Well it's a fact that some people chain smoke their whole life and never get lung (or any other type of) cancer. While others who never have smoked do.
Which means that because a person who smokes gets lung cancer, it's not necessarily because he smokes. He might have got it anyway.
And if everyone is told that smoking causes cancer, and they believe it, it is obvious that smokers statistically will have a higher rate of lung cancer than non-smokers, if these principles here are true.
So the statistics that seem to indicate that smokers have a higher rate of lung cancers actually supports both the claim that smoking causes cancer, as well as the claim that it's your belief that smoking causes cancer that causes it.
This is the tricky thing with this belief thing - there is always an element of belief involved in whatever you do, and if beliefs can do what is claimed here, it's very difficult to do objektive and neutral research.
Also check out the "nocebo effect", which is quite well documented. It's quite interesting what beliefs actually can do to your body:
"Japanese researchers tested 57 high school boys for their sensitivity to allergens. The boys filled out questionnaires about past experiences with plants, including lacquer trees, which can cause itchy rashes much as poison oak and poison ivy do. Boys who reported having severe reactions to the poisonous trees were blindfolded. Researchers brushed one arm with leaves from a lacquer tree but told the boys they were chestnut tree leaves. The scientists stroked the other arm with chestnut tree leaves but said the foliage came from a lacquer tree. Within minutes the arm the boys believed to have been exposed to the poisonous tree began to react, turning red and developing a bumpy, itchy rash. In most cases the arm that had contact with the actual poison did not react."
http://www.skepdic.com/nocebo.html
http://www.washingtonpost.com/ac2/wp-dyn?pagename=article&node=&contentId=A2709-2002Apr29¬Found=true
