Normal variation in behavioral adjustment relates to regional differences in cortical thickness in children

Neuroanatomical correlates of developmental psychopathology such as attention deficit hyperactivity and conduct disorder have been identified. The majority of studies point to lesser gray matter in psychopathology, often involving prefrontal cortices. The goal of this study was to test whether similar neural correlates exist for behavioral variance in healthy children and adolescents. A large sample (n = 106) aged 8-19 years underwent MR scanning and their parents completed the Strength and Difficulties Questionnaire. The relationships between cortical thickness and conduct problems and hyperactivity/inattention scale scores were investigated throughout the cerebrum. No associations were found between normal variance in hyperactivity/inattention and cortical thickness. Normal variance in conduct problems was associated with thinner left hemisphere prefrontal and supramarginal cortices. Relationships between conduct problems and cortical thickness interacted with age, with the greatest differences in cortical thickness seen in the younger children. These interactions were observed in the anterior cingulate, orbitofrontal, middle and superior frontal, as well as lateral and medial temporal cortices. In conclusion, the results indicate neurobiological continuity between symptoms of conduct problems within the normal range, and conduct disorder. Relationships of thinner cortices and conduct problems were primarily seen in younger children, and appeared to decrease with age, indicative of different maturational trajectories in the groups. The long-term consequences are unknown, and the results point to a need for longitudinal studies of developmental trajectories of neuroanatomical foundations of behavioral adjustment.