What causes mental illness? Traditionally, we've blamed bad parenting, stress, trauma, genetics, and brain-chemistry imbalances. But in recent years, a new theory has quietly achieved critical mass. In her astonishing new book, author Harriet Washington reveals that many instances of schizophrenia, obsessive-compulsive disorder, Alzheimer's, Tourette's, bipolar disorder, and anorexia are likely caused by bacteria, parasites, or viruses. That's right--you...