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Robert Sapolsky, a neuroendocrinologist and John A. and Cynthia Fry Gunn Professor at Stanford University, has focused his research on issues of stress and neuronal degeneration, as well as on the possibilities of gene therapy strategies for protecting susceptible neurons from disease.
In his Science article, entitled ‘Why Stress Is Bad for Your Brain’ Dr. Sapolsky summarizes what has been found so far as scientists tune up high-resolution MRI to take pictures of the hippocampus. The hippocampus is the region of the brain responsible for explicit, declarative memory for knowing a fact like an address or the name of a friend, and knowing that one knows it. Its neurons are rich in glucocorticoid receptors; this is the region where animal studies have shown that stress hormones can damage neurons.
According Sapolsky, in rats, short-term exposure to glucocorticoids causes neurons to shrink, but they rebound when levels of the hormones return to normal. Long-term exposure causes irreversible damage. The same effect seemed to occur in the study of people with Cushing’s syndrome. Their brain atrophy was reversed when the tumor was removed, stopping the overflow of glucocorticoids.
Sapolsky also spends time annually in Kenya studying a population of wild baboons in order to identify the influence of social hierarchy on primate health – how social rank affects physiology and health; whether it is high- or low-ranking animals that are most stressed in a dominance hierarchy; and how the stressful characteristics of social rank have adverse adrenocortical, cardiovascular, reproductive, immunological, and neurobiological consequences.
Sapolsky has shown that the same glucocorticoids that flood the bloodstream during a stressful event remain at high levels for months or years if the baboon has a stressful life. For example, if a male baboon is always in fear of an attack by the dominant male in his troop. The baboons that handle stress best, in contrast, are those who have formed stable social connections. Dr. Sapolsky has found that a key to handling stress may be cultivating friendships. Males who spend the most time grooming and being groomed by females and playing with infants have the lowest levels of stress hormones.
Dr. Sapolsky believes that stress exerts its strongest effects on gastrointestinal function, sleep, sex drive and blood pressure. For example, blood pressure will rise only two seconds after a stressful event – an especially dangerous reaction for Type A’s personality, who see stressors everywhere. In fact, Sapolsky argues that Type A behavior is a greater risk factor for cardiovascular disease than smoking.
Sapolsky is the author of a popular book, ‘Why Zebras Don’t Get Ulcers’, where he discusses the physiology of the stress response, and why zebras don’t get ulcers, or heart disease, diabetes and other chronic diseases. Sapolsky suggests that people develop such diseases partly because our bodies aren’t designed for the constant stresses of a modern-day life, rather, they seem more built for the kind of short-term stress faced e.g. a zebra outrunning a lion. Sapolsky also explores stress’s role in heart disease, diabetes, growth retardation, memory loss, and autoimmune diseases such as multiple sclerosis.