The Links Between Stress and Illness

If chronic stress can weaken the immune system, are people who are stressed in life more likely to become sick? Might some people, for example, be psychologically more susceptible than others to catching the flu? Sheldon Cohen and his colleagues (1993) conducted a fascinating and elaborate study to help answer this question. They paid 420 volunteers to spend nine days in a medical experiment and risk exposure to a common cold virus. In the first two days, participants filled out several questionnaires, including one that measured recent stressful experiences in their lives. They also received a physical examination, including a blood test. Then, to simulate the person-to-person transmission of a virus, the researchers dropped a clear liquid solution into each participant’s nose. Those randomly assigned to the control group received a placebo saline solution. Others, less fortunate, received a cold virus in doses that tend to produce illness rates of 20% to 60%.

For the next week, participants were quarantined in large apartments, where they were examined daily by a nurse who took their temperature, extracted mucus samples, and looked for signs of colds, such as sneezing, watery eyes, stuffy nose, and sore throat. (The participants did not realize it, but the nurse also kept track of the number of tissues they used.) All participants were healthy at the start of the project, and not a single one in the saline control group developed a cold. Yet among those exposed to a virus, 82% became infected, and 46% of those who were infected caught a cold, symptoms and all. A virus is a virus, so often there is no escape. Most interesting, however, is that life stress made a difference. Among those who became infected, high-stress participants were more likely to catch a cold than were the low-stress participants—53% compared with 40%. In short, people whose lives are filled with stress are particularly vulnerable to contagious illness.

In a follow-up of this experiment, Cohen and others (1998) interviewed 276 volunteers about recent life stressors, infected them with a cold virus, and then measured whether they developed a cold. They found that some types of stress were more toxic than others. Specifically, people who had endured chronic stressors that lasted for more than a month (like ongoing marital problems or unemployment) were more likely to catch a cold than those who had experienced acute short-term stress (such as a fight with a spouse or a reprimand at work).