Bipolar disorder, also known as manic depressive illness, is a serious, double-edged mental illness. In contrast to the sustained bleakness of major depression (technically called unipolar disorder when episodes only involve major depression and no manic or hypomanic periods), bipolar disorder is characterized by cyclical periods of high energy and elation and then low energy and despair. The pattern of the mood alternations varies widely among those with the disorder. In some people, years of normal functioning can separate manic and depressive episodes. In others, the episodes cycle frequently, three, four, or more times a year, with respites in between. For some people, depression and mania cycle continuously. There are also people who experience episodes with mixed features, in which symptoms of mania and depression occur together or alternate rapidly within a brief period of time. And for a rare few, an episode of bipolar disorder may occur only once in a lifetime. If an episode occurs twice, it is usually followed by others. Generally, the depressive phase lasts longer than the manic phase. It also tends to be more frequent. The cycle can be erratic.
Bipolar disorder is known to affect about 2.6% of U.S. adults in any given year, although its frequency may be somewhat higher because cases go untreated or misdiagnosed. Men and women are equally susceptible. Much evidence suggests that the illness has at least a partial genetic basis, but its origins are still uncertain. The symptoms are thought to result from abnormal functioning of brain circuits that regulate mood, thinking, and behavior and are beyond voluntary control. The disorder is not only life-disrupting but can also be dangerous. As many as 10% to 15% of people with bipolar disorder commit suicide, usually when they are in the midst of a severe depression and may feel particularly hopeless about the future.
Fortunately, great strides have recently been made in treating this illness. In most cases, the symptoms can be controlled effectively by medication and other therapies.
The disorder occurs in two main forms, known as bipolar I and bipolar II. They may have separate genetic origins. In bipolar I, both phases of the illness are apt to be very pronounced. In bipolar II, mania is often mild (it is termed hypomania), and the depression can be either mild or severe. Bipolar II is more difficult to diagnose and is often mistaken for unipolar or major depressive disorder. It has fewer and shorter periods of remission than bipolar I, tends to be more common in women, and is somewhat less responsive to treatment. It may be the more common form of bipolar disorder.