Are executive function and neuroanatomy in ADHD modulated by bilingualism?

It has been proposed that bilinguals have better executive function (EF) arising from the constant selection of one language while inhibiting the other, and gray matter has been found to differ in bilinguals in regions linked to EF (frontal-parietal and subcortical structures). Attention Deficit Hyperactivity Disorder (ADHD) is associated with poorer EF and neuroanatomical differences underlying EF. Given the EF advantage in bilinguals, we investigated whether a bilingual experience affects EF performance and brain structure differentially in those with ADHD. Using the Adolescent Brain and Cognitive Development Study, we compared early Spanish-English bilinguals and English-speaking monolinguals with and without ADHD. ANOVAs for the Flanker, Working Memory, and Card Sort Tasks revealed no main effects of Language Experience (Bilingual versus Monolingual), a main effect of Diagnostic Group for Card Sort (ADHD worse than Controls), and no interaction effects on performance for any task. ANOVAs for gray matter volume (GMV) revealed a main effect of Language Experience in many regions, a main effect of Diagnostic Group in some regions, but no interactions. GMV in left thalamus was affected by both ADHD and bilingualism, but the effect of ADHD was not significantly diminished or enhanced by the dual-language experience. For cortical thickness, there was a main effect of Language Experience in several regions, no main effect of Diagnostic Group, and no interactions. Taken together, bilingualism has some impact on EF performance, a strong impact on neuroanatomy, but there was no disproportionate impact by bilingualism on the differences caused by ADHD for any measure. Research HighlightsExecutive function and brain structure differ in ADHD and in bilinguals, prompting the need to investigate interactive effects. Bilingualism did not disproportionately affect performance differences in ADHD for executive function, nor for gray matter volume or for cortical thickness differences in ADHD. Gray matter volume was less in ADHD than non-ADHD, as well as greater in bilinguals than monolinguals in the left thalamus, but without interaction effect. These independent effects indicate that the brain basis of ADHD is not impacted by a dual-language experience.