Cognitive, Behavioral, and Physiological Factors Influencing Oppositional Defiant Disorder in Children With ADHD: A Comparative Cross-Sectional Study

Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder in children, often co-occurring with oppositional defiant disorder (ODD), a condition characterized by persistent defiant, angry, and oppositional behaviors. This study aims to explore the cognitive, behavioral, and physiological factors influencing the development of ODD in children with ADHD. We conducted a cross-sectional study involving 351 children aged 6-12 years, including ADHD-only, ADHD + ODD, and neurotypical (NT) controls. Participants were assessed using the Wechsler Intelligence Scale for Children (WISC-IV) for cognitive profiles, Conners Parent Rating Scale (CPRS) and SNAP-IV for behavioral symptoms, and blood biomarkers for thyroid hormones and vitamin D levels. Group comparisons were performed using ANOVA, and multiple linear regression was used to identify predictors of ODD symptoms. We found that children with ADHD + ODD exhibited more severe symptoms across behavioral domains, particularly conduct problems, impulsivity, and emotional dysregulation, compared to those with ADHD alone. Notably, conduct problems (β = 0.547, <i>p</i> < 0.001) and hyperactivity/impulsivity (β = 0.373, <i>p</i> < 0.001) were identified as significant predictors of ODD symptoms, highlighting the role of externalizing behaviors in the development of ODD. However, no significant differences were observed in cognitive function, thyroid function and vitamin D levels between the groups, suggesting that cognitive function and these physiological markers may not be central to the comorbidity of ADHD and ODD. These findings emphasize the critical role of behavioral factors, particularly conduct problems and hyperactivity, in the exacerbation of ODD symptoms in children with ADHD, offering insights for targeted interventions.