Dimensional Brain-Behavior Relationships in Children with Attention-Deficit/Hyperactivity Disorder

Abstract

Background Emerging neuroscientific and genetic findings emphasize the dimensional rather than the categorical aspects of psychiatric disorders. However, the integration of dimensional approaches within the current categorical diagnostic framework remains unclear. Here, we used resting state fMRI (R-fMRI) to examine whether dimensional measures of psychiatric symptomatology capture brain-behavior relationships unaccounted for by categorical diagnoses. Additionally, we examined whether dimensional brain-behavior relationships are modified by the presence of a categorically defined illness, Attention-Deficit/Hyperactivity Disorder (ADHD). Methods R-fMRI scans were collected from 37 typically developing children (aged 10.2±2; 21 females) and 37 children meeting DSM-IV-TR criteria for ADHD (9.7±2; 11 females). Parent-rated Child Behavior Checklist Externalizing and Internalizing scores served as dimensional measures in our analyses of default network (DN) resting state functional connectivity (RSFC). Results Regardless of diagnosis, we observed several significant relationships between DN RSFC and both Internalizing and Externalizing scores. Increased Internalizing scores were associated with stronger positive intra-DN RSFC, while increased Externalizing scores were associated with reduced negative RSFC between DN and “task-positive” regions such as dorsal anterior cingulate cortex. Several of these brain-behavior relationships differed depending on the categorical presence of ADHD. Conclusions Our findings suggest that while categorical diagnostic boundaries provide an inadequate basis for understanding the pathophysiology of psychiatric disorders, psychiatric illness cannot be viewed simply as an extreme of typical neural or behavioral function. Efforts to understand the neural underpinnings of psychiatric illness should incorporate both categorical and dimensional clinical assessments.

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