Researchers have confirmed scientifically what many people have long believed instinctively: You are more likely to catch a cold when you feel "stressed out."
In the clearest demonstration yet of the relationship between emotions and infections, researchers in Pittsburgh and Britain found that high levels of psychological stress could nearly double a person's chances of catching a cold by lowering resistance to viral infection.
Results of the carefully controlled study, conducted with more than 400 volunteers at the Medical Research Council's Common Cold Unit in Salisbury, England, are published in today's issue of the New England Journal of Medicine.
In an accompanying editorial, Dr. Morton N. Swartz of Massachusetts General Hospital praised the study for avoiding the many deficiencies that have marred previous investigations of the relationship between stress and disease.
Although few health professionals doubt that emotional distress plays a role in many ailments, from heart attacks and cancer to allergies and ulcers, precise studies of the relationship and a full understanding of the mechanisms involved are still wanting.
In the latest study, directed by Dr. Sheldon Cohen, a psychologist at Carnegie-Mellon University in Pittsburgh, three measures of stress were used to derive a total stress index that would reflect how people felt.
The three measures were: events in the preceding year that the subject perceived as having a negative effect on his or her psychological state, the degree to which the subject perceived current demands as exceeding his or her ability to cope, and an index of current negative emotions.
In an interview yesterday, Dr. Cohen said the technique avoided the assumption that particular events necessarily caused distress, since people do not always react adversely to the same events.
The volunteers -- 154 men and 266 women, all of whom were healthy at the start -- were housed in isolated areas of the cold unit for two days before and a week after they were exposed to a nasal wash containing one of five cold viruses or an innocuous salt solution.
Measurements were taken of various immunologic factors, such as the level of white blood cells and the presence of antibodies that would fight cold viruses.
Assessments also were made of the participants' diet and exercise habits, smoking and drinking patterns and other health and lifestyle practices that could conceivably influence their susceptibility to colds.
The researchers also assessed two personality factors, self-esteem and a sense of personal control, that could play a role in susceptibility to illness.
All these factors were taken into account when the results were analyzed.
After the volunteers were exposed to the cold viruses, the researchers examined their upper respiratory secretions for evidence of viral infection.
Among those at the low end of the stress index, 74 percent showed infection by the virus involved; at the high end, 90 percent were infected.
The researchers then looked at which volunteers actually developed clinical symptoms of a cold. In the low-stress group, 27 percent did; in the high-stress group, 47 percent. No relationship was found between immunity measures and the occurrence of viral infection or clinical colds.
"This does not mean the immune system was not involved, just that the factors we studied were not responsible for the observed relationship between stress and illness," Dr. Cohen said.
He and his co-authors, Dr. David A. J. Tyrrell of the cold unit in Salisbury and Dr. Andrew P. Smith of the University of Wales in Cardiff, said they believed that stress may modify some of the body's front lines of defense against viral infection, such as the amount and consistency of nasal mucus and the production of interferon, a natural anti-viral agent, in the nasal passages.
Dr. Cohen said that the findings did not lead to specific recommendations to help avoid colds.
"This study is just a first step in trying to understand the relationship between the central nervous system and the
immune system and what it means to disease," he said.