There is some indication that the incidence of bipolar disorder may be increasing, but more research is needed to confirm this. Bipolar disorder affects both sexes equally, but women are about three times more likely to experience rapid cycling. One center reported that bipolar disorder in children may be more common than previously believed. It may be underdiagnosed in this age group because it can be often confused with attention-deficit hyperactivity disorder. In addition, symptoms of bipolar disorder may be different in children than in adults When the onset of the condition occurs at these younger ages, the initial episodes may be primarily depressive.
Irritability is common.
Young patients tend to experience frequent episodes and increasing social problems, even if their family situations are positive. Manic phases usually begin in adolescence or young adulthood, with average age of onset being 18. Bipolar disorder that develops in elderly people is less likely to be associated with a family history of the disorder and more likely to accompany medical and neurologic problems than earlier-onset bipolar disorder. Family History Bipolar disorder often occurs within families. Studies of identical twins raised apart found that about two-thirds of the pairs shared the disorder when one twin had it.