Bipolar II Disorder
This type of bipolar disorder is characterized by one or more major depressive episodes with at least one hypomanic episode in which hospitalization is not required. By definition, no full manic episodes are present in Bipolar II.
The lifetime prevalence of Bipolar II Disorder internationally is 0.3% and is 0.8% in U.S. samples.
Cyclothymia is characterized by at least a two-year period of numerous hypomanic or depressive episodes, but none have been severe enough for a diagnosis of either full mania or major depressive disorder. Individuals with Cyclothymia do not remain symptom-free for more than two months at a time, by definition.
The diagnosis of cyclothymia cannot be made casually. Two full years of documented bipolar symptoms of the proper intensity must have been observed prior to diagnosis. If the mood swings can be better accounted for by the criteria of schizoaffective disorder, then that diagnosis occurs. If mood swings are considered to be a part of a larger schizophrenic disorder, then Cyclothymia becomes an associated feature of a psychotic disorder. If one or more mood episodes reach a severe stage where criteria for mania or major depressive disorder are met, then a diagnosis of Bipolar I or II is appropriate. Additionally, medical conditions such as hypothyroidism must be eliminated as the cause of bipolar symptoms before this diagnosis may be made. Substance-related disorders and sleep disorders may be associated with Cyclothymia.
Cyclothymic Disorder symptoms often begin adolescence or early adulthood. The condition typically has a slow, gradual, and progressive onset and a chronic course once established. There is a 15-50% chance that individuals with cyclothymia will go on to develop bipolar I or II disorders. In community samples, cyclothymic disorder symptoms are apparently equally common in men and in women. As with all bipolar disorders, a general medical condition or substance abuse problem must be excluded in order for this diagnosis to stand.
Lifetime prevalence of Cyclothymia is 0.4% to 1% in community samples. [DSM]