Bipolar Disorders Bipolar disorder comes in many forms. This is a common source of confusion, since most books on the subject are about bipolar-I, which is the least common type of bipolar. Bipolar-I affects 1 in 100 people; the other forms are 2-4 times more common than this. The word bipolar means “two poles”: mania and depression. This word captures bipolar-I very well, but as you’ll see the other forms of bipolar would be more accurately captured by the word “cyclical moods.” In these other forms, people cycle in and out of depression and other mood states. Click below to read more about each form: Bipolar I Bipolar II Cyclothymia Bipolar Spectrum After reading these, the next section is Mind & Brain. —Updated 8/5/11 by Chris Aiken, MD