Modeling Shared and Specific Variances of Irritability, Inattention, and Hyperactivity Yields Novel Insights Into White Matter Perturbations.

OBJECTIVE: Irritability, inattention, and hyperactivity, which are common presentations of childhood psychopathology, have been associated with perturbed white matter microstructure. However, similar tracts have been implicated across these phenotypes; such non-specificity could be rooted in their high co-occurrence. To address this problem, we use a bifactor approach parsing unique and shared components of irritability, inattention, and hyperactivity, which we then relate to white matter microstructure.

METHOD: We developed a bifactor model based on the Conners Comprehensive Behavioral Rating Scale in a sample of youth with no psychiatric diagnosis or a primary diagnosis of attention-deficit/hyperactivity disorder or disruptive mood dysregulation disorder (n = 521). We applied the model to an independent yet sociodemographically and clinically comparable sample (n = 152), in which we tested associations between latent variables and fractional anisotropy (FA).

RESULTS: The bifactor model fit well (comparative fit index = 0.99; root mean square error of approximation = 0.07). The shared factor was positively associated with an independent measure of impulsivity (ρS  = 0.88, pFDR  < .001) and negatively related to whole-brain FA (r = -0.20), as well as FA of the corticospinal tract (all pFWE  < .05). FA increased with age and deviation from this curve, indicating that altered white matter maturation was associated with the hyperactivity-specific factor (r = -0.16, pFWE  < .05). Inattention-specific and irritability-specific factors were not linked to FA.

CONCLUSION: Perturbed white matter microstructure may represent a shared neurobiological mechanism of irritability, inattention, and hyperactivity related to heightened impulsivity. Furthermore, hyperactivity might be uniquely associated with a delay in white matter maturation.