Clinical and economic impact of non-adherence to antidepressants in major depressive disorder: a systematic review

BACKGROUND: Medication non-adherence is one of the major challenges in treating patients with depression. This systematic review aims to determine the clinical and economic outcomes of non-adherence in depression.

METHODS: A systematic search was performed across the following databases: PubMed, EMBASE, DARE, CINAHL, PsycINFO, Cochrane Central Register of Controlled Trials, and Cochrane Database of Systematic Reviews; from database inception to March 31, 2015. Studies must report on the association between adherence and outcomes, and English full texts needed to be available. The quality of each study was assessed using the Newcastle-Ottawa scale.

RESULTS: A total of 11 articles were included, with eight reporting on clinical outcomes, two reporting on economic outcomes, and one reporting on both. The majority of studies were retrospective cohort studies. The mean quality of all included studies was 7, with a range from 3 to 9. Results clearly indicate that patients who were non-adherent were more likely to experience increased risks of relapse and/or recurrence, emergency department visits, and hospitalization rates; increased severity of depression, and a decrease in response and remission rates. The worsening of clinical outcomes in patients who were non-adherent subsequently translated to an increase in healthcare utilization and charges.

LIMITATIONS: No standardized adherence measurement tools were used, and few studies looked at the economic impact of non-adherence in depression.

CONCLUSION: There is a strong association between non-adherence to antidepressants and a worsening of patients' clinical and economic outcomes. Cost-effective interventions should be directed to this group of patients to improve medication adherence.