Bipolar disorder — sometimes called manic-depressive disorder — causes mood swings that range from of the lows of depression to the highs of mania. When you become depressed, you may feel sad or hopeless and lose interest or pleasure in most activities. When your mood shifts in the other direction, you may feel euphoric and full of energy. Mood shifts may only occur only a few times a year, or as often as several times a day. In some cases, bipolar disorder causes symptoms of depression and mania at the same time.