Caudate nucleus volume asymmetry predicts attention-deficit hyperactivity disorder (ADHD) symptomatology in children.

Clinical diagnosis of attention-deficit hyperactivity disorder (ADHD) is based on evaluation of behavioral functioning in three domains: inattentiveness, hyperactivity, and impulsivity. Caudate and frontal lobe function figures prominently in several neuroanatomic models of attentional functioning. Studies comparing children with and without ADHD have found differences in the size and symmetry of the caudate nuclei. Using multiple regression, we tested the hypothesis that caudate volume symmetry (log left minus log right caudate volume) measured from serial sagittal magnetic resonance images in a sample of nonreferred children (12 girls/15 boys, 7.0 to 16.6 years, 81 to 129 IQ) would predict the cumulative severity of parent-reported ADHD diagnostic behaviors beyond variance predicted by age, sex, and level of internalizing problems as measured by the Child Behavior Checklist. No child had been previously diagnosed with ADHD, although one child was found to meet diagnostic criteria based on the rating scale used for the study. The degree of caudate asymmetry significantly predicted cumulative severity ratings of inattentive behaviors (P = .015), uniquely accounting for 17.1% of the variance in inattention symptomatology over demographic variables and internalizing problems, which collectively predicted 28.9% of the variance. Caudate asymmetry uniquely accounted for only 4.3% of the variance in cumulative severity ratings of hyperactive/impulsive symptomatology over demographic variables and internalizing problems that collectively predicted 21.2% of the variance. A greater degree of right to left caudate volume asymmetry predicted subclinical inattentive behaviors in a sample of nonreferred children. This finding is congruent with neuroanatomic models of attention emphasizing lateralized alteration in prefrontal/striatal systems. The results support the view that clinical ADHD is the extreme of a behavioral continuum that extends into the normal population.