Major depressive episode

A major depressive episode is characterized by the presence of a severely depressed mood that persists for at least two weeks. Episodes may be isolated or recurrent and are categorized as mild (few symptoms in excess of minimum criteria), moderate, or severe (marked impact on social or occupational functioning). An episode with psychotic features—commonly referred to as psychotic depression—is automatically rated as severe. If the patient has had an episode of mania or markedly elevated mood, a diagnosis of bipolar disorder is made instead.Depression without mania is sometimes referred to as unipolar because the mood remains at one emotional state or "pole".

DSM-IV-TR excludes cases where the symptoms are a result of bereavement, although it is possible for normal bereavement to evolve into a depressive episode if the mood persists and the characteristic features of a major depressive episode develop. The criteria have been criticized because they do not take into account any other aspects of the personal and social context in which depression can occur. In addition, some studies have found little empirical support for the DSM-IV cut-off criteria, indicating they are a diagnostic convention imposed on a continuum of depressive symptoms of varying severity and duration:excluded are a range of related diagnoses, including dysthymia which involves a chronic but milder mood disturbance, Recurrent brief depression which involves briefer depressive episodes, minor depressive disorder which involves only some of the symptoms of major depression, and adjustment disorder with depressed mood which involves low mood resulting from a psychological response to an identifiable event or stressor.