Neuroanatomical Correlates of Heterotypic Comorbidity in Externalizing Male Adolescents

Children and adolescents with externalizing behavior disorders including attention-deficit=hyperactivity disorder (ADHD) and conduct disorder (CD) often present with symptoms of comorbid internalizing psychopathology. However, few studies have examined central nervous system correlates of such comorbidity. We evaluated inter-actions between externalizing and internalizing symptoms in predicting mesolimbic, septo-hippocampal, and anterior cingulate volumes among 12- to 16-year-old boys with either ADHD, ADHD and CD, or no psychiatric condition (n 35). These regions were chosen given established links to trait impulsivity, trait anxiety, and behavior regulation, respectively. Collapsed across groups, Externalizing Internalizing symptom inter-actions accounted for individual differences in gray matter densities in each region. Externalizing youth with comorbid internalizing symptoms showed smaller reductions in gray matter than individuals with externalizing psychopathology alone. These results suggest that internalizing symptoms are associated with less severe structural com-promises in brain regions subserving motivation and behavior regulation among externalizing boys