Bipolar disorder (BD, previously known as manic depression) is a mood disorders where the person experiences states or episodes of depression and/or mania, hypomania, and/or mixed states. The difference between bipolar disorder and unipolar disorder (also called major depression), is that bipolar disorder involves "energized" or "activated" mood states in addition to depressed mood states. The duration and intensity of these mood states varies widely among people with the illness. The fluctuating component of this illness is called "cycling" from one mood state to another at varying rates. For most individuals with bipolar disorder, the condition is disabling and the individual has tremendous difficulty functioning. The etiology of bipolar disorder is thought to include a complex interplay between epigenetic and genetic vulnerability and environmental events (stressful life events, major achievements, difficult relationships with family and/or significant others, drug use and other physical and social phenomena).
