In the 1850s, "Drapetomania" was the medical term for a disease found among black slaves in the United States. The main symptom was a strange desire to run away from their masters. In earlier centuries gout was understood as a metabolic disease of the affluent, so much so that it became a badge of uppercrust honor-and a medical excuse to avoid hard work. Today, is there such a thing as mental illness, or is mental illness just a myth? Is Alzheimer's...