Interactive Associations of Race and Comorbidity in Medication Treatment and Outcomes of Medicaid Enrolled Patients with Major Depressive Disorder.

Background Comorbid anxiety disorders commonly occur in patients with Major Depressive Disorder (MDD). Treatment disparities of depression between African Americans and Caucasians still exist. Few studies have investigated the association of race and comorbid anxiety disorders with medication use-related outcomes in Medicaid enrollees with MDD. Objectives The objectives of this study was to examine the association of race, comorbid anxiety disorders, and the interaction between race and comorbid anxiety disorders with medication adherence, medication persistence, and health resource utilization in Medicaid enrollees with MDD. Methods MarketScan® Multi-State Medicaid Database were used in this retrospective cohort study. Adult Medicaid enrollees between 18 and 64 years of age with MDD but without bipolar disorders who received an antidepressant between January 1, 2004 and December 31, 2006 were identified. Patients with a 24-month continuous enrollment and without dual eligibility of Medicaid and Medicare were included. A Cox-propositional hazard regression was used to examine the risk of non-persistent antidepressant use. Multivariate logistic regressions were used to model the probability of adherence and health care utilization. Multivariate negative binominal regression analyses were used to assess the rate of change of health care utilization. Multivariate linear regressions with log-transformed costs were used to assess the health care costs. Results Approximately 25% of 3,083 patients had comorbid anxiety disorders. After controlling for covariates, comorbid anxiety disorders were significantly associated with higher adherence and more frequent mental health-related health care utilization. African Americans were less likely than Caucasians to adhere to antidepressants and had higher risk of non-persistence. Additionally, African-American patients had fewer mental health-related office visits but were more likely to be hospitalized and have ER visits. The interaction effect (being African American and having comorbid anxiety disorders) reduced the individual association with health care utilization. Conclusion African-American patients were less likely than Caucasian patients to be adherent to or persistently use antidepressants. Comorbid anxiety disorders were associated with higher health resource utilization. Health policy makers and health care providers need to decrease the disease burden of comorbid anxiety disorders and reduce health disparities between Caucasians and African Americans among Medicaid enrollees with MDD.Ph.D.Social & Administrative SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/77712/1/chunghwu_1.pd