Connections
Stress and Health in Everyday Life
In the "Executive Monkey" experiment, the stress from the shocks clearly produced long-term health problems for those monkeys. But what about humans? Most of us don't experience painful shocks on a regular basis, but do the stresses of everyday life take a toll on our bodies and on our health? The answer seems to be yes. The past forty years of research in this area have uncovered a strong link between stress and health, and the evidence grows stronger every year.
First, everyday stressors do activate our stress response system, increasing the production of the stress hormones. For example, a classic study by Frankenhaeuser (1978) measured the impact of an academic stressor (a major oral examination) on hormone levels over a 2-week period. The results show a dramatic increase in epinephrine and norepinephrine on the day of the exam.
More recent studies have demonstrated that even relatively brief, relatively minor stressors, such as being called on in class or being surprised by a pop quiz, elevate the levels of epinephrine and norepinephrine, as well as glucocorticoids. The high levels of these stress hormones can cause temporary uncomfortable symptoms such as muscle tension, headaches, and upset stomachs.
Levels of epinephrine and norepinephrine show increases at various times during the period -- owing to daily stressors. However, for students, an exam -- a major source of stress -- shows the largest increase in these hormones.
Stress Harm's Your Body's Organ Systems
Second, chronically high levels of stress hormones can produce long-lasting or permanent damage to your body. Although the physiological changes triggered by the hormones are helpful when we find ourselves in sudden danger, they are harmful to our health and may even speed up the rate of physical aging if they occur repeatedly or continuously at school or at work.
Stress can damage your heart. Chronic stress raises blood pressure, which over time causes damage to the heart and blood vessels and increases the risk of stroke. Also, high levels of glucocorticoids cause fat cells to release fatty acids into the bloodstream for fuel. If we don't need to burn the fat for energy, it builds up on the walls of our blood vessels (especially those damaged by high blood pressure), reducing blood flow to the brain and muscles and increasing the risk of heart attack.
Stress can damage the digestive tract. It causes a reduction in enzyme production and a reduction in blood flow to the stomach and intestines, making the lining of the stomach more vulnerable to damage from hydrochloric acid and ulcer-causing bacteria.
Stress can damage your brain. Recent studies by Sapolsky (1996) and others have demonstrated that, in rats and monkeys, elevated levels of glucocorticoids cause permanent damage to neurons in a part of the brain called the hippocampus, a structure involved in learning and memory. Although these types of experiments have not been performed on humans, new evidence from brain scans suggests that the hippocampus is smaller than normal in chronically depressed patients (who tend to have elevated glucocorticoid levels in their bloodstreams) and military veterans with several years of combat exposure. The constant high levels of stress hormones in these individuals actually may have caused the hippocampus to shrink.
