Does Stress Lower Resistance?

This time you really outdid yourself. You’re one of 420 volunteers in a medical experiment for which you agreed to risk exposure to a common-cold virus. You’ll be reimbursed for all travel expenses, and for nine days you’ll receive free room and board in the clinic. So, you pack your bags, check in, and sign an informed-consent statement.

The first two days are hectic. First, you’re given a complete medical examination that includes a blood test. Then you fill out a stack of questionnaires. You answer questions about your mood, personality, health practices, and recent stressful experiences (such as a death in the family, pressures at work, or the breakup of a relationship). Then it happens. To simulate the person-to-person transmission of a virus, an attendant drops a clear liquid solution into your nose. If you’re lucky, you were randomly assigned to the control group and receive only saline. If not, then you’re in an experimental group and receive a low dose of a cold virus—just what you need. These exposures tend to produce illness at rates of 20 to 60 percent.

You are now quarantined in a large apartment for seven days—alone or with one or two roommates. Every day, you’re examined by a nurse who takes your temperature, extracts a mucus sample, and looks for signs of a cold: sneezing, watery eyes, stuffy nose, hoarseness, sore throat, and cough (you don’t know it, but the nurse also keeps track of the number of tissues you use). Basically, the researchers are interested in two results: (a) Are you infected (is there a virus in your system)? (b) Do you have a cold (as judged by the various symptoms)? The researchers are trying to determine if there is a link between the recent stress in your life and your susceptibility to illness. 

Make a Prediction 

On the basis of the questionnaires initially filled out, you and others are classified as having a high or low level of stress in your life. Does this psychological factor make a person more or less vulnerable to viral infection? Among those who are infected, does recent life stress elevate the risk of catching a cold? All participants were healthy at the start of the project—and not a single saline control subject developed cold symptoms. Among those exposed to the virus, however, 82 percent became infected, and 46 percent developed cold symptoms. A virus is a virus, and there is no escape. But were the rates significantly different among the high- and low-stress groups? What do you think? 

1. Were high stress participants more likely to become infected?

2. Were high stress participants more likely to catch a cold?

The Results 

In 1985, the prestigious New England Journal of Medicine published a study that failed to find a link between psychological factors and medical outcomes. In an accompanying note, the journal’s editor took the opportunity to scoff at the very notion that a person’s mental state can affect physical health. Six years later, Sheldon Cohen and others (1991) published the study just described in the same New England Journal of Medicine—an event that marked a “turning point in medical acceptance of a mind/body connection” (Kiecolt-Glaser & Glaser, 1993). The results of this study were convincing. Life stress was not correlated with the rate of infection. Among those exposed to a virus, 85 percent of the high-stress participants and 81 percent of the low-stress participants became infected. Among those who were infected, however, high-stress participants were more likely to catch a cold than were the low-stress participants—53 percent compared to 40 percent. In fact, when participants who had been housed with infected roommates were eliminated from the analysis (because of the risk that they had been reexposed), the high stress participants were still more likely to catch a cold than their low-stress counterparts—45 percent to 28 percent. Thus, once infected, people whose lives are filled with stress are particularly vulnerable to illness. 

What Does It All Mean?

This study reveals that there is a correlation between life stress and susceptibility to illness. Correlations do not prove causality, however, so we cannot conclude from this study alone that stress per se has this effect (it’s theoretically possible, for example, that people are under stress because they are physically vulnerable). However, other researchers are finding that stress lowers resistance and compromises the immune system, the body’s first line of defense against illness. Studies show that the activity of the immune system’s white blood cells, which are part of that immune defense system, can be altered temporarily in participants who are exposed to even a mildly stressful laboratory experience—such as a difficult mental task, a gruesome film, the recollection of bad memories, loud noise, or a bad social interaction (Straub & Cutolo, 2018). This research has profound implications. Until the last few decades of the 1900s, psychological and medical researchers believed that the human brain and immune system were separate and noninteracting. Not so! We now know that the organs of the immune system are richly endowed with nerve fibers, providing a direct pipeline to the brain—and that psychological factors such as stress can play an important role on our health. The result is a new field that focuses on the seamless interplay of mental and physical health. This new field is called psychoneuroimmunology: psycho for mind, neuro for the nervous system, and immunology for the immune system (Ader, Felton, & Cohen, 2001). Psychoneuroimmunology is generating a great deal of excitement in all areas of psychology.

Next - Activity 6: Thinking About Research: The Effects of Reward and Punishment on Decision Making

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