The Neurocognitive Profile of Attention-Deficit/Hyperactivity Disorder: A Review of Meta-Analyses.
Level 3 - non-randomized controlled study
Systematic review and quantitative synthesis of observational case-control meta-analyses.
PubMed 29106438 · doi:10.1093/arclin/acx055
What was done
Systematic review and quantitative meta-synthesis of 34 meta-analyses comparing neurocognitive task performance between individuals with attention-deficit/hyperactivity disorder (ADHD) and typically developing healthy controls. Standardized mean differences (SMDs) across cognitive domains were extracted and analyzed using both unweighted and study-count-weighted approaches, alongside moderation analyses for age and funding source.
What was found
Of 253 extracted SMDs across 34 meta-analyses, 244 (96%) showed superior cognitive performance in control groups compared to ADHD groups, yielding an overall mean effect size of SMD = 0.45 (SD = 0.27). Unweighted domain means ranged from 0.35 (set shifting) to 0.54 (working memory). When weighted by number of included studies, domain means ranged from 0.35 (set shifting) to 0.66 (reaction time variability); domains with weighted SMDs above 0.50 were reaction time variability (0.66), intelligence/achievement (0.60), vigilance (0.56), working memory (0.54), and response inhibition (0.52). Cognitive deficits were moderated by age, showing larger between-group differences in children and adults than in adolescents. Deficit magnitude was also significantly moderated by funding source, with drug-funded meta-analyses reporting larger effect sizes than non-drug-funded meta-analyses.
Why it matters
This umbrella review provides a comprehensive benchmark of cognitive impairment across multiple domains in ADHD, confirming wide-ranging executive and attentional deficits while highlighting significant influence from industry funding and age.
Limits
The total number of individual participants is not reported in the abstract. Synthesizes observational case-control studies subject to residual confounding. The presence of larger effect sizes in pharmaceutical-funded meta-analyses indicates potential sponsorship bias, and the abstract does not report medication washout status or diagnostic subtyping.
Cited by
- supports Increased intra-individual response time variability during tasks is a hallmark feature of individuals diagnosed with ADHD.