Bipolar disorder is also known as manic-depressive illness and is a brain disorder that causes unusual shifts in mood, energy, activity levels, and the ability to carry out day-to-day tasks. These moods range from periods of extremely “up,” elated, and energized behavior (known as manic episodes) to very sad, “down,” or hopeless periods (known as depressive episodes). Sometimes a mood episode includes symptoms of both manic and depressive symptoms and is termed as an episode with mixed features. People experiencing an episode with mixed features may feel very sad, empty, or hopeless, while at the same time feeling extremely energized.