Stress makes the common cold more miserable and harder to kick by letting inflammation linger, a new study found.
Men and women who had chronic stress caused by work woes or marital strife were more likely to develop persistent cold symptoms after inhaling the cold virus than their stress-free counterparts. The culprit: cortisol, a stress hormone that serves as the off switch for the body's inflammatory response.
"The symptoms of a cold are not caused directly by the virus, they're caused by the inflammatory response to the infection," said Sheldon Cohen, a professor of psychology at Carnegie Mellon University in Pittsburgh and lead author of the study published today in the Proceedings of the National Academy of Sciences. "You want to produce enough of inflammation to fight off the infection, but not so much that you experience cold symptoms."
With chronic stress, cortisol is overproduced, and the immune system becomes resistant. In the absence of the off switch, inflammation lingers long after the cold virus is gone.
"You have people whose immune cells are not responding to cortisol and, at the same time, they're exposed to a virus system creating an inflammatory response. But the body doesn't have the mechanism that allows it to turn off the inflammatory response, which manifests as cold symptoms," said Cohen.
The finding sheds light on the elusive connection between emotional stress and physical symptoms.
"There's quite a bit of evidence that people under chronic, enduring stressors, when exposed to a virus, are more likely to develop a cold than people who aren't suffering stress. What we didn't really know is how stress gets under the skin, so to speak, to influence these diseases," said Cohen. "This really suggests that inflammatory diseases, like asthma, autoimmune disease, cardiovascular disease, would most likely be affected by stress."
Dr. Redford Williams, director of Duke University's Behavioral Medicine Research Center, said the study adds weight to stress management as a medical treatment.
"This provides a new mechanism for how stress plays a role in all kinds of diseases, not just colds but also coronary artery disease," he said. "And there's evidence that coping skills training can really reduce both the psychological and biological manifestations of stress."
Williams said the link between stress and disease has long been recognized, but only recently have researchers begun to tease out how stress makes the body more vulnerable to diseases.
"We have to focus on the biological pathways between stress and disease," he said. "As we learn more about that, I think we'll be able to design interventions that are more likely to be effective. We will enter an era of personalized medicine where we're able to prevent the disease from ever starting."