ABSTRACT
Unipolar depressive disorder or major depressive disorder (MDD) is characterized by depressive symptoms without any history of a manic, mixed, or hypomanic episode. MDD is a severe mood disorder, associated with significant morbidity and mortality that affects individuals of all ages and races. The mean age of onset of MDD is approximately 30 years. The disorder has a median life prevalence of 4.5-18%. It occurs in about 5-10% of the adult population, with women being at a higher risk than men (the ratio is approximately 2 : 1). Female gender, a previous episode of major depression, and a first-degree family history of depression are the most consistently described risk factors for a depressive episode. Untreated MDD has decreasing episode cycles with increasing episode number. Although the prognosis of MDD is generally considered quite favorable (e.g. most patients return to normal functioning with pharmacologic treatment), up to 20-30% of patients suffer chronically from at least some of their symptoms.1
