ATP2C2 and attention deficit-hyperactivity disorder: Nonetheless, the association detected in our samples shows a strong correlation to nonword-repetition ability which has repeatedly been shown to be a strong indicator of language impairment.9,10 Furthermore, in ADHD samples, performance on the nonword-repetition task is correlated with linguistic ability rather than the presence of hyperactivity.33,36 Thus, we conclude that variants in ATP2C2 might account for shared aspects of the linguistic deficit in SLI and ADHD.