Working memory impairments in children with attention-deficit hyperactivity disorder with and without comorbid language learning disorders

Our objectives were to examine whether children with attention-deficit hyperactivity disorder (ADHD) are impaired on one or more components of working memory (WM) independent of comorbid language learning disorders, and whether WM impairments are more strongly related to symptoms of inattention than to symptoms of hyperactivity-impulsivity. Four groups of children participated: ADHD (n = 62); ADHD+RD/LI (n = 32); RD/LI (n = 15); and a typically developing comparison group (n = 34). Four simple and brief measures of WM were used that varied in modality (auditory-verbal; visual-spatial) and processing demands (temporary storage versus manipulation of information). Children with ADHD without comorbid language learning disorders exhibited deficits in visual-spatial storage and verbal and visual-spatial central executive (C.E.) functions that were independent of comorbid psychiatric disorders. Children with language learning disorders, regardless of comorbidity with ADHD, exhibited impairments in both verbal and spatial storage as well as C.E. domains of WM. Symptoms of inattention, but not symptoms of hyperactivity/impulsivity, predicted performance on verbal and visual-spatial C.E. measures independent of age, verbal cognitive ability, and reading and language performance. Findings are consistent with data implicating neuropsychological impairments in ADHD. The dimensional results are also consistent with prior research demonstrating the neuropsychological impairments are more strongly associated with the inattention symptom dimension than with the hyperactive-impulsive dimension.