A - 38 Impact of Working Memory and Processing Speed on Executive Function Performances in Youth with Attention-Deficit/Hyperactivity Disorder and Learning Disorder

Abstract Objective Executive function (EF) differences exist among children and adolescents with comorbid attention-deficit/hyperactivity disorder and learning disorders (ADHD+LD), relative to ADHD or LD alone. The impact of cognitive proficiency (i.e., working memory and processing speed) on EF is unclear across these diagnoses. Method This study investigated relations between cognitive proficiency and EF measures for 360 clinic-referred youth (ages 8–18) diagnosed with ADHD, LD, ADHD+LD, or No Diagnosis of ADHD/LD following neuropsychological evaluation. Two-way ANOVAs determined if WISC-V or WAIS-IV working memory (WMI) or processing speed (PSI) indices moderate the associations between group and D-KEFS performance (i.e., Color-Word Interference, Tower, Verbal Fluency, and Trail Making Tests). Results Results revealed significant interactions between group and WMI or PSI affecting D-KEFS Verbal Fluency Category Switching (F’s = 3.00–3.13, p’s = 0.026–0.031). Better performance on WMI or PSI was associated with better performance on Verbal Fluency Category Switching across groups, but this association was significantly less for ADHD+LD compared to other groups. Positive main effects were observed between WMI or PSI and all D-KEFS measures (F’s = 7.62–84.86, p’s < 0.006). Significant main effects were observed between group and D-KEFS Color-Word Interference Inhibition and Trails Number-Letter Sequencing (F’s = 2.95–3.77, p’s = 0.013–0.035), where No diagnosis performed better than other groups. Conclusions Overall, stronger working memory and processing speed may aid EFs for No diagnosis, ADHD, and LD youth, but not ADHD+LD youth. This may suggest an additive impact of a comorbid diagnosis leading to worse deficits in EFs and that stronger working memory and processing speed may be less protective for youth with comorbid diagnoses. Additional research is warranted.