s a little like the first dance I attended as a youth. The music was so loud, we had to shout at each other in order to hear each other. When the dance was over and we got home, I greeted my dad in the hallway. “You don’t have to yell,” he told me. “I’m not yelling,” I screamed back at him. To me I was talking normally. To him it seemed I was yelling. After dealing with my own teenagers after dances of similarly loud music, I can attest that I no doubt was yelling at my dad but did not notice it because my level of awareness (tolerance) had risen.

Hope all that loud music I enjoyed as a teenager didn’t affect my genes. If my teenage children were any indication, however, my hope is lost…