PITTSBURGH--Chronic stress, particularly stress brought on by enduring family strain or workplace pressures, makes us more susceptible to the common cold, according to a new study by Carnegie Mellon University psychologist Sheldon Cohen.
In a landmark New England Journal of Medicine article in 1991, Cohen provided evidence that stress was associated with increased risk of developing a cold.
In a new study that further defines the kinds of stress that reduce a body's ability to fight off infections, researchers took 276 healthy men and women between 18 to 55 years old and -- after assessing the stress in their lives, stress hormones and health practices such as smoking, alcohol consumption, diet, exercise, sleep -- exposed them to a virus that causes a common cold. Subjects were then monitored in quarantine for five days for the development of a cold. As in Cohen's previous studies, 40 percent became sick.
"Our interest is in whether the psychological and other measures we gather before exposing them to a virus predicts who is more susceptible -- in other words, who develops the illness," Cohen said. "In our earlier work, we found that questionnaires measuring how stressed people feel predicted who became ill. The greater the self-reported stress, the more the likelihood that they would develop a cold."
In this recent study, researchers replaced the stress questionnaires with an intensive stress interview, which allowed them to distinguish between acute (less than a month) and chronic (more than a month) stressors, and to assess the types of stressors that made people less resistant to infections like the common cold.
Cohen and his team found no increased susceptibility to colds in people who experienced episodes of stress lasting less than a month. But, he said that those who suffered long-term personal problems persisting for more than a month were 2.5 times as likely to become ill after exposure to the cold virus as people who weren't under a similar degree of stress.
"We found that chronic but not acute stressors placed people at risk for developing colds," Cohen said. "We also found that chronic stressors such as enduring social conflicts with family or friends and enduring problems at work, were responsible for more people catching colds."
He added that researchers are still unable to determine exactly how chronic stress makes people less resistant to infections like the common cold. Although several of the health practices--smoking, loss of sleep--and hormone measures also predicted susceptibility to illness, none could account for why stress was associated with a greater risk for illness. Cohen said that measuring many aspects of the immune system that could establish the link would require research subjects to submit to multiple blood tests and would be hard to measure because of the invasive nature of the tests.
However, identifying the conditions that can lead to colds might contribute to more prevention, researchers said. "And, telling people to reduce stress is never a bad thing," added Cohen.
Research contributors on this project include Professor of Pathology Dr. Bruce Rabin, Professor of Otolaryngology Dr. William Doyle, Associate Professor of Otolaryngology Dr. David Skoner and Professor of Psychiatry Dr. Ellen Frank, all from the University of Pittsburgh School of Medicine; and Dr. Jack Gwaltney, professor of medicine at the University of Virginia Medical School.