Relatively consistent point prevalence rates of depression have been documented in patients with CAD, ranging from 15 to 23 percent, despite the potential methodologic weaknesses of some of the studies (such as the use of unmodified psychiatric diagnostic instruments to determine the prevalence of depression, excluding patients because of CVD severity, and measuring depressive symptoms at different times after hospital admission) and methodologic differences (dissimilar patient populations, diagnostic instruments, etc.).

Although the prevalence of depressive symptoms in patients after coronary artery bypass graft (CABG) surgery, or those hospitalized for CHF, has not been as well studied, preliminary evidence indicates that these patients have equally as elevated, or even greater, rates of major depression.

The presence of depression in patients with preexisting cardiovascular disease is a risk factor for future cardiovascular events and death. The seminal studies of Frasure-Smith and colleagues demonstrated that post-MI depression was a significant predictor of mortality (p < .001) in 222 patients both 6 and 18 months after an MI.

Depression remained a significant predictor of mortality (p=.01) even after multivariate statistical methodology was used to factor out the effects of left ventricular dysfunction and previous MI. Multiple logistic regression analyses revealed that depression was significantly related to 18-month cardiac mortality even after controlling for other significant multivariate predictors of mortality [previous MI, Killip class, frequency of premature ventricular contractions (PVCs) (p= .003)]. More recent studies have been consistent with these results. Indeed, in a cohort of 870 post-MI patients recruited between 1991 and 1994, the greater the severity of depressive symptoms during the index hospital admission, the more severely diminished the long-term (5-year) cardiac mortality, independent of established prognostic factors. Depression severity had as great an impact upon survival as left ventricular dysfunction or diabetes. Other investigators have subsequently extended the finding of depression’s negative impact on prognosis to patients with CHF and patients who are post-CABG.

Despite these findings, however, other investigators have been critical of the association between post-MI depression and mortality given the possible confounding effect of severity of CVD. Although many positive studies have taken the confounding effects of disease severity into account through multivariate analysis, including the seminal studies of Frasure-Smith et al., or by making adjustments for surrogate markers of disease severity such as fatigue and dyspnea, Carroll and Lane have urged caution when using these multivariate techniques, given the possibility of underadjustment for confounding risk factors.