Researchers found otherwise healthy people prone to anger, hostility, and depression have higher levels of a substance linked to narrowing of the arteries and future heart disease risk called C-reactive protein (CRP). This protein is released in the body in response to the inflammation caused by stress, infection, and other threats to the immune system.
Researchers say the findings show that these behavioral and psychological factors might help account for the 50% of heart attacks that occur among people without any of the traditional risk factors for heart disease.
"These psychological behaviors do have implications in determining health or the risk of disease that we have," says researcher Edward Suarez, PhD, associate professor of psychiatry and behavioral sciences at Duke University Medical Center.
"This is the first study to show there is an independent association between depression and C-reactive protein," Suarez tells WebMD, "regardless of their weight, blood pressure, [cholesterol] levels, alcohol use, and exercise status."
C-Reactive Protein Tied to Depression
In the study, published in the September issue of Psychosomatic Medicine, 127 healthy men and women completed personality questionnaires that assessed anger, hostility, and depressive symptoms. Blood tests were then performed to measure CRP levels.
The study showed that healthy adults who had mild to moderate symptoms of depression, anger, or hostility had levels of CRP, a marker of inflammation in the blood, that were two to three times higher than those of their calmer counterparts. And the more negative their moods, the higher their CRP levels were.
Suarez says that it's the clustering of anger, hostility, and depression that commonly occurs in the same individual that may produce the greatest risk. For example, people with these attributes may evaluate their surroundings in a cynically hostile way and then react with anger to events, which is then commonly accompanied by mild to moderate symptoms of depression.
Suarez explains that it may be that people prone to anger go through life and consistently react negatively to life events. In response, their bodies release stress hormones that eventually lead to an elevation in CRP.
These CRP elevations do not fluctuate as easily as hormones and are instead maintained for long periods of time, which may subsequently increase the risk of narrowing of the arteries and heart disease.
Understanding Depression and Heart Disease
Researchers say the findings may be the first step in understanding the complex relationship between psychological factors such as depression and heart disease.
"It's noteworthy that people are at last looking for mechanisms to explain the pretty well-established link between depression and heart disease," says Sylvia Wassertheil-Smoller, PhD, professor of epidemiology and population health at Albert Einstein College of Medicine of Yeshiva University in New York.
But she says it's still unclear, which direction the relationship flows, whether depression increases inflammation or if inflammation is a part of a syndrome that includes depression and other underlying processes.
"Nevertheless it's a biochemical link between depression and heart disease because we know that CRP identifies people at future risk of heart disease," Wassertheil-Smoller tells WebMD. "It is a very interesting link that needs to be pursued."
Lawson Wulsin, MD, associate professor of psychiatry and family medicine at the University of Cincinnati says this study adds to a growing body of research on the interplay between the entire inflammatory process, depression, and heart disease.
"Both depression and C-reactive protein are in the running as candidates for the next major risk factor for coronary heart disease, says Wulsin. "To show that they are linked at least in time is a step toward the process of showing that they may be linked by cause and effect or that they may be operating on the same pathway that later increases the risk for heart disease."
Researchers say the next step will be to conduct long-term studies to see if the elevated CRP levels associated with depression, anger, and hostility are associated with higher rates of heart disease over time.
Once the relationship between inflammation and psychological factors is clearly established, researchers say they can begin looking at new targets for heart disease prevention and treatment by either by targeting the psychological symptoms or the inflammation itself.