Pain can be a disease too, not a symptom alone

We think of pain as a symptom, but there are cases where the nervous system develops feedback loops and pain becomes a terrifying disease in itself. Starting with the story of a girl whose sprained wrist turned into a nightmare,  in a TedTalk Dr Elliot Krane talks about the complex mystery of chronic pain, and reviews the facts we're just learning about how it works and how to treat it.