J. RAYMOND DePAULO Jr., M.D., is a professor of psychiatry and Director of the Affective Disorders Clinic at the Johns Hopkins University School of Medicine. Internationally known as a clinician, teacher, and research expert on depression and bipolar disorder, Dr. DePaulo has won many awards for research and teaching, and he has been selected as one of the "Best Doctors in America" in each of the three editions of the book with that title. LESLIE ALAN HORVITZ is a freelance writer based in New York. His most recent book, Eureka!: Scientific Breakthroughs that Changed the World, is also published by Wiley.