As the economy plummets to dramatic lows, the stress levels of Americans -- and possibly their susceptibility to cold and flu -- are soaring to stratospheric highs.
"My best guess is that those most impacted by the economic downturn will be at greater risk [of cold and flu]," said Sheldon Cohen, a professor of psychology at Carnegie Mellon University in Pittsburgh, and one of the country's leading experts on the relationship between stress and vulnerability to viral infections.
In one of Cohen's studies, he looked at the types of stress factors that make healthy adults more prone to catching a cold. He said he found that chronic, enduring stressors made the biggest difference.
Short-term stressors like a traffic jam, a fender-bender, or a quick turnaround project at work happen all the time and cause small changes in immune response.
But stressors that are ongoing and lasting a month or longer -- the bad marriage, the bad working situation -- are the kind most likely to make you come down with something.
"There's a fair amount of evidence from epidemiology and viral challenge tests that people exposed to chronic stress are at greater risk of catching a cold," Cohen said.
The connection between stress and the sniffles is a principle with which Colleen Hughes, a 26-year-old copy editor and part-time graduate student from Sunderland, Mass., is familiar.
"I tend to be a high-stress person, and I worry a lot," she said. "But I also seem to be more productive with stress and can work a lot faster."
Hughes said her stress makes her productive on the one hand, but it also makes her "mind go a mile a minute and makes sleep harder." And it's often during these times with "one issue after another and too much to get done" that she gets "a bit of a sore throat," which is typically how her colds start to blossom.
Immune researchers agree that prolonged stress can indeed weaken the immune system.
Key to this concept is the idea that the nerve chemicals and stress hormones (such as cortisol) affect the body's ability to fight disease and maintain health, Sternberg explained. When you have too much cortisol around because of chronic stress, it interferes with the body's ability to shut off production of pro-inflammatory cytokines, which are proteins produced by the immune system in response to infection.
Having too much of these cytokines means a viral infection and its symptoms linger -- making it harder for you to get rid of your cold.
"Stress can make you sick or help make you sick," said Janice Kiecolt-Glaser, a professor of health psychology at Ohio State University, who along with her immunologist husband Ronald Glaser, has spent several decades researching the influence of psychological stress on immune function.
In their work, they've looked at several different groups of people who experience a great deal of stress, including medical students and older adults who were caregivers. They measured how their immune systems responded when given a vaccine during high-stress times compared to their calmer counterparts.