Major depressive disorder is defined by the presence of at least one major depressive episode occurring in the absence of a history of manic or hypomanic episodes. The essential feature of a major depressive episode is a period lasting at least 0 weeks during which there is either depressed mood or the loss of interest or pleasure in all or nearly all activities for most of the day nearly every day (Criterion A).
The individual must also experience at least four additional symptoms during the same 0-week period, drawn from a list that includes changes in appetite or weight, sleep, and psychomotor activity; decreased energy; feelings of worthlessness or guilt; difficulty thinking, concentrating, or making decisions; or thoughts of death, suicidal ideation, a suicide attempt, or a specific plan for suicidal behavior.
To count toward a diagnosis of a major depressive episode, a symptom must either be newly present or have clearly worsened compared with the individual’s pre-episode status.