All in Your Head? Yes, and Scientists Are Figuring Out Why
By Sharon Begley
17 March 2006
(Copyright (c) 2006, Dow Jones & Company, Inc.)
IF ASTHMA IS a disease of the airways, why were volunteers with the disease undergoing functional MRI scans of their brains?
Psychological stress has long been known to make asthma worse. Undergraduates with the disease suffer worse symptoms during final exams, for example. But exactly how anxiety can leave the gray matter and get down to the airways has been a mystery. Scientists at the University of Wisconsin, Madison, decided to peek into asthmatics' brains to try to identify neural circuitry that turns thoughts and feelings into signals that affect the lungs.
When volunteers who inhaled an asthma trigger, such as cat dander, looked at asthma-related words such as "wheeze," their symptoms worsened -- and their brain seemed to show why. Activity rose in the insula and the anterior cingulate cortex, regions that connect to areas that process emotions. That increased activity worsened inflammation and obstruction of the airways.
"These changes in brain activity might be part of a pathway by which emotions affect asthma symptoms," says Richard Davidson, who led the 2005 study.
Mind-body science has turned up fascinating correlations between mind and health over the years. Also called psychosomatic medicine, it has found that social isolation tends to raise levels of stress hormones and blood pressure, and to produce a weaker antibody response to flu vaccine, while being socially engaged is associated with less coronary artery disease, fewer colds and other infections, and longer life. It has shown that depression raises the risk of death from coronary artery disease. None of this, the studies find, is explained by lonely, sad people doing self-destructive things like smoking or drinking too much. The mental state itself predicts the health problems.
FOR ALL ITS intriguing discoveries, however, mind-body science has been plagued by being, well, brainless. That is, researchers couldn't explain how intangibles such as thoughts and emotions get translated into something "real" enough to exert physiological effects. That is finally changing.
"With the explosion in neuroscience, mind-body medicine can now bring the brain in," says Richard Lane of the University of Arizona, Tucson, president of the American Psychosomatic Society. "That holds out the possibility of moving from correlation to mechanism," of showing how mind is related to body.
At the society's annual meeting this month, scientists presented a slew of findings of how mind affects body through the brain. For instance, depression and hostility seem to increase levels of proteins associated with inflammation and risk for coronary artery disease, reported Thomas Kamarck, of the University of Pittsburgh, and colleagues.
"There may be an association between psychological factors and these inflammatory markers," he says. Both are associated with increased activity in the part of the nervous system that is activated by the hypothalamus and brain stem. These structures are perfectly placed to turn feelings into physiology. They receive signals from the brain's emotion center and send signals down into the body, where they affect heart rate and respiration. In this way, heightened fear and other negative emotions might affect heart rate.
Depression, too, leaves its mark on the brain. Scott Matthews of the University of California, San Diego, used fMRI, which detects brain activity, to measure what happens when people assess facial expressions, while simultaneously monitoring their vital signs. In those with major depression, greater activity in the amygdala, which processes fear and assesses signs of threat, was related to arousal in the part of the nervous system that affects heart rate and blood pressure.
IN A SORT of toe-bone-connected-to-the-foot-bone chain, high levels of activity in the amygdala, which connects to the hypothalamus and brain stem, "is associated with cardiac changes that may increase the risk of dangerous arrhythmias," says Prof. Matthews.
Mental stress can wreak bodily havoc in several ways. For one, when the amygdala registers threats and their associated stress, it activates the hypothalamus, which signals the adrenal glands to flood the body with stress hormones. Those suppress the immune system. Also, "people who show greater activation in the amygdala and cingulate cortex during a demanding cognitive task show a greater rise in blood pressure," says Pittsburgh's Peter Gianaros. The two structures' output to the hypothalamus and brain stem allow the stress they register to raise blood pressure, which is linked to a higher risk of heart disease.
Bringing the brain into mind-body science may remove the stigma from the phrase, "it's all in your head." "Doctors are aware that how you think and feel can affect your biology, but because the mechanisms haven't been identified it hasn't been taken seriously," says Robert Rose, who directs the Mind Brain Body and Health Initiative at the University of Texas Medical Branch, Galveston. But as "brain-based explanations give the findings greater depth and credibility," Prof. Lane adds, "doctors might be more likely to recognize the importance of the mind."
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