Evaluating the Association of Initial Benzodiazepine Use and Antidepressant Adherence among Adults with Anxiety Disorders

Objective: The purpose of this study was to evaluate whether co-prescription of benzodiazepine when initiating antidepressant treatment is associated with better antidepressant adherence than initiating treatment with antidepressants alone among patients with anxiety disorders. Methods: We conducted a retrospective observational cohort study using MarketScan Commercial Claims and Encounters database (Thomson Reuters). We identified patients aged 18-64 with anxiety disorders (including generalized anxiety disorder, panic disorder, social anxiety disorder, obsessive-compulsive disorder, and post-traumatic stress disorder), who were newly receiving a selective serotonin reuptake inhibitor or serotonin-norepinephrine reuptake inhibitor between July 1, 2005 and June 30, 2007. We compared those who were co-prescribed a benzodiazepine at antidepressant initiation with those who begun on an antidepressant alone. The outcome measure was antidepressant adherence rate measured as the proportion of days covered (PDC) on antidepressant treatment. Patients with PDC ≥80% were considered adherent. We used propensity score matching to balance measurable confounders. Logistic regression models were used to measure adherence. Results: Our study included 6949 patients who were co-prescribed benzodiazepines and antidepressants, and 6949 patients receiving antidepressants alone after matching for propensity scores. Before adjusting covariates, patients in the co-prescribed benzodiazepine group had lower adherence to antidepressants (PDC: 0.52 vs. 0.60, p < 0.01). After adjusting the covariates, we found that patients in the co-prescribed benzodiazepine group were less likely to adhere to antidepressant treatment (odds ratio = 0.70; 95% confidence interval = 0.65-0.75) when compared with patients using antidepressants alone. Conclusion: This is the largest analysis with an observational study design to date. Our study results showed that patients with anxiety who are co-prescribed benzodiazepines when initiating treatment with antidepressants are less likely to adhere to antidepressants than those who begin treatment with antidepressants alone. Further research should clarify whether co-prescribing benzodiazepines with antidepressant initiators is a preferred clinical strategy for those with anxiety disorders.