The effect of initial antidepressant type on treatment adherence in outpatients with new onset depression.

Background: Continuous use of antidepressants can relieve depressive symptoms and prevent recurrence in people with depression; however, many studies have reported low drug compliance rates. This study aimed to investigate the relationship between the type of initial antidepressants and treatment adherence in outpatients with new onset depression.
Methods: This was a retrospective cohort study using National Health Insurance claim data for services provided in 2012. We examined data from 142,336 individuals aged 18 years or older, who were continuously enrolled in treatment after a new episode of depression, and had initiated antidepressant treatment. A new diagnosis of depression, is defined as a first reported diagnosis of depression in the preceding five years. Adherence was operationally defined as the antidepressant being dispensed to the patient at least 80% of the time during the first three- and six-month treatment periods. To investigate the relationship between the initial type of antidepressants and treatment adherence, we estimated adjusted odds ratios and 95% confidence intervals using logistic regression analysis, adjusting for socio-demographic and health care utilization characteristics.
Results: A statistically significant association was found between initial antidepressant type and adherence in the first three- and six-month treatment periods for employed and self-employed patients newly diagnosed with major depression. In addition, patients with starting prescriptions for tricyclic antidepressants had significantly lower adherence compared to selective serotonin reuptake inhibitors.
Limitations: This study used national insurance data; therefore, only variables on the claim form were available, and psychological and environmental factors were not considered.
Conclusions: This was the first study to demonstrate the relationship between initial antidepressant type and treatment adherence among Korean outpatients with new onset depression.
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