ADHD Symptom Severity and Oppositional Defiant Behavior: Divergent Structural Pathways Across Clinical and Non‐Clinical Populations—A Multi‐Group Path Analysis Investigation

ABSTRACT Background Attention‐deficit/hyperactivity disorder (ADHD) affects 5%–7% of school‐aged children globally and is characterized by a 40%–60% comorbidity rate with oppositional defiant disorder (ODD). Irritability has emerged as a key transdiagnostic construct linking ADHD severity to oppositional defiant behavior (ODB); however, whether the structural pattern of associations among these constructs differs across clinical and non‐clinical populations remains unexamined. Purpose This study employed multi‐group path analysis within the SEM framework to test whether the structural pathways linking ADHD symptom severity, child irritability, and ODB are invariant across a Clinical ADHD Group ( n = 42) and a Healthy Control Group ( n = 43; total N = 85). Maternal psychological distress was controlled as an exogenous covariate across all groups. Methods A cross‐sectional design was employed. ADHD severity, child irritability, ODB, and maternal distress were assessed via validated parent‐report instruments (CPRS‐R/S, ARI, BSI). Observed‐variable multi‐group path analysis was performed in R using the lavaan package (Rosseel, 2012) (see Supplementary Material S1 for reproducible code and fit index selection) via a nested model comparison, with omnibus structural invariance evaluated using the Chi‐square difference test (Δ χ 2 ); ODB was regressed on ADHD severity, child irritability, and maternal distress, with the three exogenous variables permitted to covary. Bias‐corrected bootstrapping (2000 resamples) was used for parameter confidence intervals. Results The omnibus test of structural invariance was statistically significant, Δ χ 2 (3) = 10.494, p = 0.015, indicating that the structural associations among the focal constructs differ across groups. In the Healthy Control Group, ODB was most strongly associated with child irritability ( β = 0.636, p < 0.001), with ADHD severity showing a weaker association ( β = 0.358, p = 0.001; R 2 = 0.560). In the Clinical ADHD Group, the pattern differed: ODB was most strongly associated with ADHD symptom severity ( β = 0.667, p < 0.001), whereas the association with irritability was weaker ( β = 0.232, p = 0.044; R 2 = 0.585). Maternal psychological distress was not uniquely associated with ODB in either group. Conclusions Child irritability was the strongest correlate of ODB in neurotypical children, consistent with frustration‐based oppositional expression. In clinical ADHD, oppositional behavior was more strongly associated with ADHD symptom severity than with irritability, a pattern consistent with conceptualizations emphasizing executive dysfunction. These findings carry distinct assessment and intervention implications for psychiatric‐mental health nursing practice.