Antidepressant Medication Adherence: A Study of Primary Care Patients

Background: Nonadherence to antidepressant medication significantly contributes to the undertreatment of depression in primary care populations. The purpose of this study was to survey primary care patients’ adherence to antidepressant medication to better understand factors associated with nonadherence.

Method: Participants with a history of being prescribed an antidepressant for at least 4 weeks were recruited from a primary care research network. Subjects completed a demographic survey, the Patient Health Questionnaire (PHQ), the Beck Depression Inventory-II (BDI-II), the Medical Outcomes Study (MOS) 36-Item Short-Form Health Survey, the Interpersonal Support Evaluation List, the Stages of Change Scale, the Medication Adherence Scale, and the MOS measure of adherence. Differences between adherent and nonadherent patients were compared using χ² for discrete variables, independent t tests for continuous variables, and Mann-Whitney U tests for rank-ordered data. Data were collected from April 1, 2001 to April 1, 2004.

Results: Approximately 80% (N = 148) of individuals approached for this study agreed to participate. The overall sample was primarily white and female. The PHQ diagnoses at study entry were dysthymic disorder (8.8%, n = 13), major depressive disorder (31.8%, n = 47), “double depression” (both dysthymic disorder and major depressive disorder, 29.7%, n = 44), and no depression (16.2%, n = 24.) The mean BDI-II score for the total sample was 19.9. Nonadherent patients reported being more careless about taking their medications, were more worried about side effects, were less satisfied with their physicians, were under the age of 40 years, and were more likely to have asked for a specific antidepressant. Nonadherent patients also indicated being at lower stages of change.

Conclusions: Individually tailoring education to patient preference and stage of change is recommended to promote adherence.