Attrition can pose significant barriers to treatment success of depression; its contributing factors and impacts on treatment outcome need further clarification. Current study aimed to describe patterns of treatment attrition, to examine associated demographic and clinical determinants and to test whether and how attrition affects outcome of depression in a national cohort of adults treated for depression.

All adult patients prescribed with antidepressants for depression (n=216,557) in 2003 were identified from the National Health Insurance Research Database in Taiwan. Based on individuals’ clinical visit and antidepressant prescription, three attrition types, i.e., non-attrition, returning attrition and non-returning attrition, and their demographic/disease characteristics were identified. The relationships between attrition type and remission outcome over an 18-month follow-up period were further explored.

Factors pertaining to disease characteristics (severity of depression, comorbidities, painful physical symptoms and past treatment history) and clinical practice (physician specialty and choice of antidepressants) were associated with attrition and remission outcome at 18-month follow-up. Patients remaining in treatment within the first three months were associated with higher odds of having sustained remission (OR=1.21; 99% CI: 1.16, 1.27) and lower odds of having relapses/recurrences (OR=0.20; 99% CI: 0.19, 0.21) over the 18-month period, compared to those returning attriters.

Early attrition has significant negative impacts on antidepressant treatment outcome; it hence needs to be minimized through shared decision-making, exchange of treatment preferences and proper patient-physician communication. Based on current understanding, further efforts to reduce early attrition are highly warranted.