With my daughter, I often wonder which came first: the anxiety from the cognitive issues or the cognitive issues from the anxiety (her anxiety is severe). Or a bit of both. There are so many variables with our kids, it's hard to tell.
by the way, fishingdad - there are threads in the archive re: ADHD and executive function that you might find insightful. I'm not implying this is the case with your child, but it can't hurt to to take a read.