Background: Depression is a common comorbidity for patients with chronic medical conditions. Although the costs of treating chronic medical illness in combination with depression are believed to be significantly higher than the costs of treating each condition independently, few studies have formally modeled the cost consequences of mental health comorbidity.
Purpose: To estimate the relative magnitude of the independent and synergistic contributions to health care costs from depression diagnosis and other chronic physical health conditions.
Methods: Cross-sectional, observational study using all individuals >18 years of age in the national Blue Cross Blue Shield (BCBS) Axis claims database (N = 43,872,144) from calendar year 2018. General linear models with and without interaction terms were used to assess the relative magnitude of independent and synergistic contributions to total annual health care costs of depression alone and in combination with coronary heart disease, chronic kidney disease, chronic obstructive pulmonary disease, diabetes (both types 1 and 2), hypertension, and arthritis.
Results: The incremental annual cost associated with having a diagnosis of depression was $2,951 compared to $1,986-$6,251 for the other chronic physical conditions. The interaction between depression and chronic conditions accounted for less than one-hundredth of the amount of variation in costs explained by the main effects of depression and each chronic physical condition.
Conclusions: The independent increase in total annual health care costs associated with a depression diagnosis was comparable to that of many common physical chronic conditions. This finding underscores the importance of health care service and payment models that acknowledge depression as an equal contributor to overall health care costs. The combination of depression and another chronic condition did not synergistically increase total annual health care costs beyond the increases in costs associated with each condition independently. This finding has implications for simplifying risk adjustment models.
Keywords: Chronic disease; Depression; Health care costs.
It is widely believed that depression, when combined with other chronic physical conditions, systematically inflates health care costs. For example, it is assumed that the costs of caring for a patient with both depression and heart disease are higher than the costs of caring for each condition independently. Using a database that included 43 million commercially insured people in the United States, we found that the costs of care for patients with depression were comparable to the costs for patients with other chronic medical conditions. This result supports the need for mental health parity and for trained mental health care providers in medical settings. We then considered the costs of caring for people with depression with or with or without one of seven common chronic physical condition. Contrary to expectation, the combination of depression and any of the diagnoses appeared to have largely independent relationships with health care costs. The results contradict the suggestion that depression and chronic condition diagnoses act synergistically to inflate health care expenditures.
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