Symptoms of a Major Depressive Episode usually develop over days to weeks. A prodromal period that may include anxiety symptoms and mild depressive symptoms may last for weeks to months before the onset of a full Major Depressive Episode. The duration of a Major Depressive Episode is also variable. An untreated episode typically lasts 4 months or longer, regardless of age at onset. In a majority of cases, there is complete remission of symptoms, and functioning returns to the premorbid level. In a significant proportion of cases (perhaps 20%-30%), some depressive symptoms insufficient to meet full criteria for a Major Depressive Episode may persist for months to years and may be associated with some disability or distress (in which case the specifier In Partial Remission may be noted; page 412).
Partial remission following a Major Depressive Episode appears to be predictive of a similar pattern after subsequent episodes. In some individuals (5%-10%), the full criteria for a Major Depressive Episode continue to be met for 2 or more years (in which case the specifier Chronic may be noted).