1. Female or male aged between 18 and 65 years Inpatients and outpatients diagnosed with an episode of major depression relating to RDD (ICD-10, Version 2010) during the period from January 1, 2012 till September 30, 2013 3. Initially treated with antidepressant monotherapy, using a flexible dosage regimen if required, for at least 2 weeks 4. Initial treatment changed because of a suboptimal response at physician's discretion, which is clearly documented in the patient's medical chart.