FRIDAY, Aug. 1, 2008 (HealthDay News) -- Scientists have long observed a link between depression and heart disease. Now there's research to help pinpoint the symptoms of depression that may signal cardiovascular trouble.

A study suggests that people who suffer from depression, especially certain physical symptoms such as loss of appetite, sleep problems or fatigue, may be at risk of developing heart disease.

"Our findings raise the possibility that the physical symptoms of depression are particularly toxic to the cardiovascular system," said the study's lead author, Jesse C. Stewart, assistant professor in the Department of Psychology at Indiana University-Purdue University, Indianapolis. "Identifying the most harmful aspect of depression is important, because we will then know which specific components to target with our treatments."

Previous studies have linked negative emotions, including depression, anxiety and anger, to a heightened risk of heart disease. But because these emotions tend to overlap and "co-occur" within people, it's been difficult to associate a particular symptom -- or set of symptoms -- with heightened cardiovascular risk, Stewart explained.

His study, published in the Archives of Internal Medicine, is believed to be the first to tease out which emotions are key risk factors for heart disease.

"Our study is important, because it is the first to simultaneously examine the links between all of these negative emotions and sub-clinical atherosclerosis," Stewart said. "In addition, we broke depression down into physical and cognitive/emotion symptom clusters, which is uncommon."

Stewart's team measured the internal carotid artery thickness of 324 adults at the beginning of the study and three years later.

Thickening of the inside walls of the coronary arteries -- atherosclerosis -- slows or blocks the flow of blood to the heart and brain and can lead to heart attack or stroke. The carotid artery is the large vessel in the neck that supplies blood to the brain.

The study found that depressive symptoms, but not anxiety and anger, were associated with greater thickening of the arteries over time. Further analyses indicated that only the physical symptoms of depression were associated with thickening arteries, while the cognitive and emotional symptoms of depression, such as sadness, pessimism, and indecisiveness, were not related.

Scientists have not yet established whether depression causes heart disease or whether some other factor, such as diet, affects depression and heart disease. In a review of the epidemiologic data, published in 2007, Dr. Francois Lesperance, a professor in the Department of Psychiatry at the University of Montreal in Canada, noted that the evidence supports each theory.

While it might be useful to identify depression as a marker for future heart trouble, it's still not a proven tool. "No secondary prevention trial has successfully reduced cardiovascular risk by targeting depression," Lesperance wrote.

Robert M. Carney, a professor of psychiatry and director or the Behavioral Medicine Center at Washington University School of Medicine in St. Louis, agreed. "There currently exists no evidence that treating depression will help prevent heart disease," he said. "The biggest reason is that studies that would be needed to draw that conclusion would have to be large and therefore very expensive."

Still, Carney thinks it's important for patients to know that depression is a risk factor for developing heart disease. What's more, the potential benefits of recognizing and treating depression, such as improved quality of life, are well known and sufficient reason to get treatment, he noted. "Hopefully, an added bonus will be to reduce the risk of developing or suffering from heart disease," he said.

Stewart is planning other studies examining the relationships between depression and hostility, and various measures of cardiovascular risk. He also plans to investigate whether positive emotions -- happiness, for example -- and related factors, such as optimism, are associated with reduced cardiovascular risk and therefore protective against heart disease.

"Ultimately, we plan to use the data from this study and similar investigations to develop a psychological treatment for adults at risk for cardiovascular disease," Stewart said. "We hope that our treatment, when combined with standard treatments, will help to prevent the development of cardiovascular disease."

More information

For more on depression and related health risks, visit the National Institute of Mental Health.

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