The essential feature of Bipolar I Disorder is a clinical course that is characterized by the occurrence of one or more Manic Episodes or Mixed Episodes. Often individuals have also had one or more Major Depressive Episodes. Episodes of Substance-Induced Mood Disorder (due to the direct effects of a medication, other somatic treatments for depression, a drug of abuse, or toxin exposure) or of Mood Disorder Due to a General Medical Condition do not count toward a diagnosis of Bipolar I Disorder. In addition, the episodes are not better accounted for by Schizoaffective Disorder and are not superimposed on Schizophrenia, Schizophreniform Disorder, Delusional Disorder, or Psychotic Disorder Not Otherwise Specified. Bipolar I Disorder is subclassified in the fourth digit of the code according to whether the individual is experiencing a first episode (i.e., Single Manic Episode) or whether the disorder is recurrent.
Recurrence is indicated by either a shift in the polarity of the episode or an interval between episodes of at least 2 months without manic symptoms. A shift in polarity is defined as a clinical course in which a Major Depressive Episode evolves into a Manic Episode or a Mixed Episode or in which a Manic Episode or a Mixed Episode evolves into a Major Depressive Episode. In contrast, a Hypomanic Episode that evolves into a Manic Episode or a Mixed Episode, or a Manic Episode that evolves into a Mixed Episode (or vice versa), is considered to be only a single episode. For recurrent Bipolar I Disorders, the nature of the current (or most recent) episode can be specified (Most Recent Episode Hypomanic, Most Recent Episode Manic, Most Recent Episode Mixed, Most Recent Episode Depressed, Most Recent Episode Unspecified).