Association of higher costs with symptoms and diagnosis of depression

Physical health status (measured by the physical component score of the MOS SF-36) predicted the occurrence of all charges measured with the exception of laboratory tests. Advanced patient age predicted increased likelihood of charges in each area; female sex showed a trend toward predicting occurrence of emergency care charges; and education showed a trend toward predicting occurrence of laboratory charges. BDI scores (measure of symptoms of depression) and physician diagnosis of depression failed to contribute significantly to the prediction of specialty care, emergency care, laboratory testing, or hospital charges. However, there was a trend for depressive symptoms to predict the occurrence of laboratory charges.

The right side of Table 2 presents regression models that predicted the magnitude of the different categories of charges. Physical health status was a significant predictor of the magnitude of all types of charges except emergency care. Patient age contributed to prediction of size of all types of charges except emergency visits and laboratory tests. Female sex was a significant predictor of magnitude of charges in primary care, laboratory tests, and total medical charges. The diagnosis of depression was a significant predictor of magnitude of primary care (P = .0029) and total medical (P = .0158) charges. Neither depressive symptoms nor the diagnosis of depression contributed significantly to the prediction of magnitude of charges for specialty care, emergency care, laboratory testing, or hospital use, although there was a trend for depressive symptoms to predict the magnitude of laboratory costs. Although an interaction term was entered into both kinds of regression equations, there was no evidence of a significant contribution from the interaction of symptoms of depression and diagnosis of depression in any of the predictor models developed.

TABLE 2
Regression analyses predicting charges

Discussion

Medical charges were related to symptoms of depression and physician diagnosis of depression in this study. Although the patient sample was small, it was representative of the primary care population in displaying a wide range of depressive symptoms as measured by the BDI.^6,7 In this study, physician diagnosis of depression was related to self-reported depression ratings: those diagnosed as depressed had significantly higher BDI scores than did those not diagnosed as depressed. However, the relationship between self-reported symptoms and diagnosis was not perfect: 72% of patients with high BDI scores were not recognized as depressed, as often occurs in primary care.^6,7 In fact, more patients diagnosed with depression had low BDI scores (< 9, n = 41) than high BDI scores (> 8, n = 36). Clearly, other factors enter the process by which primary care physicians reach the diagnosis of depression.

Symptoms of depression and the diagnosis of depression probably influence the process of care in different ways. Differences in process of care likely would be reflected in different relationships to medical charges. Physician diagnosis of depression was associated with higher primary care and total costs and contributed to models predicting magnitude of primary care and total charges. However, neither symptoms of depression nor diagnosis of depression predicted which patients were more likely to incur charges for specialty care, emergency care, laboratory tests, or hospitalization. There was a trend only for the symptoms of depression to predict who would incur laboratory charges. These findings suggest that the relationship between depression and primary care charges and total charges is clear but less apparent when looking at less frequently occurring charges.

Other demographic factors showed fairly robust associations with the occurrence of charges. Patient age predicted who would get specialty care, emergency care, laboratory costs, and hospitalization, and there was a trend for female sex to predict occurrence of emergency department charges. Health status proved to be a significant predictor of the magnitude of all charges except those for emergency care. These powerful influences must be considered to accurately assess the impact of depression on charges.

Age also predicted the total amount of charges for primary and all medical care for the year and showed a trend toward prediction of magnitude of specialty charges. Female sex was a significant predictor of magnitude of primary care charges, laboratory charges, and total charges, and less education was a significant predictor of magnitude of emergency department and hospital charges. Some of these demographic predictors are readily explained. For example, as patients age, the number and costs of medical problems often increase. More education may enhance socioeconomic status and self-care, each of which may buffer against the need for emergency care and hospitalization. The reasons that charges are often higher for women are probably more complex. Higher utilization of primary and specialty care for women was associated with lower self-report-ed health status, less education, and lower socioeconomic status in our previous study.²⁹