Depressive disorders are common following an acute myocardial infarction (AMI), occurring in 15 to 20 percent of patients. The risk of death following AMI is increased with clinically significant depression, defined as a Beck Depression Inventory score of 10 or higher. This increased risk is independent of other risk factors such as low left ventricular ejection fraction (LVEF), age, or history of AMI. Bush and associates looked at the effect of minimal depression (Beck score lower than 10) on mortality risk after AMI.

In a prospective cohort study, 271 patients admitted to a community hospital with the diagnosis of AMI were tested for mood disorder with the Structured Clinical Interview for DSM-III-R and for depression using the Beck inventory. A follow-up was done by telephone at four months. Increased four-month mortality occurred in patients older than 65 years and those with diabetes, a history of coronary artery disease, prior AMI, and decreased LVEF. Patients (some of whom had evidence of mood disorders) with Beck scores of 10 or higher had a four-month mortality of 13.2 percent compared with 5.1 percent in those with Beck scores lower than 10. The latter mortality risk was higher than that in patients without mood disorder or significant clinical depression (3.8 percent) as represented by a Beck score of higher than 10.

The authors conclude that low levels of depressive symptoms that may not be evident on Beck inventory testing may increase mortality risk following AMI. Mortality risk associated with depression was found to increase with the extent of depressive symptoms. In patients older than 65 years with a Beck score of zero to 3, the mortality rate was 2.6 percent. For scores of 4 to 9, and 10 and higher, the mortality rates were 17.1 and 23.3 percent, respectively. Because the greatest mortality in this study occurred in patients older than 65 years, further work is needed to confirm the results and learn whether the increased mortality risk related to low levels of depression following AMI is limited to older adults.