traveler, the reason a lot of medical studies are vague is trying to sort out cause and effect, for example if a study showed that educated Northern people were more likely to get lung cancer, this could be done to heredity, their jobs, lifestyle, or indeed a magic cancer causing organism only found north of the Watford Gap. Logic tells us that it is lifestyle, but it takes a lot of studies with a lot of people to confirm that statisically. Tricky one really and why the first thing you should look at in a "new report" is the number of people in the study. Anything less than several hundered is, in my view, merely speculation, and when dealing with something with a low incidence, you need to be into the thousands before I'd trust them.
There is a figure in most medical reports that's called the confidence number (IIRC) from what I remember 1 is definate and 0 means they were wrong