The term bipolar disorder refers to a group of brain diseases that cause moods to fluctuate widely and uncontrollably. It can cause you to move from depression to mania, from spirit-crushing and potentially life-threatening lows to dangerous highs. These extreme fluctuations have a negative impact on a person's energy level, thoughts, behavior, and ability to function. Although not curable, bipolar disorder can be controlled with treatment. It is difficult to determine precisely how many people have this disorder, but the National Institute of Mental Health estimates that approximately 5.7 million adults are dealing with it in the U.S. This means two or three out of every 100 adults in the U.S. has some form of bipolar disorder. Half of them are over twenty-five years of age when they develop the disease. Worldwide, more than 250 million people may have bipolar disorder.