Biomedical studies have repeatedly proved that people with mood disorders have high death rates from cardiovascular disease. Current research is building on this knowledge with new insights.

A recent Duke study revealed that heart patients with mild to moderate depression are highly susceptible to the stresses of everyday living on the heart. Another suggested that depression's damaging effects on the heart are even more pronounced in women.

Treating depression seems to improve the heart's health. Among former heart attack patients, antidepressants have been associated with a dramatic reduction in death or heart attack recurrence. Because regular exercise improves mood, it may also be very helpful for depressed heart patients.

Cardiovascular disease may, in turn, cause cerebral "mini-strokes" that can contribute to depression in the elderly. So taking steps to protect either mental or heart health will likely offer beneficial effects on both.

Depression and Heart Disease: Close Connections

Can sadness break your heart? A growing body of research suggests that the long-celebrated link between feelings and the heart is more than a poetic notion. In fact, it may not be long before the treadmill stress test is joined by an emotional stress test -- one that measures depression, hostility, and anxiety -- as a standard cardiovascular screening tool.

Cardiovascular disease is the leading cause of death in the United States, affecting about 13 million Americans and killing more than half a million of us each year. "We've known for decades that people with mood disorders have high death rates from cardiovascular disease," says Duke cardiologist Christopher O'Connor, MD. In ongoing studies, O'Connor and several Duke colleagues continue to build on that knowledge with new insights.

Recently, Duke researchers discovered that heart patients with mild to moderate depression are highly susceptible to the stresses of everyday living on the heart. These patients, says study author Wei Jiang, MD, are more likely to experience ischemia, or reduced blood flow to the heart muscle. The condition often damages the heart without causing symptoms and, over time, can lead to chest pain, heart attacks, or death.

According to a landmark study led by Duke psychologist Anastasia Georgiade, PhD, depression's damaging effects on the heart are even more prevalent in women. Georgiade's work showed that female heart patients with symptoms of depression are twice as likely to die as those who don't have such symptoms.

"Although men and women have a similar mortality risk once depression occurs, women have almost twice the prevalence of clinical depression as compared to men, making depression an even more important risk factor among women," she says. For patients of both sexes who have undergone coronary artery bypass (CABG) surgery to restore blood flow to the heart, depression is especially dangerous, appearing to double the chances of death after the procedure.

Clotting, Inflammation May Play Role

The underlying reasons for the strong link between depression and heart disease are still being teased out. While depression has been linked to other risk factors such as obesity, high blood pressure, and physical inactivity, it also seems to be a potent factor on its own.

Researchers have noted that depressed people have more blood platelets that clump together, thickening blood and clogging arteries. The hearts of depressed people may also be more vulnerable to heartbeat irregularities when exposed to stress and anxiety.

C-reactive protein (CRP), a substance produced by the liver in response to inflammation, may provide another clue. Recent studies suggest that CRP is associated with inflammation developing within arteries as they become clogged with plaque. In a Duke study led by Edward Suarez, PhD, participants who scored high on tests for anger, hostility, and depression had CRP levels two to three times higher than those who scored low.

Easing Depression May Boost Heart Health

So if depression is bad for the heart, will treating it improve the heart's health? Duke studies seeking to answer that question have yet to come up with a definitive answer, but the initial findings indicate a definite 'maybe.'

The SADHART study found that heart failure patients given the antidepressant sertraline (Zoloft) had 23 percent fewer cardiovascular events than a control group. While the results may not be statistically significant, researchers are continuing to study the heart failure population, and they hope to obtain more concrete results.

Sertraline is part of a family of antidepressants known as SSRIs (selective serotonin reuptake inhibitors), which tend to reduce abnormalities in heart rhythm and blood clotting; they may also act as blood thinners in cardiac patients. According to K. Ranga Krishnan, MD, Duke's chair of psychiatry, treatment with sertraline or another SSRI is now a standard intervention for heart attack patients who are depressed.

Exercise may also be a lifesaver for depressed heart patients. According to the results of a national trial led by Duke, heart attack patients who are depressed or without social support are more than twice as likely to die of a second heart attack if they do not exercise.

"Whether they were depressed because they were sedentary or vice versa, our findings demonstrate the value of exercise in improving both the mental and physical health of these high-risk heart patients," says lead researcher James Blumenthal, PhD, a Duke behavioral psychologist. "For depressed heart patients, a prescription for exercise could be just as important as one for statins or beta blockers."

Two other common interventions for depression -- psychotherapy and counseling -- significantly improve depression and improve quality of life for heart patients. However, they have not been shown to reduce mortality from heart disease. "This may mean that there's something going on at the biochemical level," O'Connor says. "I think depression will turn out to be a risk factor for heart disease that we'll need to measure like cholesterol level."

Agrees Wei: "Given what we know about depression and heart disease in general, psychiatric screening should be a part of all cardiac workups."

Elderly Mood Disorders Linked to Stroke

Recent research by Krishnan suggests that the reverse may also be true. Investigating strange lesions known as "lacunes" in the frontal lobes of elderly patients, Krishnan found that patients with such lesions had symptoms of both depression and heart disease. Armed with high-tech imaging techniques that measure blood flow, Krishnan discovered that the origins of such lesions are small "silent" strokes deep within the brain. While causing no obvious motor, cognitive, or speech loss, these "mini-strokes" can affect mood regulation.

"These patients had all the classical risk factors for heart disease -- such as diabetes, hypertension, clogged arteries, or a history of heart surgery -- but none of the risk factors for depression," Krishnan says. "In other words, their cardiovascular risk factors gave rise to their depression."

Krishnan labeled the condition vascular or "arteriosclerotic" depression to connote the narrowing and eventual closure of small blood vessels that resulted in the silent strokes. So common is the condition that it may account for 30-40 percent of all depression in people over the age of 65.

Krishnan is hopeful that treatments to prevent vascular depression could mirror those for managing heart disease, including a low-fat, low-salt diet; blood pressure and cholesterol medications; and surgical techniques to treat atherosclerosis. But he says clinical studies are needed to confirm that, and such therapy may not reverse existing damage.

So if you're interested in living a long and happy life, and wondering whether to focus more intently on your mental or cardiovascular health to achieve that goal, take this message to heart: Taking good care of either one will very likely enhance both.