Wechsler Intelligence Scale for Children-Fourth Edition and CNS Vital Signs in a child and adolescent psychiatric sample: a transdiagnostic perspective on capacity-performance dissociation

Aims: This study examined the relationship between general cognitive capacity assessed by the Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV) and process-based neurocognitive performance assessed by central nervous system (CNS) Vital Signs, including capacity-performance dissociation, in a transdiagnostic child and adolescent psychiatric sample. Methods: This retrospective cross-sectional study included 140 children and adolescents (ages 8-16). The relationships between the WISC-IV Full-Scale IQ (FSIQ) and index scores and the CNS Vital Signs (CNSVS) Neurocognitive Index and domain scores were examined. Hierarchical multiple linear regression analysis was used for the statistical analysis. The capacity-performance dissociation was assessed using both a clinical cutoff value (85) and a regression-based standardized residual approach. Results: After adjustment for age and gender, FSIQ was positively associated with multiple CNSVS domains, with the strongest correlation observed for processing speed (r=0.45). The WISC-IV Processing Speed Index was the most consistent independent predictor of neurocognitive performance. Regression-based analyses showed sample-relative lower-than-expected process based performance in 18.6% of participants (n=26). The distribution of regression-based dissociation groups did not differ significantly according to ADHD diagnosis in the overall sample (χ²=1.37, p=0.505). However, among children with normal cognitive capacity (FSIQ≥90), lower-than-expected performance was more frequent in those with ADHD (14/61, 23.0%) than in those without ADHD (1/25, 4.0%; Fisher’s exact p=0.057). In multivariable Firth penalized logistic regression, the ADHD estimate remained positive but imprecise and did not reach statistical significance (OR=4.09, 95% profile-likelihood CI: 0.89-38.64, p=0.106). Conclusion: WISC-IV and CNSVS were moderately associated but assessed distinct aspects of cognition. A subgroup of children with normal cognitive capacity showed process-based neurocognitive performance that was lower than expected relative to the clinical sample-based prediction. A statistically significant independent association with ADHD was not demonstrated, but the imprecision of the estimate did not exclude a potentially meaningful association. Combining general intelligence assessment with process-based neurocognitive measures may provide clinically valuable complementary information.