The poets were right after all. When you're depressed you feel heaviness in the heart. The brain and the heart are connected—by much more than just metaphor.
Depression, scientists now know, has many effects on the body. It disturbs the immune system, igniting inflammatory responses to cellular events. It alters bone metabolism, leading to osteoporosis. It is marked by dysregulation of the stress response system, so the body is, in effect, worn out by overexposure to the alarm system of stress hormones. Depression stiffens the body's response to insulin, the hormone that helps regulate energy metabolism. Experts have begun to shift their view of depression, now seeing it as a medical condition that has psychiatric manifestations.
But of all the systems depression trucks with, none is more distinctly vital than the heart. Even momentary alterations in cardiac activity can make the difference between life and death. Depression seems to tug many heartstrings. "There is an embarrassment of riches," says Robert Carney, Ph.D., professor of medical psychology at Washington University in St. Louis. "There are many possible links between depression and heart disease."
The body has its ways of translating thoughts and feelings into physiology. "Negative feelings influence in an acute way the hormones traveling through the body," observes Gregory E. Miller, Ph.D., assistant professor of psychology at the University of British Columbia.
"When you're depressed, the vascular system and the heart are affected," says K. Rama Ranga Krishnan, M.D., chief of psychiatry at Duke University. His own studies show that stress leads to ischemic changes in the heart, starving it of oxygen.
Over the past decade, researchers have found that by itself depression is a powerful risk factor for heart disease—equal to smoking, hypertension or diabetes. It raises the risk of dying from heart disease by 400 percent in the six months after a heart attack. Multiply that by the number of cardiac patients who experience more than transitory depression—a third of heart patients.
Depression also commonly follows cardiac bypass surgery and stroke. A large study of middle-aged men in Wales has shown that those who have depression or anxiety are more than three times as likely to have a fatal stroke as peers who are not depressed.
Men are not unique. Last month, Duke researchers reported that women with coronary artery disease are twice as likely to die if they exhibit symptoms of depression.
That depression aggravates cardiovascular disease and makes it especially lethal now seems well established. "Depression is common in cardiac disease," says Nancy Frasure-Smith, Ph.D., senior research associate at the Montreal Heart Institute. "It's a normal response to heart disease. But it appears to be toxic. Depression is a predictor of prognosis in the wake of myocardial infarction, bypass surgery, heart failure and angina."
Her own studies suggest that the toxic element is negative affect, the tendency to experience negative moods and emotions, specifically hostility—"not perceiving that people love you." It lurks in the background as a personality trait of the depressed. Superimposed on it is the cyclical nature of depressive episodes, mostly set off by stress.
If depression aggravates heart disease, to what degree might the same processes be setting the stage for heart disease in those whose only known affliction is depression? "We don't know whether depression promotes atherosclerosis," says Carney. "But it does do something to patients who have it."
"It's probably a two-way relationship," says Krishnan. "Having cardiac disease leads to high rates of depression. And in itself that depression will influence the cardiac disease and whether you recover." It is, for now, a "massive puzzle," he says. The pieces are reasonably clear, if how they fit together is not.
Heart-rate variability. Normally, the healthy heart varies its rate somewhat from beat to beat, even at rest. This characteristic, known as heart rate variability (HRV), gives us leeway to respond to the demands of our ever-changing environment. Diminished HRV is a known independent risk factor for cardiac mortality. It increases the likelihood of sudden death, and almost all instances of sudden death are due to ventricular arrhythmia. It sounds contradictory, that heart rate variability underlies cardiac stability, but the body needs its margins; it's the foundation of human adaptability.
One of the first researchers on this beat was Washington University's Carney. First in a study of 39 patients, and then in a larger look at 380 depressed and 420 non-depressed people, all recovering from a heart attack, patients were equipped with portable heart monitors for 24 hours. Carney found that HRV is diminished in those with depression. It makes no difference whether they have major depression or minor depression; any symptoms of depression seem to do it.
"Patients with even a few depressive symptoms were at the same risk of dying as patients with major depression," Carney reported. Low HRV, he calculated, accounts for more than half of the increased risk of death in cardiac patients with depression.
This particular physiologic impairment of the heart in depression packs a metaphorical punch; it's a direct parallel to, even an embodiment of, the behavioral impairment. Depression first and foremost limits the capacity of people to respond to the normal stimuli of their environment. Sufferers withdraw physically, psychically, and socially. The world contracts to a dark cave.
Tags:
body,
bone metabolism,
cardiac activity,
cellular events,
decade researchers,
depression,
duke university,
dysregulation,
embarrassment of riches,
energy metabolism,
heart,
heart disease,
heartstrings,
inflammatory responses,
medical psychology,
ranga,
robert carney,
sad,
stress hormones,
stress response,
thoughts and feelings,
university of british columbia,
vascular system,
washington university in st louis
