In a three-year study of 5,000 patients suffering from moderate to severe depression, those treated with antidepressants showed lower rates of death due to coronary artery disease and stroke compared to those who did not take the medication.

For the study, researchers identified over 5,000 patients suffering from depression that were treated by the Intermountain Medical Center Heart Institute over 3 years. The screening of the patients asked about factors such as mood, sleep and appetite to gauge the level of depression.

Lead author, Heidi May PhD, a public health scientist, says that "this study demonstrates the importance of evaluating patients for depression, not only in terms of improving their mood, but reducing their risk for heart disease."

Researchers discovered that the rates of coronary artery disease and stroke versus levels of depression were lower in patients suffering from depression that were given antidepressants compared with those who were not given the treatment.

"Antidepressants were not associated with a reduced cardiovascular risk in people with little or no depression, but in moderately to severely depressed people, antidepressants were shown to significantly improve cardiovascular outcomes," May says.

Although the study was not designed to analyze a correlation directly, moderately to severely depressed patients taking antidepressants alone, the researchers say, appeared to fare better than those taking statins alone or in addition to the mental health drugs.

"We thought we'd see an additive effect," May says. The researchers found, however, "that in the more depressed people, the antidepressant really was what made the biggest difference."

Dr. May believes treating depression results in behavioral changes that could explain the links suggested by the limited epidemiological study.

"Antidepressants might have relevant physiological benefits, but I also think the behavioral changes that improve a person's mood can also improve cardiovascular health" May says. "This study demonstrates the importance of evaluating patients for depression, not only in terms of improving their mood, but reducing their risk for heart disease."

The research took into account the effects of standard cardiovascular risk factors such as diabetes, smoking and high blood pressure in drawing a correlation with antidepressants.  However, because the study focused only on data found in medical records, the research could not account for other factors that might have explained the association with the drug treatment for depression, including physical activity, changes in lifestyle, or nondrug mental health treatments such as counseling.

The study will be presented on March 15 at the 64th annual scientific session of the American College of Cardiology in San Diego, CA.