In the centuries since, millions of people have assumed the same. But in recent decades, this view has come to be dismissed by much of the medical establishment as too squishy to dignify. Emotions and beliefs can't have anything to do with health--it's all chemical reactions and deterministic molecule exchanges intermediated by proteins and neurons. Emotions--really! Today, most medical schools don't teach mind-body connections, and those who raise them in academic medical circles are looked down upon.
Into this breach steps Dr. Esther Sternberg, an M.D. and medical researcher. Her credentials could not be more establishment. Just consider the length of the polysyllabic title she carries: Director of the Molecular, Cellular, and Behavioral Integrative Neuroscience Program and Chief of the Section on Neuroendocrine Immunology and Behavior at the National Institutes of Health. Whew! The National Institutes of Health is the primary U.S. government medical-research agency and represents the very epitome of the hard-science point of view. Yet Sternberg has just published an impressive book, "The Balance Within: The Science of Connecting Health and Emotions," which argues that relationships between mental state and physical well-being are not only real, they are grounded in human physiology and evolution.
Sternberg explains that she started down the path of wondering about this subject when, as a young researcher, she was assigned a project on arthritis. She and her colleagues were to proceed by inducing the condition in a strain of arthritis-susceptible lab animals, called Lewis rats, that had been specially bred to be subject to this disease. Sternberg realized that medical researchers who worked with Lewis rats never seemed to ask themselves why these particular types of mice were more likely to get arthritis than rodents as a group.
So she designed a test that was, more or less, designed to determine the mental state of rats, at least as can be shown by measure stress hormone response, the medical manifestation of stress. (When people are under stress, their blood shows elevated levels of certain hormones, among them cortisol; rats under stress elevate their blood levels of a similar substance, costerone.) What she found was that arthritis-resistant rats were the ones with the highest stress-response levels--added hormones in their blood were blocking the inflammations that researchers were trying to reduce. Lewis rats that easily succumbed to arthritis, on the other hand, lacked the blood proteins.
Eventually, Sternberg became convinced that there are clear linkages between brain state and the health of the rest of the body, particularly as involves immune-system response. "The Balance Within" lays out in great detail the evidence for this conclusion, which can be summarized thus: The brain is not a monolithic lump but a group of mini-brains that exert different types of influence on the rest of the body. Chemically, different parts of the brain are ascendant depending on a person's emotional state and can send different messages. Positive chemical signals from the brain help the rest of the body organize and boost immune function, cellular health, and fertility; negative chemical signals may dampen or interfere with these health cues.
In sum, Sternberg thinks, parts of the body--especially the immune system--are not just chemical automatons working in isolation but rather subtly linked to emotional state, in animals but especially in people. A person with a well-balanced emotional state may be less likely to get sick, owing mainly to better immune-system regulation. I'll leave it to readers to discover for themselves Sternberg's amusing accounts of how her highly rational fellow researchers responded to this theory. Their stress levels clearly rose--bad for health, of course--as Sternberg propounded her idea that emotions are not just "moods" but integral to a feedback system that helps govern health. Some researchers especially found unsettling the part of Sternberg's thinking that implies that beliefs aid health: Someone who believes life has purpose, or (rightly or wrongly) believes in higher powers, may achieve better health through composure than someone who feels anxiety brought on from the assumption that life is amoral or pointless.