Introduction
Bipolar disorder is often a cyclic illness where people periodically exhibit elevated (manic) and depressive episodes. Most people will experience a number of episodes, averaging 0.4 to 0.7 a year with each lasting three to six months, although some will experience only a single mood episode. Late adolescence and early adulthood are peak years for the onset of the illness. These are critical periods in a young adult's social and vocational development, and they can be severely disrupted by disease onset.
Rapid cycling, defined as having four or more episodes per year, is found in a significant fraction of patients with bipolar disorder. It has been associated with greater disability or a worse prognosis, due to the confusing changeability and difficulty in establishing a stable state. Rapid cycling can be induced or made worse by antidepressants, unless there is adjunctive treatment with a mood stabilizer.
The definition of rapid cycling most frequently cited in the literature is that of Dunner and Fieve: at least four major depressive, manic, hypomanic or mixed episodes are required to have occurred during a 12-month period. There are references that describe very rapid (ultra-rapid) or extremely rapid (ultra-ultra or ultradian) cycling. One definition of ultra-ultra rapid cycling is defining distinct shifts in mood within a 24–48-hour period.