Beyond DSM subtypes: Neuropsychological evidence against functional distinctions in childhood ADHD

The diagnostic subtypes of Attention-Deficit/Hyperactivity Disorder (ADHD) described in the DSM-5 remain widely used in clinical practice despite increasing evidence of their instability and questionable neurocognitive validity. This study examined whether the inattentive, hyperactive/impulsive, and combined presentations correspond to distinct cognitive profiles in school-aged children with ADHD. A total of 114 children aged 7-12 years with DSM-5 ADHD diagnoses were assessed with a standardized neuropsychological battery targeting executive functions, working memory, verbal fluency, and sustained attention. Subtypes were classified with the parent-report SNAP-IV. Exclusionary comorbidities were ruled out via structured interviews and a DSM-based screening tool. Between-group comparisons employed Kruskal-Wallis tests and Bayesian ANOVAs, and a k-means cluster analysis identified empirical cognitive profiles independent of subtype labels. Results showed no significant differences in 14 of 15 measures (all p > 0.05). Bayesian analyses provided substantial support for similarity (BF₁₀ < 0.33; η² ≤ 0.06), with only phonological fluency showing a modest group effect (H = 9.52, p = 0.009; BF₁₀ = 3.89; η² = 0.084). Cluster analysis yielded two stable profiles (low vs. average-high performance) unrelated to DSM-5 subtypes. These findings challenge the clinical utility of symptom-based subtyping in ADHD and support dimensional, performance-based classification models to guide assessment and individualized intervention.