Impact of adherence to antidepressants on healthcare outcomes and costs among patients with type 2 diabetes and comorbid major depressive disorder.

OBJECTIVE

To evaluate the association between adherence to antidepressants and an effect on clinical outcomes and healthcare costs in patients with major depressive disorder (MDD) and comorbid type 2 diabetes (T2D).

METHODS

This retrospective study used MarketScan claims data from January 2012 to March 2014. Study entry was the first claim for an antidepressant and a diagnosis code for MDD and T2D in the prior 6 months. Adherence and persistence with antidepressant therapy in the first 180 days were defined as medication possession ratio (MPR) ≥ 80% and length of therapy (LOT), with no treatment gap of >15 days, respectively. T2D control (HbA1c <7%), oral diabetes medication adherence, and healthcare costs were measured in the 12 month post-index period. The impact of antidepressant adherence and persistence on outcomes was assessed using multivariable analyses.

RESULTS

Among the 1361 patients included, the mean age was 59 years and 55% were women. About one-third of the patients were adherent (35.9%, mean MPR = 40%), persistent (32.0%, average LOT = 100 days), and adherent/persistent (31.2%) on antidepressants. Being adherent, persistent, or adherent/persistent to antidepressants was associated with a two-fold improvement in adherence to oral diabetes medications. Of those with HbA1c data (n = 121), adherence or adherence/persistence to antidepressants was associated with patients being five times more likely to have T2D control (odds ratio [OR]: 4.95; 95% confidence interval [CI]: 1.39, 17.59, p = .0134). Comparison between antidepressant-persistent and non-persistent patients was not significant. Mean difference in adjusted all-cause annual costs showed lower costs among antidepressant-adherent and adherent/persistent patients (adherent: -$350, 95% CI: -$462, -$247; adherent/persistent: -$1165; 95% CI: -$1280, -$1060).

CONCLUSIONS

Patients with better antidepressant adherence and adherence/persistence demonstrated better HbA1c control, with lower all-cause total and medical costs. Adherence, persistence, or adherence/persistence to antidepressants was associated with improved adherence to oral diabetes medications.