This is almost all research though. (Medical) doctors aren't in the habit of doing longitudinal studies on procedures they don't do because they don't believe i

This is almost all research though. (Medical) doctors aren't in the habit of doing longitudinal studies on procedures they don't do because they don't believe in them. (I mean, for one thing, where would they get the data!) But that's why you have peer review, further studies from different authors perhaps on competing methods that point out some flaws in your approach, etc.