A neuroanatomical basis for co-occurring low attention and low reading ability.

Attention deficit hyperactivity disorder (ADHD) and dyslexia are two common disorders that can have devastating impacts on child development and occur together more often than one would expect by chance. Identifying imaging markers characteristic of a combined ADHD and dyslexia phenotype could improve our ability to diagnose these entities early and inform our understanding of the underlying disease processes. In this study, we set out to determine whether there are unique cortical, white matter, or subcortical characteristics in adolescents with combined low attention (LA) and low reading ability (LR), which we utilized as behavioral surrogate markers of ADHD and dyslexia. We conducted a retrospective, cross-sectional analysis using imaging, demographic, genetic, and neuropsychiatric data from 8779 individuals in the Adolescent Behavioral Cognitive Development study. We modeled cortical area, subcortical volume, and white matter integrity (fractional anisotropy) across brain regions and white matter tracts as functions of LA and LR. Cortical area was reduced in both LA and LR separately, with overlapping reductions in orbitofrontal cortex that persist in vertex-wise maps after adjustment for total cortical area. Global white matter integrity uniquely differed in individuals with combined LA/LR. These findings are most supportive of a shared underlying susceptibility for ADHD and dyslexia.