American physician who first showed that bipolar disorder (also called "manic-depression") is caused by an imbalance between two types of neurotransmitters in the brain. Made in 1972, this discovery was one of the first to show that some mental illness has an organic basis—that it is due to a physical problem in the brain and is analogous to diabetes and other similar diseases. This, in turn, has helped remove some of the stigma associated with mental illness.