Numerous studies show that stressors can have profound emotional and physical health consequences. Stressful events trigger cognitive and affective responses, which in turn induce sympathetic nervous system and endocrine changes that ultimately impair immune function. (LINK TO SOURCE Chrousos & Gold, 1992, pp.1244-1252)

The immune function is impaired by stress through emotional and/or behavioral manifestations, including anxiety, fear, tension, anger and sadness, as well as in physiological changes, such as heart rate, blood pressure, and sweating. Researchers have suggested that these changes are beneficial if they are of limited duration (LINK TO SOURCE Chrousos and Gold, 1992), but when stress is chronic the system can’t maintain equilibrium or homeostasis.

Two meta-analyses of the literature show a consistent reduction of immune function in healthy people under stress. The first, by Herbert and Cohen in LINK TO SOURCE 1993, examined 38 studies of stressful events and immune function in healthy adults. They included studies of acute laboratory stressors (e.g. a speech task), short-term naturalistic stressors (e.g. medical examinations), and long-term naturalistic stressors (e.g. divorce, bereavement, care-giving, and unemployment.)

They found consistent stress-related increases in the numbers of white blood cells, as well as decreases in the numbers of helper T cells, suppressor T cells, and cytotoxic T cells, B cells, and natural killer cells. This means that there is evident weakening of the immune system, increased susceptibility to chronic inflammatory states and propensity to chronic disease.

The second meta-analysis, by Zorrilla et al. in LINK TO SOURCE 2001, replicated Herbert and Cohen’s work. Using the same study selection procedures, they analyzed 75 studies of stressors and human immunity and came to the same conclusion. In my next post, we’ll get into this more deeply, including a consideration of coping skills.