Bipolar disorder is a mental disorder that is characterized by constantly changing moods between depression and mania. The mood swings are significant, and the experiences of the highs of mania and the lows of depression are usually extreme. The new mood can last anywhere from a few days to a few weeks, or even months (see the bipolar cycling section below). The mood swings are usually experienced intensely by a person with this condition.A manic episode is characterized by extreme happiness, hyperactivity, little need for sleep, and racing thoughts, which may lead to rapid speech. A depressive episode is characterized by extreme sadness, a lack of energy or interest in things, an inability to enjoy normally pleasurable activities, and feelings of helplessness and hopelessness. On average, someone with bipolar disorder may have up to three years of normal mood between episodes of mania or depression.Bipolar disorder is recurrent, meaning that more than 90 percent of the individuals who have a single manic episode will go on to experience future episodes. Roughly 70 percent of manic episodes in bipolar disorder occur immediately before or after a depressive episode. Treatment seeks to reduce the feelings of mania and depression associated with the disorder and restore balance to the person's mood.Those with bipolar disorder often describe their experience as being on an emotional roller coaster.