Depression has long been linked to an increased risk of heart disease. It has been speculated that the complex physiological consequences of depression might be responsible for this increase in risk. However, it seems that poor health behaviors, such as lack of exercise, largely explained the association between depression and heart disease, according to a new study published in the Journal of the American Medical Association.

Doctors from the VA Medical Center in San Francisco and their colleagues recruited 1017 patients with stable heart disease and followed them for an average of 4.8 years. The doctors used statistical models to evaluate the extent to which depressive symptoms were associated with cardiovascular events, such as heart failure, heart attack, stroke, transient ischemic attack (or, mini-stroke), and death. They found that that rate of cardiovascular events was over 30% higher among the 199 participants with depressive symptoms compared to the 818 participants without depressive symptoms. They further found that when poor health behaviors, particularly physical activity, were factored into their analysis, the association between depression and cardiovascular disease was no longer statistically significant. This demonstrated that these poor health behaviors were responsible for this association between depression and cardiovascular disease.

Patients who are depressed are less likely to adhere to their medications and more likely to smoke or be physically inactive. Previous clinical trials have looked at the use of antidepressant medications to improve outcomes in heart disease. The findings of this trial suggest that increasing exercise among depressed patients may have a positive effect on heart disease.