Thank you dubstepped. Any information you have gathered is welcome and greatly appreciated.
The hospital psychologist told us it's fairly common as a side effect of childhood leukemia chemo treatment. Roughly 20% of ADHD is other than genetic. Think chemo brain/fog amplified. It was likely the steroid they had him on for 3-1/2 years. It's listed as one of the side effects of prednisone. His diagnosis came back as moderate ADHD.