There is considerable epidemiological and neuropsychological evidence that ADHD is best considered dimensionally, lying at the extreme of a continuous distribution of symptoms and underlying cognitive impairments. We thus asked if cortical brain development in typically developing children with symptoms of hyperactivity and impulsivity resembles that found in the syndrome. Specifically, we found that a slower rate of cortical thinning during late childhood and adolescence, which we previously found in ADHD, is also linked with severity of symptoms of hyperactivity and impulsivity in typically developing children, providing neurobiological evidence for the dimensionality of the disorder.
