Working Memory and Short-Term Memory Deficits in ADHD: A Bifactor Modeling Approach

Objective: Attention-deficit/hyperactivity disorder (ADHD) has been associated with large magnitude impairments in working memory, whereas short-term memory deficits, when detected, tend to be less pronounced. However, confidence in these findings is limited due to task impurity combined with methodological and statistical limitations of the current evidence base. Method: A well-characterized, clinically evaluated sample of 172 children ages 8-13 years (M = 10.30, SD = 1.42; 72 girls; 64% White/non-Hispanic) were administered multiple, counterbalanced working memory tests. Bifactor-(s-1) modeling was used to characterize the presence and magnitude of central executive working memory, phonological short-term memory, and visuospatial short-term memory deficits in pediatric ADHD. Results: ADHD status was associated with very large magnitude impairments in central executive working memory that are present in most pediatric cases (d = 1.63-2.03; 75%-81% impaired), and these deficits covaried with ADHD inattentive and hyperactive/impulsive symptom severity based on both parent and teacher report. There was also evidence for a unique, albeit significantly smaller, impairment in visuospatial short-term memory (d = 0.60; 38% impaired); however, visuospatial short-term memory abilities did not covary with ADHD symptom severity. There was no evidence linking ADHD with phonological short-term memory deficits across either the dimensional or categorical analyses. Conclusion: These findings provide strong evidence that ADHD is associated with marked central executive working memory deficits that covary with their behavioral symptom presentation across settings. In contrast, visuospatial short-term memory deficits, when present, are likely epiphenomenal, and the most parsimonious conclusion appears to be that phonological short-term memory is intact in pediatric ADHD. Key Points Question: Most children with ADHD have impairments in working memory. However, it is unclear whether they also have reduced short-term memory capacities. Findings: Most children with ADHD have intact short-term memory abilities. In contrast, most children with ADHD exhibit marked impairment in working memory, and only working memory abilities are related to ADHD inattentive and hyperactive/impulsive symptom severity. Importance: These findings further implicate working memory deficits in the behavioral symptoms that define ADHD. In contrast, these findings suggest that reduced short-term memory c