MONDAY, April 2, 2012 (Health.com) — Most of us know from experience that stress weakens our immune system. Colds always seem to strike when we’re overworked or emotionally exhausted, as do eczema flare-ups, headaches, and myriad other health problems.
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, in this case the common cold.
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 cortisol’s jobs is to temporarily dampen the immune system, and specifically the inflammatory response, in order to free up energy to deal with threats.
The fact that cortisol suppresses inflammation presents a puzzle: People who are chronically stressed 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. Shouldn’t stress therefore prevent cold symptoms?
The authors of the 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 his or her cortisol levels per se. And chronic stress, the study suggests, may weaken the body’s responsiveness to the hormone, 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.
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