A meta-analysis of working memory impairments in children with attention-deficit/hyperactivity disorder.
OBJECTIVE
To determine the empirical evidence for deficits in working memory (WM) processes in children and adolescents with attention-deficit/hyperactivity disorder (ADHD).


METHODS
Exploratory meta-analytic procedures were used to investigate whether children with ADHD exhibit WM impairments. Twenty-six empirical research studies published from 1997 to December, 2003 (subsequent to a previous review) met our inclusion criteria. WM measures were categorized according to both modality (verbal, spatial) and type of processing required (storage versus storage/manipulation).


RESULTS
Children with ADHD exhibited deficits in multiple components of WM that were independent of comorbidity with language learning disorders and weaknesses in general intellectual ability. Overall effect sizes for spatial storage (effect size = 0.85, CI = 0.62 - 1.08) and spatial central executive WM (effect size = 1.06, confidence interval = 0.72-1.39) were greater than those obtained for verbal storage (effect size = 0.47, confidence interval = 0.36-0.59) and verbal central executive WM (effect size = 0.43, confidence interval = 0.24-0.62).


CONCLUSIONS
Evidence of WM impairments in children with ADHD supports recent theoretical models implicating WM processes in ADHD. Future research is needed to more clearly delineate the nature, severity, and specificity of the impairments to ADHD.
Martinussen
Rhonda
R
Institute of Medical Science, University of Toronto, Toronto, Canada.
Hayden
Jill
J
Hogg-Johnson
Sheilah
S
Tannock
Rosemary
R
D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000523:psychology*; D002648:Child; D002675:Child, Preschool; D006801:Humans; D008569:Memory Disorders; D008570:Memory, Short-Term