Time to lack of persistence with pharmacological treatment among patients with current depressive episodes: a natural study with 1-year follow-up

INTRODUCTION: Medication nonadherence remains a big challenge for depressive patients. This study aims to assess and compare the medication persistence between unipolar depression (UD) and bipolar depression (BD). METHODS: A total of 146 UD and 187 BD patients were recruited at their first index prescription. Time to lack of persistence with pharmacological treatment (defined as a gap of at least 60 days without taking any medication) was calculated, and clinical characteristics were collected. Final diagnosis was made at the end of 1-year follow-up. RESULTS: A total of 101 (69.2%) UD and 126 (67.4%) BD patients discontinued the treatment, with a median duration of 36 days and 27 days, respectively. No significant difference was found between UD and BD in terms of time to lack of persistence with pharmacological treatment. The highest discontinuation rate (>40%) occurred in the first 3 months for both groups of patients. For UD patients, those with a higher risk of suicide (odds ratio [OR] =0.696, P=0.035) or comorbidity of any anxiety disorder (OR =0.159, P<0.001) were less likely to prematurely drop out (drop out within the first 3 months), while those with onset in the summer (OR =4.702, P=0.049) or autumn (OR =7.690, P=0.012) were more likely to prematurely drop out than those with onset in the spring (OR =0.159, P<0.001). For BD patients, being female (OR =2.250, P=0.012) and having a history of spontaneous remission or switch to hypomania (OR =2.470, P=0.004) were risk factors for premature drop out, while hospitalization (OR =0.304, P=0.023) and misdiagnosis as UD (OR =0.283, P<0.001) at the first index prescription were protective factors. LIMITATION: Conservative definition of nonadherence, low representativeness of sample. CONCLUSION: Treatment discontinuation was frequently seen in patients with UD or BD, especially in the first 3 months of treatment. In spite of the similar pattern of medication persistence, UD and BD differ from each other in predictors of premature drop out.