Jerry Seinfeld got a big laugh when he joked about a survey that found that the fear of public speaking ranks higher in most people's minds than the fear of death. "In other words," he deadpanned, "at a funeral, the average person would rather be in the casket than giving the eulogy."
It's a funny line, but the comedian may have had it backward. Short-term stresses like speaking in public, it turns out, boost your immune system in ways that tend to keep you out of the coffin, not put you in it. That's one of the findings that emerged from a study of 30 years of stress research published last week in Psychological Bulletin, a journal of the American Psychological Association. In a meta-analysis of more than 300 studies involving some 19,000 subjects, psychologists Gregory Miller at the University of British Columbia and Suzanne Segerstrom at the University of Kentucky combed through thousands of pages of research in search of common threads.
What they discovered is that modern stresses prompt complex reactions beyond the simple fight-or-flight response--the primordial motivator that sends your heart racing and pumps up your blood pressure. In particular, stress triggers a variety of changes in the immune system--some beneficial, some decidedly less so--depending on how long the stress lasts and whether there is an end in sight. To help make sense of it all, Miller and Segerstrom divided the modern universe of stressful situations into several major categories.
GIVING A SPEECH
When test subjects were asked to speak in public or do mental math in the lab, the tasks tended to mobilize their fast-acting immune response--the body's all-purpose defense system for fending off infection and healing wounds. Compared with controls, people subjected to such short-term stresses had up to twice as many natural killer cells in their blood ready to fight the early stages of infection.
TAKING A FINAL EXAM
Short-term stressors with high stakes--like the SATs or the bar exam--appeared to hinder the immune response by suppressing Th1 cells, which normally activate killer cells and wound-healing chemicals called cytokines. This suppression can also boost the concentration of Th2 cells, which produce antibodies and can make allergies worse.
SURVIVING NATURAL DISASTERS
The results were less consistent for stressful events that give rise to a succession of future hardships, such as the death of a spouse or the effects of a natural disaster like an earthquake. Researchers believe that bereavement causes a decline in natural immunity, while a handful of studies suggest the trauma following a disaster may trigger a small immune boost.
Chronic stressors that alter a person's role in society or sense of himself and show no sign of ending, such as unemployment, permanent disability or the need to care for a parent with dementia, are bad news. They have significantly negative effects on almost all immune functions.