Are you me??? Lol. Im 38 and I got diagnosed this spring too. I had a neurologist put me on the XR. I recently went to a psychiatrist and he said he was surprised I started on the xr. He switched me to instant release and wants me to experiment with doses. I actually did ask him the exact question you pose. He basically said its so complex noone really knows. Those whi claim they know its more wishful thinking than anything. He said more things that went over my head. The main taleaway for me was, dont get caught up on that part. I really havent noticed much of a difference FWIW.