Stress and its effect on the immune system

With it being almost the end of the semester and that much closer to finals, stress is something almost everyone is dealing with. Have you ever noticed that whenever you need to meet a deadline, a cold will always seem to start?

Doctors long ago confirmed that the connection between stress and health is real, but they haven’t been able to fully explain it. Now, in a new study, researchers say they’ve identified a specific biological process linking life stressors – such as money trouble or divorce – to an illness.

Most research in this area has focused on cortisol, the so-called stress hormone released by the adrenal glands when we feel threatened or anxious. One of cortisols jobs is to temporarily dampen the immune system, specifically the inflammatory response, in order to free up energy to deal with threats. This is useful if you happen to be attacked by a bear, but it also happens when you feel threatened by a deadline.

The fact that cortisol suppresses inflammation presents a puzzle: People who are chronically stressed, like college students, tend to have higher levels of cortisol. Yet the sneezing, sniffling and coughing of the average cold are actually caused by the inflammatory response to a virus, not the virus itself. So shouldn’t stress therefore prevent cold symptoms?

The authors of this new study have an answer: The key factor that influences a person’s vulnerability to illness appears to be the immune system’s sensitivity to cortisol, not a person’s cortisol levels. And the study suggests chronic stress may weaken the body’s responsiveness to cortisol, allowing the inflammation that causes cold symptoms to run wild.

“Stressed people’s immune cells become less sensitive to cortisol,” says lead author Sheldon Cohen, Ph.D., a professor of psychology at Carnegie Mellon University, in Pittsburgh. “They’re unable to regulate the inflammatory response, and therefore, when they’re exposed to a virus, they’re more likely to develop a cold.”

Cohen and his colleagues tested their theory in a pair of experiments, published this week in the Proceedings of the National Academy of Sciences. In the first, they interviewed 276 healthy men and women about the sources of psychological stress in their lives over the previous year, including unhappy work situations, long-term conflicts with family or friends, or legal or financial woes. And then they tried to get them sick.

While it isn’t a cure for the common cold, lowering your level of stress can help avoid getting sick at the worst possible time, when something important needs to get done.

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