Also note the existence of some already known underlying limiting factors on people's reading speed. E.g. there's a connection between working memory capacity deficits and "processing speed" in ADHDers.
"Abnormalities in working memory and response selection may play an important role in deficits in reading fluency in ADHD, potentially more than posteriorally mediated problems with orienting of attention or perceiving the stimulus."
(Supposedly) the same for other disorders potentially harmful to working memory - e.g. anxiety disorders.