Eye on Health: Professor studies your immune system on stress

As the semester winds down, the stress may be building up. And though you have no time to get sick, it may seem almost inevitable — a little tickle in the back of your throat, perhaps, or a nagging headache or achy joints warning of an impending illness.

Why does stress wear your body down? Christopher Coe, a professor of psychology and director of the Harlow Center for Biological Psychology, has spent more than two decades studying the links between stress and the immune system.

“Stress begins with a perception of the world as demanding, threatening, requiring an internal adjustment to deal with the demands of the situation,” he says.

That internal adjustment is the stress response, a physiological shift from the status quo of growth and general maintenance to a primed, energetic state, ready to respond to an external stimulus. This “fight or flight” response is a holdover from the days when the greatest challenges facing our ancestors were physical, he says, and despite our modern lifestyles, our bodies are still trapped in the Stone Age.

“It was very adaptive when we were fighting lions,” Coe says. “But we also do it for work stress, or when we’re having an argument with our husband or wife. We activate that same physiology because the body doesn’t make the distinction whether you’re running, fighting or stressed out at work.”

The stress response triggers a sort of triage approach, deferring longer-term needs like health, immunity and reproduction in favor of immediate support for the brain and muscles. Stored sugar and fat reserves are mobilized to the blood stream to provide quick energy, and protein synthesis and cell growth are temporarily suspended.

Inflammatory responses ratchet up in anticipation of possible wounds, but much of the rest of the immune system, including the parts that make antibodies and fight off infection, dials down to free up resources.

For example, Coe has found that an important immune function, the “natural killer” cells that patrol the body to search out and destroy infections, dropped by roughly half in students during finals week. In other studies, he showed that asthmatics mounted a larger allergic reaction against inhaled irritants during exam week than during nonexam times.

Stress can also lead to reactivation of latent infections, such as the herpes virus responsible for cold sores. Coe is currently working to understand how factors such as gender, social support and depression can influence stress-induced immunity changes in different people.

The stress response is well adapted to cope with acute, short-term situations — which may be why people often get sick right after, rather than during, a stressful period — and immune function and other suppressed systems will typically rebound once the stressor is over. (It takes about two weeks in students post-exams, but much longer as we age.) However, prolonged stress over months or even years can cause lasting physiological changes and has been linked to heart disease, obesity and diabetes.

It’s ideal to minimize the stress in your life, but if you do start to feel a suspicious tickle in your throat in the midst of life’s craziness, just remember that the stress response worked well enough for our ancestors that we’ve made it to where we are today. And be glad that you aren’t fighting lions.