Depression Increases Risk after Heart Disease

by Thomas S. May

September, 2005

A growing body of evidence indicates that for people with heart disease, depression can shorten life expectancy and increase the risk of additional cardiac events. Therefore, researchers have suggested that people with heart disease be screened for depression and treated with antidepressant medication and/or psychotherapy if necessary.

Although the evidence is not conclusive, results of recent studies indicate that, in addition to relieving depression, some antidepressants may actually help prolong the lives of cardiac patients.

Lethal Combination

Studies have consistently shown that, among patients who have had a heart attack, the risks of additional cardiac events are about two to three times higher for those who have depression, says Daniel Ford, a professor of medicine, psychiatry, and epidemiology at Johns Hopkins University.

Ford notes that several mechanisms appear to account for the increased risk brought on by depression. “Part of the reason is that individuals with depression are less likely to follow recommendations to reduce the risk, like stopping smoking, taking aspirin, or increasing exercise,” he says.

“Another reason is that individuals with depression have stickier platelets, and this leads to more clots and blockages in the arteries,” Ford adds. “Yet another reason may be that the changes in the brain from depression affect the regulation of the heart through the parasympathetic and sympathetic nerves leading to the heart.”

Glen Xiong of Duke University Medical Center in Durham, N.C., thinks depression disrupts the delicate balance of brain chemicals such as dopamine and serotonin, and alters the body’s “fight-or-flight” response, adversely affecting the cardiovascular system.

Depression is also associated with increased cortisol levels. “Cortisol is released from the adrenal cortex in response to stimulation by the pituitary gland inside the brain,” Xiong explains. “An overproduction of cortisol suppresses the immune system, which has a negative effect on the cardiovascular system.”

Scientists believe that depression is responsible for lower survival rates in people with heart disease. © CORBIS, Creator Maria Rendon.

Heart Disease and SSRIs

In a recent study, Xiong and colleagues analyzed the medical records of nearly 5,000 heart surgery patients who had been operated on at Duke between 1999 and 2003. The researchers found that patients who had been taking selective serotonin reuptake inhibitors (SSRIs), a class of antidepressant medication, had lower survival rates in the following four years (75 percent), compared with those who had not been taking SSRIs (85 percent).

The scientists believe that the lower survival rates were caused by the patients’ underlying depression, not the medication. In fact, several studies indicate that SSRIs are helpful for cardiac patients who suffer from depression.

The first trial that investigated the effects of SSRIs in patients with both cardiovascular disease and depression was the Sertraline Anti-Depressant Heart Attack Trial (SADHART). Scientists found that the incidence of severe cardiac events (death, heart attack, congestive heart failure, stroke, and recurrent angina) was lower among patients receiving SSRIs (14.5 percent) than among those receiving a placebo (22.4 percent).

Another study, called ENRICHD (Enhancing Recovery in Coronary Heart Disease), examined the effects of cognitive behavioral therapy in patients who were clinically depressed after they had suffered a heart attack. The investigators found that the therapy significantly reduced depression but had little effect on mortality rates.

However, a secondary analysis of the data showed that 26 percent of participants who had not received antidepressants died or had a recurrent heart attack, while only 21 percent of those who had taken antidepressants died or had another heart attack. After adjusting for baseline depression and cardiac risk, SSRI use was associated with a 43 percent lower risk of death from all causes.

These results indicate that depression should be treated aggressively in patients with heart disease, says Robert Carney, one of the investigators. “It is important to treat depression, because even a few depression symptoms seem to increase the risk of cardiac events.”