According to research published in Psychosomatic Medicine (March 1999;61:175–180), stress may worsen the symptoms of a cold or the flu. The study involved 55 subjects who were intentionally exposed to Influenza A virus. Before exposure, participants completed questionnaires assessing their stress levels. They were then quarantined and monitored. Researchers measured mucus production, symptom severity, and levels of interleukin-6—a protein involved in immune response. Subjects reporting the highest stress levels experienced more severe symptoms, greater mucus production, and higher interleukin-6 levels.
Similar findings were reported in Epidemiology (May 2001;11:345–349). In a survey of more than 1,100 staff and students at a Spanish university, individuals who perceived themselves as stressed were more likely to develop a cold. The highest incidence of colds was seen in pessimistic individuals—those with a consistently negative outlook on life.
