While it has long been known there is a strong association between depression and an increased risk of cardiovascular events, it has not been understood why. The Heart & Soul Study reveals the link is largely explained by behavioral factors, particularly physical inactivity.

This prospective cohort study is based on a sample of 1,017 patients who had stable coronary artery disease at the study's outset and were followed for almost five years. The patients were identified at two Veterans Administration hospitals, one university medical center and nine public health clinics. Data was developed through medical testing, interviews and self-reporting questionnaires.

Key Findings:

• Of the 1,017 participants, 199 patients (19.6%) had depressive symptoms.
• During the study, depressed patients had a 50 percent greater rate of cardiovascular events, such as heart attack or stroke. The age-adjusted rate of cardiovascular events among depressed patients was 10 percent, while it was just 6.7 percent among nondepressed participants.
• Physical inactivity appeared to account for almost half of the association (44%) between depression and cardiovascular events.
• Nearly all of the association could be tied to health behaviors, including physical inactivity, as well as smoking and not taking medication as prescribed.
• Nonbehavioral variables that had been hypothesized as potential links, such as the severity of cardiovascular disease, the use of tricyclic antidepressants, levels of serotonin and omega-3 fatty acids, were found to have little association with the increased risk of cardiovascular events for depressed persons.

This study evaluated depression and health behaviors simultaneously so it is not known whether the behaviors are the cause of depression or the result of depression; depressed patients are often less likely to take care of themselves. But, regardless, the findings do suggest behavioral modification, and in particular, increasing physical activity, could reduce the risk of cardiovascular events in depressed patients with stable coronary heart disease.