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The Halo Effect of Adherence to Anti-Depressants

Background & Introduction

The impact of depression on medication adherence has been well documented in literature, with past studies showing that depressed individuals are far less likely to be adherent to their medication regimens than their non-depressed counterparts1. Researchers have demonstrated this relationship across a number of chronic disease areas, including those that top the charts in total annual healthcare spend, such as diabetes and renal disease2.

To further examine this relationship, AllazoHealth analyzed historical adherence data across a population of ~45,000 Medicare Advantage Part D patients. The objective was to better understand the relationship between adherence to anti-depressants and adherence to the three major medication classes impacting STAR ratings: oral anti-diabetics, RAS antagonists, and statins.

Analyses & Results

AllazoHealth first sought to understand how current adherence to anti-depressant medications might influence the likelihood of future adherence to oral anti-diabetics, RAS antagonists, and statins (Table 1). For this analysis, adherence was defined as achieving a Proportion of Days Covered (PDC) of >=80%. Overall, we found a positive correlation between adherence to anti-depressants and the likelihood of adherence to the other medication classes. The largest impact was observed for statins, with adherence to anti-depressants increasing the likelihood of future adherence to statins by 33%.

Table 1. How Anti-Depressant Adherence Impacts Likelihood of Adherence to other Medications

AllazoHealth also examined how increases and decreases in anti-depressant adherence affected adherence rates for oral anti-diabetics, RAS antagonists, and statins. We found that patients with an increase in PDC for their anti-depressants also saw “spillover effect” in their adherence to oral anti-diabetics, RAS antagonists, and statins (Figure 1). The reverse, while not graphically shown here, was also true — patients with a decrease in their PDC for anti-depressants saw a decrease in their adherence to other medications.

Figure 1. January and April PDC for Patients As PDC for Anti-Depressants Rises


AllazoHealth’s findings further support the correlation frequently observed between adherence to anti-depressants and adherence to other medication classes. While causality was not the main focus of this study, the results do tell a compelling narrative that treating and managing adherence to anti-depressants can lead to benefits in other disease areas.

To find learn more about this study or to understand how AllazoHealth can enhance your intervention programs, please visit or email us directly at



  1. Dimatteo RM, Lepper HD, Croghan TW. Depression is a risk factor for noncompliance with medical treatment: meta-analysis of the effects of anxiety and depression on patient adherence. Arch Intern Med 2000;160:2101 –7.
  2. Wing R, Plelan S, Tate D. The role of adherence in mediating the relationship between depression and health outcomes. Journal of Psychosomatic Research 2002;52:877-81=