The Glasers found that people who had more stress had a poorer response to the vaccine. In other words, they were more likely to get sick. In short, stress seemed to hinder the immune system's resistance to infections and its ability to protect itself against them.
"We were surprised at how strong and consistent the data was across groups," Kiecolt-Glaser said. "We gave different vaccines to different populations but the effect was still the same."
Cohen's research found that work-related stressors and interpersonal conflicts at home were the two most powerful predictors of who gets a cold.
Specifically though, he determined that the kind of work-related stressors that matter most are economic ones, and it's these financial concerns that can also create ongoing stressors at home.
"If you have an enduring economic stressor, you're five times more likely to get a cold than people who don't have any ongoing enduring stressors," Cohen said. His data showed that people who were unemployed or underemployed at jobs that weren't commensurate with their training were at five times greater risk of catching a cold.
As for why economic stress made you more prone to getting sick, Cohen speculated, "Our guess is that the effect of unemployment is due to the fact that it is an extremely potent stressor influencing multiple factors in a person's life including issues like self-esteem, feelings of control as well as the obvious implications for paying rent and putting food on the table."
When asked whether other enduring economic stressors facing consumers, such as a potential recession or significant drop in the stock market would have a similar impact, he replied, "It's hard to say. These are a little more abstract than being unemployed. However, they do generate some of the same threats."
If there is any silver lining to that stress-related cold, it could be that it may be a red flag for bigger stress issues that beg to be addressed.
"Sometimes a cold lets you know that you've got to do something about stress," said Dr. James Gordon, psychiatrist and director of the Center for Mind-Body Medicine in Washington, D.C. "It's important to use the experience to look at what stress is and how it could be affecting you."
When people are stressed, their health behaviors often suffer. They might not exercise, they eat the wrong foods, they don't sleep as well, and they might drink or smoke more. None of this is good for the immune system, pointed out Kiecolt-Glaser.
And she said that on the psychological side, they tend to withdraw from others.
"Those personal relationships are one of the better things you can do from the standpoint of immune response," she said.
"If you can downturn from the stress response and shift gears into a relaxation mode, you will go a long way toward helping your body to counter the negative impact of stress on your health," Sternberg said. You can do this in several ways, including meditation, exercise, tai chi, yoga, a healthy diet, getting together with family and friends, and prayer, she said.