Background: Treatment utilization/costs and work performance for persons with major depressive disorder (MDD) by severity of illness is not well documented.
Methods: Using National Comorbidity Survey-Replication (2001-2002) data, US workforce respondents (n=4,465) were classified by clinical severity (not clinically depressed, mild, moderate, severe) using a standard self-rating scale [Quick Inventory of Depressive Symptomatology Self-Report (QIDS-SR)]. Outcomes included 12-month prevalence of medical services/medications use/costs and workplace performance. Treatment costs (employer's perspective) were estimated by weighing utilization measures by unit costs obtained for similar services used by MDD patients in claims data. Descriptive analysis across three severity groups generated chi(2) results.
Results: Using a sample of 539 US workforce respondents with MDD, 13.8% were classified mild, 38.5% moderate, and 47.7% severe cases. Mental health services usage, including antidepressants, increased significantly with severity, with average treatment costs substantially higher for severe than for mild cases both regarding mental health services ($697 vs. $388, chi(2)=4.4, P=.019) and antidepressants ($256 vs. $88, chi(2)=9.0, P=.001). Prevalence rates of unemployment/disability increased significantly (chi(2)=11.7, P=.003) with MDD severity (15.7, 23.3, and 31.3% for mild, moderate, and severe cases). Severely and moderately depressed workers missed more work than nondepressed workers; the monthly salary-equivalent lost performance of $199 (severely depressed) and $188 (moderately depressed) was significantly higher than for nondepressed workers (chi(2)=10.3, P<.001). Projected to the US workforce, monthly depression-related worker productivity losses had human capital costs of nearly $2 billion.
Conclusions: MDD severity is significantly associated with increased treatment usage/costs, treatment adequacy, unemployment, and disability and with reduced work performance.