Among these, the condition of "rapid cycling" has been receiving substantial interest, with the recognition that 10% to 15% of patients with diagnosed bipolar I or bipolar II disorder have cycle lengths of such short duration that they suffer 4 or more cycles per year (vs the more typical temporal pattern of 4 episodes in 10 years).[4-6] Patient characteristics that are associated with rapid cycling include female gender and hypothyroidism that is independent of its greater overall prevalence in females and is without evidence of familial association.