In the last 10 years researchers have been looking at them.
The researchers looked at data from more than 125,000 people.
No matter how the researchers looked at it, the results came out the same.
But it seems researchers were looking in the wrong place.
That may be, but researchers are still looking for an answer.
We both knew that I'm just the sort of person the researchers are looking for.
And medical researchers, looking for data, say they are not always certain themselves about how to decide.
The researchers also looked at side effects that developed in each group.
As a result, researchers are looking again for possible causes.
But negative results may simply mean that researchers did not look in the right places.