Age-Specific ADHD and Internalizing/Externalizing Comorbidity in Children with Neurofibromatosis Type 1: A Multi-Site Study

Objective: The current study tested (1) how ADHD symptoms and internalizing or externalizing problems covaried across ages 3–18 in children with neurofibromatosis type 1 (NF1), and (2) whether demographic and NF1-specific factors moderated the associations. Method: We analyzed integrated cross-sectional data of 685 observations from 455 children and adolescents with NF1 (Mage = 9.79 years, SD = 3.88; 43% female) across six institutions in the United States and Australia. ADHD symptoms (inattention and hyperactivity/impulsivity) and internalizing/externalizing problems were assessed via parent-report measures. Time-varying effect modeling was employed to examine the age-specific associations between ADHD symptoms and internalizing/externalizing problems. Moderation analyses tested effects of sex, parental education, and NF1 inheritance mode (familial vs. sporadic). Results: Inattention and hyperactivity/impulsivity symptoms were associated with greater internalizing and externalizing problems across ages 3–17. Inattention links were similar across ages, while the hyperactivity/impulsivity-externalizing link was stronger in early childhood than during adolescence. NF1 inheritance mode significantly moderated the inattention-externalizing link, with stronger associations observed among children with familial NF1. Other moderators were nonsignificant. Conclusions: ADHD symptoms are robustly linked to internalizing and externalizing problems from childhood to middle adolescence in children with NF1, with familial NF1 emerging as a potentially elevated risk factor. Future longitudinal and experimental research is needed to inform integrated intervention approaches, especially for those with familial NF1.