Adherence to Antidepressant Medication

Abstract: Non-adherence to medication is a major obstacle in the treatment of depression. The objectives of the present study were to explore the effect of two interventions aiming to increase antidepressant treatment adherence, and to examine long-term consequences and costs of depression in adherent and non-adherent primary care patients. A randomised controlled design was used to assess the respective effects of a written educational adherence enhancing programme and therapeutic drug monitoring in patients with major depression treated with sertraline for 24 weeks. All patients were prospectively followed during two years. Treatment adherence was found in 41% of the 1031 included patients. None of the interventions resulted in a significant increase in adherence rate. However, significantly more patients in the group receiving the written educational material had responded at week 24 as compared to patients in the control group. The overall remission rate after two years was 68%. In total, 34% of the responders experienced at least one relapse. Response and remission rates at week 24, year 1 and year 2 were significantly higher in adherent as compared to non-adherent patients. No relationship between adherence and relapse rate was seen. The mean total cost per patient during two years was KSEK 363 whereof indirect costs represented 87%. No significant differences in costs between intervention groups or between adherent and non-adherent patients could be demonstrated. However, the mean cost per patient was 39% lower for treatment responders as compared to non-responders. Non-adherence was predicted by age below 35 or above 64 years, no concomitant medications, personality disorder, sensation seeking personality traits and substance abuse. The results indicate a strong positive relationship between treatment adherence and clinical outcome. In addition, the study shows that depression is a costly disease and that certain patient characteristics predict non-adherence.