Medication non-compliance is common in the treatment of depression, particularly in Asia.

1) To describe the frequency and factors associated with medication non-compliance. 2) To study the influence of non-compliance on treatment outcomes.

Nine hundred and nine in- and out-patients from Asia presenting with a new or first episode of major depressive disorder were enrolled in a 3-month prospective observational study. Clinical severity and quality of life were assessed, using Hamilton Depression Scale (HAMD-17), Clinical Global Impression Severity (CGI-S), and EuroQoL measures (EQ-5D and EQ-VAS). Medication compliance was also assessed by the investigator and patient. Linear and logistic multiple regression models were used to analyze the consequences of non-compliance.

The proportion of non-compliant patients as assessed by the investigator was 16%. Sociodemographic factors and clinical severity were not associated with compliance at baseline. Regression models showed that medication non-compliance was associated with worse depression severity (difference in HAMD-17 -3.98; 95% CI -5.10, -2.87) and overall clinical severity (CGI-S difference -0.46; 95%CI -0.68, -0.24) at three months. Medication non-compliance was also associated with lower quality of life at three months (EQ-VAS difference -7.47; 95%CI -11.13, - 3.82) and EQ-5D score difference -0.08; 95%CI -0.1, -0.04)). Compliant patients had higher odds of response (odds ratio (OR) 3.18; 95% CI 1.98, 5.10) and remission (OR 3.94; 95% CI 2.42, 6.43) compared with non-compliant patients.

Patients non-compliant with medication had worse 3-month outcomes in terms of depression severity, quality of life, and response and remission rates, compared with compliant patients.