Peer victimization and the association with hippocampal development and working memory in children with and without ADHD 

Background: Children with ADHD are at risk of experiencing peer victimization, which is associated with delayed brain development and cognitive difficulties. We aimed to evaluate the relationship between problem behaviours, peer victimization, hippocampal morphology, and working memory in children with and without ADHD. Methods 218 typically developing participants (50.5% male) and 232 participants diagnosed with ADHD (77.6% male) were recruited. The ADHD group was subdivided into inattentive (ADHD-I) or combined (ADHD-C) type. The Child Behaviour Checklist measured problem behaviours and peer victimization. Hippocampal subfield volumes were obtained using Magnetic Resonance Imaging and the Wechsler Intelligence Scale for Children-fifth edition measured working memory (WM). Results The ADHD-C group displayed significantly higher rates of problem behaviours and peer victimization (all, p < 0.001). Left Cornu Ammonis 3 (CA3) volume was a positive predictor of levels of peer victimization (all, p < 0.013). Left CA3 volume was a positive predictor of WM and left Cornu Ammonis 4 (CA4) volume was a negative predictor (all, p < 0.025). A cluster analysis revealed that children displaying symptoms of hyperactivity-impulsivity are the most at risk for peer victimization. Conclusions Interventions focusing on minimizing peer victimization may aid in mitigating adverse downstream effects, and aid in promoting brain health and cognitive function.