Studies indicate that 14 to 47 percent of patients with coronary artery disease have significant comorbid depression and that the highest incidence occurs in patients awaiting coronary artery bypass graft (CABG) surgery. Depression also has been identified as a significant risk factor for morbidity and mortality in patients with coronary artery disease. Blumenthal and colleagues studied the association between depression and mortality in patients undergoing CABG.

The authors recruited 817 patients scheduled for CABG at a large university center between 1989 and 2001. Patients with a history or current evidence of a psychiatric illness, including depression, were excluded from the study. Patients also were excluded if they had serious concomitant medical conditions. Patients were assessed for depression on the day before surgery using a standardized 20-item scale. This assessment was repeated after six months and at regular intervals for up to 12 years.

The average age of the 221 women and 596 men was 61 years. Almost 90 percent of participants were white. The median follow-up time was five years. Before surgery, 310 patients (38 percent) had clinical depression. Depression was significantly more common in women, and the incidence was inversely related to age. Patients with depression did not differ from other patients in ethnicity or incidence of diabetes, obesity, left ventricular dysfunction, or tobacco use. The two groups of patients also were comparable in the number of grafts and history of myocardial infarction.

During follow-up, 122 patients (15 percent) died. Patients with moderate or severe depression had increased risk of mortality. The adjusted hazard ratio was 2.4 for moderate to severe depression and 2.2 for mild or moderate depression. Patients who were depressed before surgery but not depressed at the six-month follow-up had the same mortality rate as patients who were never depressed. The relationship between mortality and depression was not significantly altered by statistical adjustment for all important variables. Overall, 19 percent of patients who were persistently depressed died compared with 10 percent of patients who were never depressed.

The authors conclude that moderate to severe depression persisting after CABG is associated with increased mortality. Because 58 percent of patients who had moderate to severe depression before CABG had persistent depression following surgery, the authors call for increased awareness of the need to detect and treat this comorbidity.