The Mind and the Heart: They Really Are Connected

Studies demonstrate that there s a potent relationship between mental stress and heart disease

YOUR HEART pounds with anxiety. Skips a beat from fear. Sinks when you hear disappointing news. "Everyone knows, intuitively, that there's a relationship between mental stress and heart health," says Alan Rozanski, MD, a cardiologist at St. Luke's/Roosevelt Hospital Center in New York City. "It's even in the Bible. When Jacob heard the news that his son, Joseph, was alive after having been missing for 22 years in Egypt, his 'heart fell' from the shock of it. Biblical experts suggest that means he had a heart attack."

But some doctors "are skeptical of mental stress's role in heart disease," Dr. Rozanski comments. Part of the reason may be that stress is tricky to define. "It's individualistic and subjective," notes Robert Carney, PhD, a psychologist at the Washington University School of Medicine in St. Louis. Each person feels and interprets mental stress in a different way. To one person, stress might mean the bleak feeling of depression; to another, it's simply being pressed for time.

But lately, stress has been getting more scientific attention. There has been a growing amount of research, including animal studies, population surveys, and tests of people's responses to stress in laboratory settings. Much of the evidence has to do with the impact of mental stress in heart disease that has already been diagnosed--for example, showing that depression increases the risk for a second heart attack. But there's growing evidence that the mind plays a role in the development of heart disease, too. "Stress is a continuum throughout the heart disease process," says Dr. Rozanski.

Following, several psychological factors that have been investigated for their impact on the heart.

The role of personality traits
In the 1970s, researchers thought they had drawn a conclusive link between mental health and heart disease with the idea of the type A personality: the driven, competitive workaholic at war with the world--and on the verge of a heart attack. But the link didn't hold up in research. There are plenty of ambitious workaholics whose hearts are perfectly fine, so scientists were left wondering whether character traits really made a difference.

When researchers began to tease out the different components of Type A behavior, however, they got some intriguing results. Ambition and drive, they found, aren't necessarily bad things, heart-wise. But hostility is a different story.

This spring, a study from the University of North Carolina showed that anger-prone people have a nearly threefold higher risk than others of suffering a heart attack or dying from heart disease. The researchers gave an anger-scale test to 13,000 men and women, asking them questions about whether they tended to fly off the handle, say unkind things when angry, or become irate when slowed down by others. The higher they scored on the anger test, the greater their risk for heart trouble over the course of the study, which lasted several years.

Another recent study, this time from the University of Michigan, showed that hostile people experienced larger and longer-lasting rises in blood pressure than others when they were asked to relive an angry memory. And a third study, from California, indicated that the effects of hostility appear to take hold relatively early in life. Young adults with above-average scores on an anger test were more likely to exhibit evidence of calcification in their coronary arteries--a beginning step in hardening of the arteries.

In addition to its potential to raise blood pressure and contribute to hardened arteries, researchers believe that anger arouses the involuntary nervous system--the network that controls unconscious bodily functions like digestion, sweating, and heartbeat. Specifically, they think it prompts the release of stress hormones such as cortisol and catecholamines (cat-e-COL-uh-meenz). Over time, having too many stress hormones floating through the system can damage the heart muscle and the delicate linings of surrounding blood vessels as well as disrupt the heart's electrical rhythm. In addition, stress hormones trigger the biochemical process that causes blood platelets to become sticky and clump together--a process that has been implicated in the formation of artery-clogging plaque.

Of course, people who have hostile attitudes tend to engender angry conflict more often, which only compounds the biochemical cascade and thereby increases their risk for developing or worsening heart trouble.

How acute stress exerts an effect
Since hostility tends to persist over time, it's regarded as a form of "chronic" stress. But anybody can get angry sometimes, whether or not he or she has a hostile personality, just as anybody can sometimes have an emotional eruption of frustration, tension, or even sadness. These are forms of "acute" stress. And acute stress can work in a more immediate fashion in patients with coronary artery disease to trigger a form of heart trouble called ischemia, in which the blood supply to the heart is briefly interrupted.

Acute stress increases the heart rate; causes blood vessels to constrict (thus raising blood pressure); and increases the body's demand for oxygen. That, in turn, is what can induce ischemia--or, if there's a clot of plaque present, cause the clot to detach itself from an artery wall and block a blood vessel, bringing on a heart attack.

The effect of acute stress on ischemia can be studied in the lab. According to Washington University's Dr. Carney, about half of all people who are prone to ischemia show evidence of it during stressful tasks, like taking a math test or engaging in an emotionally difficult conversation.

Depression hurts the heart, too
Many studies have shown that people who become depressed after a heart attack or other cardiac "event" are more likely than others to die from heart problems. Evidence from Montreal's McGill University has linked depression with a three- to four-fold greater likelihood of dying within the first year and a half after a heart attack.

Depressed people also appear to be at higher-than-normal risk for developing heart disease in the first place. In a recent study from Ohio, for example, depressed men and women were both more likely than their non-depressed counterparts to develop heart problems. All had taken a depression test in 1982 when they were heart disease-free. Ten years later, those whose test scores showed evidence of depression were over 70 percent more likely than the others to have had a heart attack or to have developed ischemia or other evidence of heart disease.

Scientists offer several possible explanations for the depression-heart disease link. It could simply be that depressed people are less likely to follow lifestyle recommendations to prevent or treat heart problems. "Depression affects how people take care of themselves," says Dr. Carney. They may not adhere to a heart-healthy diet or take cholesterol-lowering medication, for example. Depressed people are also more likely to smoke--a major heart-disease risk in itself--and less likely to quit. Indeed, research just released from the Johns Hopkins University School of Medicine showed that heart-attack survivors diagnosed with depression were less likely than other patients to adhere to treatment recommendations designed to reduce their risk for future cardiac events.

It may also be that depressed people have a poorly regulated involuntary nervous system. "Depressed people with heart disease have a lower heart rate variability," says Dr. Carney. "Your heart normally increases or decreases its beat as you do things like climbing the stairs or sitting still. But it doesn't show the same flexibility in depressed patients," who are thereby more subject to unusual glitches in the heart's adaptability.

What's more, depressed people, like those who are anxious or hostile, "are under a high degree of arousal most of the time," says Dr. Carney, meaning that they tend to secrete relatively high levels of stress hormones. "That's not a good thing," he points out. Chronically elevated levels of stress hormones can hasten the progress of atherosclerosis and thereby increase the risk for heart disease over time.

The toll on a lonely heart
The McGill researchers who studied depression and heart attack death noted in a later study that depressed people who live alone or have little contact with friends and relatives are at greater risk of death after a heart attack than depressed people who have a good support network. High levels of social support--what researchers have dubbed "the psychotherapy of everyday life"--appear to blunt depression's effect on mortality.

Indeed, people with only a small network of family and friends have a two- to three-fold greater risk of developing heart disease over time, studies say, and those who don't believe they have any emotional support whatsoever appear even worse off. Research on monkeys, who are very social animals, has shown that those who are isolated have more advanced atherosclerosis than those housed in groups.

As with depression, scientists believe that people with few social ties may be more likely to follow an unhealthful lifestyle. And again, they may also secrete higher levels of stress hormones than others.

When different types of stress converge
The different stresses in life often overlap. And when that happens, heart-disease risk rises more. Depression and anxiety are two stresses that have shown such a synergy in studies, as have stresses arising from situations like divorce or a taxing job in combination with social isolation. As Dr. Rozanski noted in a review of the phenomenon, stresses that occur in combination "substantially magnify" heart-disease risk--to an extent similar to that posed by high blood cholesterol, high blood pressure, and other major risk factors.

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