Major depressive disorder (MDD) is the most commonly diagnosed psychiatric disorder among American adults, with lifetime prevalence rates of up to 25% in women and 12% in men, and point prevalence rates of 6% in women and 3% in men.1 These gender differences are relatively constant over adulthood, although there is evidence that the prevalence of MDD is increasing and the age of first onset is decreasing. Major depressive disorder is even more common among patients with coronary heart disease (CHD), with estimates ranging from 16% to 27%, and an additional 20% to 30% of cardiac patients with minor depression (mDD) or elevated depressive symptoms.2 Major depressive disorder is best diagnosed by a psychiatric interview. To meet criteria for MDD, a patient must report sad or "depressed" mood or a significant loss of interest in all or most things that were previously considered enjoyable for a minimum of 2 weeks, and at least an additional 4 (or 3, if both dysphoric mood and loss of pleasure are present) of the following symptoms: significant weight loss or change in appetite, insomnia or hypersomnia, psychomotor agitation or retardation, fatigue or loss of energy, feelings of worthlessness or excessive guilt, decreased concentration or indecisiveness, and recurrent thoughts of death or suicidal ideation. Minor depression (mDD) is not yet an official psychiatric diagnosis, but rather is a clinical syndrome often used for research purposes. Its features are similar to MDD, but with fewer depressive symptoms and less impairment. An episode of mDD involves either a sad or depressed mood or loss of interest or pleasure in nearly all activities, and a total of at least 2 but less than 5 additional depressive symptoms. Dysthymia is marked by a chronically depressed mood state for at least 2 years. At least 2 additional depressive symptoms are present without meeting criteria for MDD. Self-report instruments such as the Beck Depression Inventory (BDI), Zung Depression Scale, or the Center for Epidemiological Studies of Depression Scale (CES-D) can also reliably assess depressive symptoms, although questionnaires cannot diagnose MDD and should not be considered a substitute for clinical interviews for diagnostic purposes.

In this issue of the journal, Todaro and colleagues report that more than 20% of patients enrolled in cardiac rehabilitation (CR) met criteria for a current depressive disorder, including 9.1% for MDD, 6.4% for mDD, and 5.5% for dysthmia. These figures may be somewhat lower than expected, based on previous reports.2 However, the lower estimates may be attributable to the relatively small sample size, selective enrollment (only 82% of eligible CR participants agreed to undergo the psychiatric assessment), and use of an unfamiliar instrument, the Anxiety Disorders Interview Schedule, for the diagnosis and severity rating of depression. In addition, it is possible that patients who are referred for CR-and more importantly, follow through with the referral-may not be representative of the general cardiac population. Indeed it has been shown that patients with depression are less likely to adhere to prescribed medical therapies, including participation in CR services.3 More striking, however, was the prevalence of depression among female patients, with 43% of female CR participants meeting criteria for depressive disorder during their lifetimes compared with only 19% among males. Furthermore, almost 29% of women in the study met criteria for a current depressive disorder compared with only 9% of men.

These are sobering figures and are significant for a number of important reasons: depression takes a devastating toll on patients' quality of life; adversely affects marital and social relations; results in increased use of social and medical services; is associated with more days in bed or days away from normal activities; and is responsible for enormous financial costs for treatment, lost productivity, and absenteeism from work. In addition, there is mounting evidence that depression is associated with worse prognosis, with a 2- to 5-fold increase in relative risk in patients suffering an acute myocardial infarction (MI),4 congestive heart failure,5 and post-coronary artery bypass surgery.6 Moreover, mDD, dysthymia, and even subclinical depression as measured by elevated scores on self-report instruments such as BDI and CES-D scales are associated with increased risk.2 Thus, not only recognizing depression but also successfully treating it has become a priority.

Several recent studies have assessed the extent to which depression can be successfully treated in cardiac populations. Selective serotonin reuptake inhibitors (SSRIs) are widely considered to be safe for patients with CHD. For example, the SADHART study showed that sertraline did not adversely affect cardiac function and was safe for most patients.7 While non-significant or modest reductions in depressive symptoms were noted in the sample as a whole, evidence suggested that treatment was effective for patients with recurrent or more severe depression.

There is also great interest in nonpharmacological approaches to treatment. Behavior therapy, cognitive behavior therapy (CBT), and interpersonal psychotherapy all have been shown to be efficacious in treating depression in healthy, depressed populations without CHD. In addition, the ENRICHD trial recently showed that similar to antidepressant medication, CBT is modestly effective in reducing depression in acute post-MI patients.8 Evidence suggests that exercise therapy also may be an effective treatment for depression,9 and exercise after an acute MI has recently been reported to be associated with significantly reduced morbidity and mortality among patients with MDD,10 suggesting that exercise is a promising intervention for patients with CHD and depression.

It remains to be seen whether treating depression may reduce risk of adverse events in depressed CHD patients. Although the ENRICHD trial failed to demonstrate that reducing depression improved survival, antidepressant use was actually associated with better clinical outcomes, independent of the effects on depression. Additional randomized controlled trials need to be undertaken with cardiac patients who are depressed to examine efficacy for psychosocial and "hard" clinical endpoints. It should be noted that because of improvements in the surgical and medical management of patients, it is possible that treating depression may not reduce significantly the risk of death or reinfarction over and above standard risk factors such as CHD severity and the presence of medical cormorbidities. Nevertheless, depression remains a highly prevalent and insidious comorbid condition in cardiac patients and needs to be recognized and treated, if not to prolong life then certainly to enhance patients' quality of life.

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