Neurostructural Substrates of Hierarchical Dimensions of Internalizing Symptoms in Youth

Internalizing symptoms are common in childhood and linked to meaningful differences in brain structure, yet their organization and neurobiological correlates during this developmental period remain poorly understood. An increasing number of studies conceptualize internalizing psychopathology as dimensional, transdiagnostic, and hierarchical, yet the factor structure of these symptoms in youth remains to be clearly defined. Additionally, the neurostructural underpinnings of internalizing factors warrants further investigation in younger samples. Using a large sample (N = 11,868) of 9- to 10-year-old children from the Adolescent Brain Cognitive Development^SM (ABCD Study), we examined the factor structure of internalizing symptoms and identified associated neurostructural correlates, focusing on regional gray matter volume, cortical thickness, and cortical surface area. Higher-order modeling was used, in which the correlations among first-order factors for distress, cognitive, fear, and somatic symptoms were accounted for by a higher-order general internalizing factor. After controlling for age, sex, income, parental education, and site/MRI scanner, we found that general internalizing, distress, and cognitive symptoms were associated with smaller gray matter volume and cortical surface area across most regions. Fear symptoms showed a more localized pattern of smaller surface area in the parietal, temporal, and insular cortices. Cortical thickness and somatic symptoms showed less consistent associations. These findings contribute to the growing literature on dimensional models of internalizing psychopathology in youth by linking higher- and lower-order internalizing symptom factors to distinct patterns of neurostructural variation. Our results support the utility of hierarchical dimensional approaches for elucidating the neural substrates of internalizing symptoms during middle childhood.