Patterns of persistence with pharmacological treatment among patients with current depressive episode and their impact on long-term outcome: a naturalistic study with 5-year follow-up

BACKGROUND: The aim of the study was to describe and compare the patterns of medication persistence among patients with unipolar depression (UD) or bipolar depression in a 5-year follow-up, and explore their impact on long-term outcome. PATIENTS AND METHODS: A total of 333 eligible patients with current major depressive episode were observed and followed up from the first index prescription for 5 years. Lack of persistence or treatment interruption was defined as a gap of at least 2 consecutive months without taking any medication. Time to lack of persistence in the first (TLP1) and the second (TLP2) episode of treatment, number of visits before the first treatment interruption (NV) and number of treatment interruptions (NTI) were measured. RESULTS: During the 5-year follow-up, nearly 50% of patients experienced at least two times of treatment interruption. Pattern of medication persistence did not significantly differ between UD and bipolar disorder (BD) patients. TLP1 was positively associated with TLP2. Shorter TLP1 predicted a higher possibility of subsequent visits because of recurrence or relapse and more NTI meant a lower likelihood of achieving full remission in the fifth year for both UD and BD patients. For UD patients, shorter TLP1 or less NV predicted a lower chance of achieving remission, while for BD patients, shorter TLP1 meant an earlier subsequent visit and more NTI predicted a lower possibility of achieving remission. CONCLUSION: Pattern of medication persistence was similar but its impact on the long-term outcome was quite different between UD and BD.