Sad. Incredibly happy. Invincible. Suicidal. Those are the mood swings that occur when people have bipolar disorder. People with depression do not experience the highs of those with bipolar disorder. Instead they feel very sad for at least a week. Between 2 million and 3 million Americans suffer from bipolar disorder, which usually appears just after the teen years, but can start much earlier. More than 9 million people in the United States have depression...