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Impact of antidepressant drug adherence on comorbid medication use and resource utilization.

Katon W, Cantrell CR, Sokol MC, Chiao E, Gdovin JM

Division of Health Services and Psychiatric Epidemiology, Department of Psychiatry, University of Washington Medical School, Seattle, USA.

BACKGROUND: Patients with depression are often nonadherent to therapy for depression and chronic comorbid conditions. METHODS: To determine whether improved antidepressant medication adherence is associated with an increased likelihood of chronic comorbid disease medication adherence and reduced medical costs, we conducted a retrospective study of patients initiating antidepressant drug therapy with evidence of dyslipidemia, coronary artery disease (CAD), or both; diabetes mellitus (DM); or CAD/dyslipidemia and DM identified from a claims database. Measures included antidepressant medication adherence, measured by medication possession ratio during 180 days without a 15-day gap before 90 days of therapy; comorbid medication adherence, measured by medication possession ratio during 1 year; and the association between improved antidepressant drug adherence and disease-specific and total medical costs. RESULTS: Of 8040 patients meeting the study criteria, those adherent to antidepressant medication were more likely to be adherent to comorbid therapy vs those nonadherent to antidepressant drug therapy (CAD/dyslipidemia: odds ratio [OR], 2.13; DM: OR, 1.82; and CAD/dyslipidemia/DM: OR, 1.45; P<.001 for all). Patients adherent to antidepressant drug therapy also had significantly lower disease-specific charges vs nonadherent patients (17% lower in CAD/dyslipidemia, P = .02; 8% lower in DM, P = .39; and 14% lower in CAD/dyslipidemia/DM, P = .38). These patients also incurred lower total medical charges (6.4% lower in CAD/dyslipidemia, P = .048; 11.8% lower in DM, P = .04; and 19.8% lower in CAD/dyslipidemia/DM, P = .03). CONCLUSIONS: Antidepressant drug adherence was associated with increased comorbid disease medication adherence and reduced total medical costs for CAD/dyslipidemia, DM, and CAD/dyslipidemia/DM. Future studies should investigate the relationship between increased adherence and costs beyond 1 year.

Published 29 November 2005 in Arch Intern Med, 165(21): 2497-503.
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