Objective: The aim of this study was to assess the relative contributions of diabetes complications, depression and comorbid medical disorders to health service costs in adults with diabetes.
Methods: A total of 4398 adult health plan members with diabetes completed a mailed survey. Depression was assessed using the nine-item PHQ. Health service costs, diabetes complications, glycohemoglobin levels and comorbid medical conditions were assessed using computerized health plan records.
Results: Total health service costs were approximately 70% higher for individuals with major depression than for those without any depressive disorder (5361 US dollars over 6 months vs. 3120 US dollars, P<.001); this difference was consistent across all categories of health service costs. Diabetes complications were the strongest predictor of total costs (6845 US dollars for those with three or more complications vs. 1719 US dollars for those with none), but depression remained strongly associated with increased costs at all levels of diabetes severity.
Conclusions: Among people with diabetes, depression is associated with 50-75% increases in health service costs. This proportional difference is similar to that in general population samples, but the absolute dollar difference is much greater. The effect of depression on health service use is undoubtedly complex and not limited to unexplained physical symptoms among the worried well.