Bipolar II Disorder

The form of the disease where people do not develop severe mania but experience milder episodes of hypomania that change with depression. Bipolar II disorder can be thought of as a less severe form of bipolar I disorder. It is defined as at least one major depressive episode accompanied by at least one hypomanic episode. One key criterion that distinguishes this disorder from bipolar I is that the person has never experienced a manic or mixed episode. Bipolar II disorder may be further categorized as hypomanic or depressed, depending on whether the patient is currently, or most recently, in a hypomanic or depressed state. It is important to note that patients with bipolar II disorder are often misdiagnosed as having unipolar depression. If a manic or mixed episode develops over the course of bipolar II disorder, the diagnosis is changed to bipolar I disorder. Over a 5-year period, an estimated 5% to 15% of individuals with bipolar II disorder will develop a manic episode.