Bipolar II disorder is similar to bipolar I disorder except that mania is absent in bipolar II disorder and hypomania (a milder form of elevated mood than mania) is the essential diagnostic finding.

Epidemiology
Lifetime prevalence is about 0.5%. Bipolar II disorder may be more common in women.

Etiology
Current evidence implicates the same factors as for bipolar I.

Clinical Manifestations
History and Mental Status Examination
Bipolar II disorder is characterized by the occurrence of hypomania and episodes of major depression in an individua1 who has never met criteria for mania or a mixed state Hypomania is determined by the same symptom complex as mania but the symptoms are less severe, cause less impairment, and usually do not require hospitalization. Bipolar II disorder is cyclic (see Fig. 2-2B for course of untreated bipolar II). Suicide occurs in 10% to 15%.

Differential Diagnosis
Same as for bipolar I.

Management
Treatment is the same as for bipolar I disorder, although hypomanic episodes typically do not require as aggressive a treatment regimen as mania.
Care must be taken in prescribing antidepressants for depression or dysthymia because of their role in prompting more severe or frequent hypomanic episodes.