It is important to note that average IQ score is significantly lower in the ADHD group; therefore one may argue that IQ differences might account for the findings. As poorer performance in IQ test may be interpreted as an inherent characteristic of ADHD (and of other neurodevelopmental disorders), covarying IQ when studying ADHD might be inappropriate as one would be controlling for a component of the disorder (Dennis et al., 2009). However, we recognize that this is not a universal view and, as such, decided to examine the effect of IQ differences on our findings by repeating the comparison analysis after matching for IQ scores. The table with the demographics for the new group is shown in the Supplementary Material, Table S.2. Supplementary Figure S.1 displays the results and shows that lower IQ scores in the ADHD group does not account for our findings.
