People who are diagnosed with coronary artery disease and then develop depression face a risk of death that’s twice as high as heart patients without depression, according to a major new study by researchers at Intermountain Healthcare in Salt Lake City.

The increased risk of death from any cause holds true whether the depression immediately follows the heart disease diagnosis or occurs even years later, according to Heidi May, PhD, a cardiovascular epidemiologist at Intermountain Medical Center Heart Institute and the study’s lead author.

She said the findings point out the importance of screening for and treating depression even years after someone is diagnosed with heart disease.

The research, one of a number of studies to explore the connection between heart disease and development of depression by researchers at Intermountain Medical Center Heart Institute, was published on July 28th in The European Heart Journal – Quality of Care & Clinical Outcomes.

“Depression was the strongest risk factor for dying, compared to any other risk factors we evaluated. That included age, heart failure, diabetes, high blood pressure, kidney failure, or having a heart attack or stroke,” Dr. May said.

That association didn’t change for patients who were previously diagnosed with depression before their heart disease diagnosis or for patients whose angiograms were performed for various reasons, which included stable angina, unstable angina, or heart attack.

Dr. May and the Intermountain Medical Center Heart Institute research team studied 24,138 patients who underwent angiographies, which determined they had coronary artery disease. To detect subsequent depression, the researchers looked at standardized diagnostic codes called International Classification of Diseases codes, or ICD codes.

Patients with depression were also placed into subcategories based on how long after their heart disease diagnosis the depression was identified.

In all, 15 percent, or 2,646 patients, were diagnosed with depression at some point during follow–up. Of those, 27 percent were diagnosed within a year of their heart event, 24 percent between one and three years after, nearly 15 percent between three and five years after, and nearly 37 percent at least five years after a baseline heart disease event.

Research has shown that the relationship is bi–directional: Depression may result in worse outcomes for people with heart disease, while the presence of heart disease may increase the likelihood that someone will develop depression.

Those with depression were significantly younger and more often female, diabetic, previously diagnosed with depression, and less likely to have presented with a heart attack compared to those who didn’t have depression.

“We know people with depression tend to be less compliant with medication on average and probably in general aren’t following healthier diets or exercise regimens,” she said. “They tend to do a poorer job of doing things that are prescribed than people without depression. That certainly doesn’t mean you’re depressed so you’re going to be less compliant, but in general, they tend to follow those behaviors.”

She also noted that physiological changes occur within the body when patients are diagnosed with depression, which might help explain the link.

The researchers emphasize the importance of continual screening of depression for all heart disease patients. “Patients who have depression need to be treated for it to improve not only their long–term risks but their quality of life,” Dr. May said.