Dozens of studies have found an association between depression and increased morbidity and mortality in patients with acute coronary syndrome, but national health organizations have yet to formally recognize depression as a risk factor for poor outcomes. Now a group of experts brought together by the American Heart Association (AHA) has issued a scientific statement urging the association to elevate depression to the status of an official risk factor.
Published in the AHA journal Circulation in February, the statement summarizes the findings of an extensive literature review. Despite heterogeneity in patient demographics and other variables in the 53 individual studies and four meta-analyses reviewed, the preponderance of evidence links depression and adverse medical outcomes in patients following heart attacks and unstable angina.
"When something is identified as a risk factor, there's usually more attention paid to it — more of an effort to screen for it and decide the best approach to treat it," says psychologist Robert M. Carney, PhD, a professor of psychiatry at the Washington University School of Medicine, who was one of the statement's co-authors. "At the very least, there's a recognition the individual is at higher risk for morbidity and mortality."
After reviewing the individual studies, the AHA group summarized the results according to outcome:
- All-cause mortality. Most of the evidence suggests that depression is a risk factor for death from all causes in patients with acute coronary syndrome, although the authors note that some studies show no relationship between depression and death or have mixed results.
- Cardiac mortality. Although not many studies have specifically examined the relationship between depression and cardiac death and results have been mixed, most of the evidence suggests that depression is a risk factor for cardiac mortality in patients with acute coronary syndrome.
- Composite of mortality and nonfatal events. In studies that used combined endpoints of cardiac or all-cause death plus nonfatal cardiac problems, the preponderance of evidence also suggests that depression is a risk factor.
The meta-analyses followed the same pattern, showing an association between depression and poor outcomes. Based on those meta-analyses, it's safe to describe depression as a moderate risk factor, Carney says.
"If you're depressed, you're generally two to three times as likely to die or have a cardiac event in the course of follow-up," he says, adding that the relationship between depression and heart problems probably goes both ways, with depression increasing risks of cardiac problems and illness increasing risks of depression. "Depression is somewhat below smoking as a risk factor, but certainly as important as obesity and some of the other moderate risk factors."
Of course, adds Carney, it's still too soon to confirm that depression causes worse outcomes, despite the robust association the literature shows between the two.
"We can't say causal because we have not demonstrated that treating depression improves outcomes or survival," says Carney.
There has been only one study sufficiently strong enough to show the impact of depression treatment on subsequent heart attacks and death among heart attack patients — the Enhancing Recovery in Coronary Heart Disease Patients (ENRICHD) trial, published in the Journal of the American Medical Association in 2003. That study found no impact, although Carney adds that he and the other researchers in the trial identified limitations — including the small difference between the intervention and control groups after depression treatment — that could explain that lack of an effect.
Proving that treating depression improves medical outcomes in heart patients is the field's "holy grail," says psychologist Robert Allan, PhD, co-author of the 2011 APA book "Heart and Mind: The Practice of Cardiac Psychology." "If you could actually reduce recurrent cardiac events, that would be a mammoth achievement," says Allan, a clinical assistant professor of psychology in medicine at Weill Cornell Medical College.
The AHA scientific statement offers several suggestions for future research. In addition to calling for randomized controlled trials to determine whether depression treatment improves survival and other outcomes, the authors offer recommendations that include the following:
- Investigating the biological and behavioral factors involved in the relationship between depression and cardiac outcomes.
- Exploring depression's role in heart failure and other forms of heart disease.
- Assessing the impact of anxiety and other psychological problems.
- Assessing the risks and benefits of routine depression screening for heart patients.
In the meantime, says Allan, more psychologists need to start working with heart patients.
"We need to get legions of psychologists out there into hospitals and cardiac rehab centers, identifying patients who are depressed and figuring out how to treat them," he says.
- Allan, R., & Fisher, J. (2011). Heart and Mind: The Practice of Cardiac Psychology, Second Edition. Washington, D.C.: APA.
- Lichtman, J. H., Froelicher, E. S., Blumenthal, J. A., et al. (2014). "Depression as a risk factor for poor prognosis among patients with acute coronary syndrome: Systematic review and recommendations: A scientific statement from the American Heart Association." Circulation, published online.
- Behavioral Cardiology/Cardiac Psychology Listserv. This Listserv is an informal digest of cardiac psychology and behavioral cardiology research and news. Subscribe.
- "Heart and Mind: Cardiac Psychology." This APA Clinician's Corner video-on-demand, offers a three-hour overview of cardiac psychology by Robert Allan, PhD.
- "Heart and Mind: Contemporary Issues in Cardiac Psychology." This five-part video-on-demand program from APA, highlights the critical role of psychological science in understanding, preventing and treating cardiac events.
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