My pediatrician said to me on our first visit that it takes 20 years to change clinical practice. That parents are changing the treatment of autistic and sensory children simply because they demand it. And that if we waited for clinicians to do it, we'd be waiting too long because children grow up too fast.
In that same vein I just read this article on gluten sensitivity: http://online.wsj.com/article/SB10001424052748704893604576200393522456636.html.
In two separate places the woman who runs the gluten intolerance group of north america says that patients have been told that it's in their head or they are crazy if they don't have celiac but still react to gluten. Their symptoms simply written off as psychiatric. It also says, "Peter Green, director of the Celiac Disease Center says that research into gluten sensitivity today is roughly where celiac disease was 30 years ago."