Bipolar disorder, also known as manic depressive disorder, 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 or four times a year, with respites between. For some people, depression and mania cycle continuously. There are also people who experience mixed episodes, in which 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 it occurs twice, it is usually followed by other episodes). Generally, the depressive phase lasts longer than the manic phase, and 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 much 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. Up to 20% 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.
The illness is sometimes linked to seasonal affective disorder, with depression occurring in late fall or winter, giving way to remission in the spring, and progressing to mania or hypomania in the summer.