In the book, she challenges the notion that a positive attitude can increase chances of survival. "There's a widespread idea – it sounds so familiar that you let it go right by you – that your immune system will be boosted if you are thinking positively," she said. "Well, there's not a whole lot to support that. And, more to the point, it's not clear that the immune system has anything to do with recovery from cancer or with whether you get it in the first place.