This is the first systematic review of the literature examining the prevalence of depression after AMI with data on more than 14,000 patients. Based on 10,785 patients assessed using a structured clinical interview, major depression was present in approximately 1 of 5 patients hospitalized for AMI. Based on 2,273 patients assessed using a BDI20
score ≥10, approximately 1 of 3 patients hospitalized for AMI had “at least mild-to-moderate symptoms of depression.” A lower prevalence of depressive symptoms meeting threshold criteria suggesting clinical significance was reported in studies using the HADS,21
for both thresholds designating “possibly
clinically significant depression” (≥8; approximately 1 in 6 patients) or “probably
clinically significant depression” (≥11; approximately 1 in 13 patients). Only 4 studies reported the proportion of patients with major depression or clinically significant symptoms of depression during the AMI hospitalization that remained depressed after hospital discharge. In these studies, which included 1,107 patients during the AMI hospitalization and 912 patients at follow-up, depression during the AMI hospitalization persisted in about half to two-thirds of initially depressed individuals in the first 1 to 12 months after discharge. The 19.8% prevalence of depression in patients hospitalized for AMI is higher than the possibly conservative rate of major depression in the general population as reported by the National Comorbidity Study (5%),58
in primary care (5% to 10%),59
or in other inpatient medical settings (6% to 14%).59
It is closer to the prevalence rates reported among patients with a stroke (20% to 30%).60–63
The reported prevalence of depression using a structured clinical interview (19.8%) was higher than the prevalence of possible (15.5%) or probable (7.3%) clinical depression using the HADS and lower than the prevalence of “at least mild-to-moderate symptoms of depression” using the BDI (31.1%). These differences do not appear related to population characteristics, which were similar across all assessment method groups (), or to sample size, regional differences, or evidence quality. These discrepancies appear to reflect some of the challenges in evaluating symptoms of depression among patients hospitalized with acute medical illness. Somatic symptoms used to diagnose depression can be difficult to distinguish from symptoms secondary to medical illness or its treatment.15,64–66
Koenig et al.66
documented similar variability in the reported prevalence of depression among medically ill patients based on characteristics of the method of assessment.
states that symptoms “accounted for by a general medical condition” should not be counted toward a diagnosis of major depression. There are no explicitly defined paradigms, however, for determining the origin of somatic symptoms. Thus, whether to attribute them to depression or not is typically left to interviewer judgment. The HADS does not include any questions about somatic symptoms.68
By contrast, 7 of the 21 items on the BDI assess somatic symptoms of depression with no reference to origin.20
It is therefore not surprising that the prevalence of possible or probable clinical depression using the HADS was lower than either the prevalence of major depression with a structured clinical interview or the prevalence of potentially significant depressive symptoms as assessed by the BDI.
Limitations of this review include the wide variations in the designs of the studies from which data was synthesized. Although results were relatively homogeneous within assessment modalities and threshold criteria, there was marked heterogeneity in study size, in-hospital and follow-up assessment timing, symptom duration criteria utilized, and diagnostic inclusiveness in studies that used standardized interviews. In addition, the review did not include abstracts, nonpublished studies, or studies published in non-English language journals. Although there does not appear to be a relationship between prevalence and sample size of the studies, we cannot rule out selection biases.
There are several reasons why it seems appropriate to screen for depression during the AMI hospitalization. Depression may have a greater effect on quality of life and physical limitation in patients with coronary disease than traditionally determined measures of cardiac function.69
This effect is likely to persist for at least several months, since depression that is present during the AMI hospitalization does not resolve in a substantial proportion of patients based on the few studies that have addressed this issue. Depression would be important to identify in AMI patients if it were shown that patients should be treated differently than those who are not depressed. For example, patients with depression after AMI have increased platelet activation70
and poor adherence to recommended therapy,71
raising the possibility that these patients should receive more aggressive antiplatelet therapy or focused adherence-enhancing initiatives. Although the effect of these strategies has not yet been examined, proper identification of patients with depression during the AMI hospitalization is critical if these questions are to be appropriately addressed. Some have argued that depression should be identified during the AMI hospitalization because depressed patients have a higher risk of morbidity and mortality after AMI.1,2,4
Two recent large, randomized controlled trials assessed whether treatment of depression affects prognosis in AMI patients with depression,33,72
and neither definitively demonstrated that treatment of depression alters cardiovascular prognosis of AMI patients. It would be unfortunate if these results were to lead health care providers to turn their attention away from depression in the AMI setting, however, as it is widely accepted that depression is common and underrecognized in many clinical settings. A patient hospitalized for AMI provides an opportunity for the diagnosis and treatment of health conditions other than the individual's cardiac condition.
This systematic review suggests that if clinicians assess for symptoms of depression as endorsed by AMI practice guidelines,13
results will differ considerably depending on method of assessment. It appears reasonable to screen patients with a validated questionnaire, and then to assess patients who screen positive using a structured clinical interview. This assessment can be further refined by re-examining the patient several weeks after discharge. At first glance, based on reported prevalence rates alone, it would appear that the BDI is a more appropriate initial screening instrument than the HADS as it identifies more potentially depressed patients during the AMI hospitalization, a desirable quality in a screening instrument. Although a BDI score of 10 or above may overdiagnose depression, evidence suggests that patients with BDI scores at or above this threshold soon after an AMI have higher morbidity41
risks than those patients who endorse fewer symptoms of depression on this questionnaire. These findings, coupled with the “dose response” of BDI scores as predictors of risk after AMI3,6
suggest that the BDI is the preferred mode of assessment in this setting. We believe that further research studies are warranted to compare the performance characteristics of the BDI to other depression screening instruments in patients who are hospitalized with AMI; to assess whether alternative assessment methods, such as administering only the nonsomatic items on the BDI, produce improved results; and to examine which patients so identified are likely to remain depressed after discharge from the hospital. Until these studies are performed, we suggest that clinicians consider using the BDI when following current practice guidelines that recommend assessing patients for symptoms of depression after an AMI.13
Patients who score 10 or above on the BDI should then be evaluated by a clinical psychologist or psychiatrist.
Although this systematic review did not address the ideal timing of post-AMI depression screening, a reasonable strategy would be to use the BDI during the initial hospitalization when the patient is readily accessible. If a patient has symptoms of depression (BDI ≥10), the possibility that depression may impact the patient's recovery could be discussed with the patient and other appropriate individuals in collaboration with the patient. If the patient notes that negative emotions are adversely affecting self-care and ability to function or if the patient has thoughts of self-harm, a referral to a mental health provider should be facilitated. In cases where an immediate referral is not made, the patient could be reassessed by BDI screening 2 weeks after discharge. If the patient still scores ≥10, referral to a mental health provider for a formal assessment should be arranged; somatic symptoms present at this point should be assumed to be related to depression rather than to the patient's cardiac condition, particularly if the cardiologist indicates that the latter has stabilized.