the control group may have IQ=100 and the ADHD group have 103.
It is safe to see that ADHD is not related to IQ. But, ADHD is more correlated to learning disability (LD). An example: an ADHD child's IQ is 124, but he scores are the 5th but last in hte class.This fact has been the decisive factor for the diagnosis.
I will keep you posted.