A Cohort Study of Adherence to Antidepressants in Primary Care

OBJECTIVE: Clinical guidelines recommend that antidepressant treatment should be continued for a minimum of 6 months following response in depression and anxiety disorders. However, adherence to antidepressants is low. This prospective cohort study investigated the influence of patients' antidepressant concerns, treatment preferences, and illness perceptions on adherence to antidepressants over a 6-month period. METHOD: A cohort of 178 patients aged 18 to 74 years and newly issued with a prescription for antidepressants to treat any condition was followed up prospectively at 5 primary care practices in Southeast England. Adherence was measured through self-report and prescription refill data. Patient perceptions were quantified using validated outcome measures, the Beliefs about Medicine Questionnaire and the Illness Perception Questionnaire, at 4 timepoints. Patient treatment preferences were recorded using a specially designed questionnaire. Data collection took place between September 2000 and May 2002. RESULTS: Of 147 participants (83%) who completed the study, 19% persisted with antidepressants in accordance with guideline recommendations throughout the 6-month period. Specific concern about antidepressant side effects (OR = 3.30, 95% CI = 2.20 to 4.97) and general worry about taking antidepressants (OR = 1.65, 95% CI = 1.13 to 2.40) were independent predictors of antidepressant nonuse. Preference for different treatment/uncertainty about preferred treatment was also a strong predictor (OR = 3.82, 95% CI = 1.35 to 10.77). However, illness perceptions were not associated with adherence. CONCLUSIONS: Concerns about antidepressants and a mismatch between patients' preferred and prescribed treatment act as significant barriers to sustained adherence. This study highlights the central role of the patient-physician partnership in exploring antidepressant concerns, working with treatment preferences, and providing supportive continued management. The findings may inform the development of interventions within primary care programs to enhance commitment to treatment for common mental disorders.