Abstract

Background: Low adherence to medications has been previously associated with an increased burden of medical costs. The aim of the present study was to investigate whether antidepressant (AD) adherence is associated with increased use of healthcare resources.
Methods: The frequency, appropriateness and cost of diagnostic tests in patients with depressive/anxiety disorders in relation to AD adherence were evaluated using Arianna database, covering a population of 168,397 inhabitants. New AD users with depressive/anxiety disorders, >1 year run-in period and 3 years of follow-up after the first AD prescription were identified. As comparator group, up to two non-users of ADs from the same population were matched to AD users on age (±2 years) and sex. AD treatment adherence was categorized as low (<20%), medium (20-80%) and high (≥80%) at the end of the first year of therapy by calculating the proportion of days covered. During the next two years of follow-up, the comorbidity- adjusted frequency, appropriateness and cost of diagnostic tests for AD users and non-users were evaluated, stratifying by class (Selective Serotonin Reuptake Inhibitors-SSRI and other ADs) and adherence for AD users.
Results: Overall, 3,225 (1.9%) AD users (mean age: 56.7±16.4) and 6,205 non-users were included. Low adherent SSRI users (77.0%) received a higher number of diagnostic tests than highly adherent SSRI users (73.0%). Diagnostic tests, in particular CT scans, cardiological visits and ECG tests, were more likely to be inappropriate in SSRI users with low rather than high adherence. A greater cost for diagnostic tests was observed in low adherent AD users (mean: €185.8) than in those highly adherent (mean: €171.9) and non-users (mean: €167.3).
Conclusion: Greater adherence to AD treatment may modestly reduce the use of some potentially inappropriate diagnostic tests although it does not appear to be a major determinant.