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

Background: Patients with depression are often non-adherent 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 I 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 non-adherent 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 non-adherent patients (17% lower in CAD/dyslipidemia, P=.02; 8% lower in DM, P=39; and 14% lower in CAD/dyslipiderma/ 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.