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...

Instead of asking why certain people suffer from mental illness, Nesse asks why natural selection has left us all with fragile minds. Drawing on revealing stories from his own clinical practice and insights from evolutionary biology, Nesse shows how negative emotions are useful in certain situations, yet can become overwhelming. Anxiety protects us from harm in the face of danger, but false alarms are inevitable. Low moods prevent us from wasting...