Schizophrenia and bipolar disorder affect 3% to 4% of the world's population, or about 222 million adults worldwide. In the United States, bipolar disorder affects about 5.7 million adult Americans 18 and older. Bipolar disorder, or manic depression, is a serious brain disorder that causes extreme shifts in mood, energy and functioning. People with the disorder experience episodes of mania and depression that can last from days to months. These symptoms usually begin in late adolescence, but can begin in early childhood or as late as a person's 40s or 50s. There is a strong genetic component related to bipolar disorder.