Psychological Stress and Susceptibility to the Common Cold

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Psychological Stress and Susceptibility to the Common Cold

Every year millions of people are exposed to the virus which causes the common cold. Yet of these, most will escape infection and/or illness. Among the factors routinely used to explain why some become ill while others do not is the individual's level of stress, which is thought to suppress host resistance. Yet previous research studies on this question have been subject to a variety of technical criticisms. To quote researcher Sheldon Cohen, "It is not known whether psychological stress suppresses host resistance to infection." Now in a recent study conducted at the Medical Research Council's Common Cold Unit in England, Cohen and his colleagues conclude that volunteers with the highest levels of stress run twice the risk of getting a cold compared to those with the lowest levels, and more than five times the risk of becoming infected with the virus.

Biomedically speaking, "stress" refers to any adverse physical, mental or emotional stimulus that upsets the organism's homeostasis. In the present study, 394 healthy human volunteers were assessed for the level of psychological stress present in their lives over the preceding year, then infected with the common cold virus. It was found that the susceptibility to both infection and subsequent disease correlated in a doseresponse manner with the level of psychological stress in the individual's life.

To determine the level of psychological stress, volunteers completed three forms of questionnaire designed to show the following:

- The number of major stressful life events judged by the subject as having had a negative impact on his or her psychological state during the preceding year;

- The extent to which current demands exceeded the subject's ability to cope (as perceived by the subject);

- An index of current negative affect. This was measured by asking the subject to indicate on a scale of 0-4 the intensity of a range of negative feelings -- hostility, sadness, nervousness, anger, depression, etc. -- experienced during the preceding week.

The test subjects were then given nasal drops containing one of five different respiratory viruses. A control group of 26 was given only saline nasal drops. The subjects were quarantined and monitored for the development of evidence of infection, which was measured by isolation of the virus from nasal washings, or by an increase in virusspecific antibody levels. Cold symptoms were assessed both by self-report and by clinicians, who examined participants daily for sneezing, watery eyes, sinus pain and other symptoms.

The results showed that the greater the individual's stress level, the higher the likelihood of being infected by the cold virus, and of developing cold symptoms. Of the 394 virus-exposed volunteers, 325 became infected and 148 developed colds. Ruling out a number of factors which might otherwise confuse interpretation of the results -- for example, age, sex, education, allergic status, weight, the season, the number of subjects housed together, and so on -- did not change the results.

Because the response was the same to a variety of different viruses, the authors suggest that stress suppresses a general resistance process in the host. Alternatively, stress may be associated with the suppression of many different immune processes. However, the relationships seen in this study were quite small, and depended for their significance on the magnification which results from using a very large group of subjects, and an accompanying editorial cautions that despite this study's improvements over preceding ones, there still may be other factors at play.

Source: New England Journal of Medicine, Volume 325(9), 1991

Institute of Noetic Sciences.

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By Nola Lewis

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