Bipolar disorder (BD), previously referred to as manic depressive illness, is a chronic multiphasic illness characterized by periods of mania and depression. There are two major types of BD. Bipolar Type I Disorder (BD-I) is characterized by the occurrence of more severe mania, typically interspersed with episodes of moderate to severe major depressive episodes. In Bipolar Type II (BD-II), the manic phase is not severe enough to interfere with functioning, but the moderate to severe major depressive episodes are equally disabling. Importantly, both BPI and BPII are diseases that are different than what is referred to as "depression", and different treatments are often needed. Both BD-I and BD-II are serious psychiatric illnesses that affect up to 5.5% of the population and can result in severe impairment of occupational and interpersonal function, especially if untreated.