The essential feature of Major Depressive Disorder is a clinical course that is characterized by one or more Major Depressive Episodes (see page 349) without a history of Manic, Mixed, or Hypomanic Episodes (Criteria A and C). Episodes of Substance-Induced Mood Disorder (due to the direct physiological effects of a drug of abuse, a medication, or toxin exposure) or of Mood Disorder Due to a General Medical Condition do not count toward a diagnosis of Major Depressive Disorder. In addition, the episodes must not be better accounted for by Schizoaffective Disorder and are not superimposed on Schizophrenia, Schizophreniform Disorder, Delusional Disorder, or Psychotic Disorder Not Otherwise Specified (Criterion B).
The fourth digit in the diagnostic code for Major Depressive Disorder indicates whether it is a Single Episode (used only for first episodes) or Recurrent. It is sometimes difficult to distinguish between a single episode with waxing and waning symptoms and two separate episodes. For purposes of this manual, an episode is considered to have ended when the full criteria for the Major Depressive Episode have not been met for at least 2 consecutive months. During this 2-month period, there is either complete resolution of symptoms or the presence of depressive symptoms that no longer meet the full criteria for a Major Depressive Episode (In Partial Remission).
The fifth digit in the diagnostic code for Major Depressive Disorder indicates the current state of the disturbance. If the criteria for a Major Depressive Episode are met, the severity of the episode is noted as Mild, Moderate, Severe Without Psychotic Features, or Severe With Psychotic Features. If the criteria for a Major Depressive Episode are not currently met, the fifth digit is used to indicate whether the disorder is In Partial Remission or In Full Remission.
If Manic, Mixed, or Hypomanic Episodes develop in the course of Major Depressive Disorder, the diagnosis is changed to a Bipolar Disorder. However, if manic or hypomanic symptoms occur as a direct effect of antidepressant treatment, use of other medications, substance use, or toxin exposure, the diagnosis of Major Depressive Disorder remains appropriate and an additional diagnosis of Substance-Induced Mood Disorder, With Manic Features (or With Mixed Features), should be noted. Similarly, if manic or hypomanic symptoms occur as a direct effect of a general medical condition, the diagnosis of Major Depressive Disorder remains appropriate and an additional diagnosis of Mood Disorder Due to a General Medical Condition, With Manic Features (or With Mixed Features), should be noted.