toll on the heart
A new scientific statement from the American Heart
Association identifies depression as a risk factor for heart disease.
BY REBECCA A. CLAY
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