The impact of the type of insurance plan on adherence and persistence with antidepressants: a matched cohort study

To compare adherence to, and persistence with, antidepressants (AD) in Quebec patients who are covered by private and public drug insurance.

A matched cohort study was conducted using prescription claims databases: reMed, a medication data registry for Quebec residents covered by private drug insurance, and Régie de l'assurance maladie du Québec database for Quebec residents with public drug insurance. Patients were aged 18 to 64 years and filled at least 1 prescription for an AD in monotherapy between December 2007 and September 2009 (194 privately and 2055 publicly insured patients). Adherence over 1 year was estimated using the proportion of prescribed days covered (PPDC). The difference in mean PPDC between patients with private and public drug insurance was estimated with linear regression. Persistence was compared between the groups with a Cox regression model.

The PPDC was 86.4% (95% CI 83.3% to 89.5%) in privately insured and 82.2% (95% CI 78.5% to 85.9%) in publicly insured patients and the adjusted mean difference was 5.1% (95% CI 1.6% to 8.6%). Persistence was 51.0% in the private group and 19.7% in the public group at 1 year (P < 0.001); the adjusted hazard ratio was 0.49 (95% CI 0.30 to 0.79).

Better adherence and persistence were observed in privately insured patients. Adherence difference may be due to lower copayment among privately insured patients.