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Neurocognitive heterogeneity is increasingly recognized as a valid phenomenon in ADHD, with most estimates suggesting that executive dysfunction is present in only about 33%-50% of these children. However, recent critiques question the veracity of these estimates because our understanding of executive functioning in ADHD is based, in large part, on data from single tasks developed to detect gross neurological impairment rather than the specific executive processes hypothesized to underlie the ADHD phenotype. The current study is the first to comprehensively assess heterogeneity in all three primary executive functions in ADHD using a criterion battery that includes multiple tests per construct (working memory, inhibitory control, set shifting). Children ages 8-13 (M = 10.37, SD = 1.39) with and without ADHD (N = 136; 64 girls; 62% Caucasian/Non-Hispanic) completed a counterbalanced series of executive function tests. Accounting for task unreliability, results indicated significantly improved sensitivity and specificity relative to prior estimates, with 89% of children with ADHD demonstrating objectively-defined impairment on at least one executive function (62% impaired working memory, 27% impaired inhibitory control, 38% impaired set shifting; 54% impaired on one executive function, 35% impaired on two or all three executive functions). Children with working memory deficits showed higher parent- and teacher-reported ADHD inattentive and hyperactive/impulsive symptoms (BF = 5.23 × 10), and were slightly younger (BF = 11.35) than children without working memory deficits. Children with vs. without set shifting or inhibitory control deficits did not differ on ADHD symptoms, age, gender, IQ, SES, or medication status. Taken together, these findings confirm that ADHD is characterized by neurocognitive heterogeneity, while suggesting that contemporary, cognitively-informed criteria may provide improved precision for identifying a smaller number of neuropsychologically-impaired subtypes than previously described.

Objective: Executive function deficits are well-established in ADHD. Unfortunately, replicated evidence indicates that executive function training for ADHD has been largely unsuccessful. We hypothesized that this may reflect insufficient targeting, such that extant protocols do not sufficiently and specifically target the neurocognitive systems associated with phenotypic ADHD behaviors/impairments. Method: Children with ADHD ages 8–12 (M = 10.41, SD = 1.46; 12 girls; 74% Caucasian/Non-Hispanic) were randomized with allocation concealment to either central executive training (CET; n = 25) or newly developed inhibitory control training (ICT; n = 29). Detailed data analytic plans were preregistered. Results: Both treatments were feasible/acceptable based on training duration, child-reported ease of use, and parent-reported high satisfaction. CET was superior to ICT for improving its primary intervention targets: phonological and visuospatial working memory (d = 0.70–0.84). CET was also superior to ICT for improving go/no-go (d = 0.84) but not stop-signal inhibition. Mechanisms of change analyses indicated that CET-related working memory improvements produced significant reductions in the primary clinical endpoints (objectively assessed hyperactivity) during working memory and inhibition testing (indirect effects: β ≥ −.11; 95% CIs exclude 0.0). CET was also superior to ICT on 3 of 4 secondary clinical endpoints (blinded teacher-rated ADHD symptoms; d = 0.46–0.70 vs. 0.16–0.42) and 2 of 4 feasibility/acceptability clinical endpoints (parent-reported ADHD symptoms; d = 0.96–1.42 vs. 0.45–0.65). CET-related gains were maintained at 2–4 month follow-up; ICT-related gains were maintained for attention problems but not hyperactivity/impulsivity per parent report. Conclusions: Results support the use of CET for treating executive function deficits and targeting ADHD behavioral symptoms in children with ADHD. Findings for ICT were mixed at best and indicate the need for continued development/study.

Objective: Executive functions are commonly measured using rating scales and performance tests. However, replicated evidence indicates weak/nonsignificant cross-method associations that suggest divergent rather than convergent validity. The current study is the first to investigate the relative concurrent and predictive validities of executive function tests and ratings using (a) multiple gold-standard performance tests, (b) multiple standardized rating scales completed by multiple informants, and (c) both performance-based and ratings-based assessment of academic achievement-a key functional outcome with strong theoretical links to executive function. Method: A well-characterized sample of 136 children oversampled for ADHD and other forms of child psychopathology associated with executive dysfunction (ages 8 -13; 68% Caucasian/non-Hispanic) completed a counterbalanced series of executive function and academic tests. Parents/teachers completed executive function ratings; teachers also rated children's academic performance. Results: The executive function tests/ratings association was modest (r ϭ .30) and significantly lower than the academic tests/ratings association (r ϭ .63). Relative to ratings, executive function tests showed significantly higher cross-method predictive validity and significantly better within-method prediction; executive function ratings failed to demonstrate improved within-method prediction. Both methods uniquely predicted academic tests and ratings. Conclusion: These findings replicate prior evidence that executive function tests and ratings cannot be used interchangeably as executive function measures in research and clinical applications, while suggesting that executive function tests may have superior validity for predicting academic behavior/achievement.

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