Bipolar disorder, formerly known as manic-depressive illness or manic depression, is a mental illness that causes unusual changes in mood, energy, level of activity, concentration, and capacity for daily tasks.Bipolar disorder comes in three varieties. Changes in mood, energy, and activity levels are evident in all three. These moods range from periods of behavior that are extremely "up," ecstatic, irritable, or energized (manic episodes) to periods...