Validity of the Executive Function Theory of Attention-Deficit/Hyperactivity Disorder: A Meta-Analytic Review

University of Denver, Denver, Colorado, United States
Biological Psychiatry (Impact Factor: 10.26). 07/2005; 57(11):1336-46. DOI: 10.1016/j.biopsych.2005.02.006
Source: PubMed


One of the most prominent neuropsychologic theories of attention-deficit/hyperactivity disorder (ADHD) suggests that its symptoms arise from a primary deficit in executive functions (EF), defined as neurocognitive processes that maintain an appropriate problem-solving set to attain a later goal. To examine the validity of the EF theory, we conducted a meta-analysis of 83 studies that administered EF measures to groups with ADHD (total N = 3734) and without ADHD (N = 2969). Groups with ADHD exhibited significant impairment on all EF tasks. Effect sizes for all measures fell in the medium range (.46-.69), but the strongest and most consistent effects were obtained on measures of response inhibition, vigilance, working memory, and planning. Weaknesses in EF were significant in both clinic-referred and community samples and were not explained by group differences in intelligence, academic achievement, or symptoms of other disorders. ADHD is associated with significant weaknesses in several key EF domains. However, moderate effect sizes and lack of universality of EF deficits among individuals with ADHD suggest that EF weaknesses are neither necessary nor sufficient to cause all cases of ADHD. Difficulties with EF appear to be one important component of the complex neuropsychology of ADHD.

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Available from: Joel Thomas Nigg, May 27, 2015
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    • "The mindfulness training was adapted from the MBCT protocol developed for recurrent depression (Segal et al., 2002). The frequency of the sessions was extended from 8 to 12 weekly sessions to offer more repetition of both exercises and didactic teaching, because of common deficits in executive functioning in patients with ADHD (Willcutt et al., 2005). The duration of the sessions was extended with a break of 15 to 30 min halfway the session to make it easier for patients to sustain their attention during the meeting. "
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    ABSTRACT: Objective: The aim of this study was to examine the effectiveness of mindfulness as a treatment for adults diagnosed with ADHD. A 12-week-adapted mindfulness-based cognitive therapy (MBCT) program is compared with a waiting list (WL) group. Method: Adults with ADHD were randomly allocated to MBCT (n = 55) or waitlist (n = 48). Outcome measures included investigator-rated ADHD symptoms (primary), self-reported ADHD symptoms, executive functioning, depressive and anxiety symptoms, patient functioning, and mindfulness skills. Results: MBCT resulted in a significant reduction of ADHD symptoms, both investigator-rated and self-reported, based on per-protocol and intention-to-treat analyses. Significant improvements in executive functioning and mindfulness skills were found. Additional analyses suggested that the efficacy of MBCT in reducing ADHD symptoms and improving executive functioning is partially mediated by an increase in the mindfulness skill "Act With Awareness." No improvements were observed for depressive and anxiety symptoms, and patient functioning. Conclusion: This study provides preliminary support for the effectiveness of MBCT for adults with ADHD.
    Journal of Attention Disorders 11/2015; DOI:10.1177/1087054715613587 · 3.78 Impact Factor
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    • "Collectively, although previous non-meta-analytic (e.g., Aman et al., 1998; Daugherty et al., 1993; Nigg et al., 2002; Schachar et al., 2000) and meta-analytic reviews (e.g., Alderson et al., 2007; Huang-Pollock et al., 2012; Lijffijt et al., 2005; Lipszyc & Schachar, 2010; Oosterlaan et al., 1998; Willcutt et al., 2005) have examined rapid-response impulsivity, the current review is the first to use meta-analytic methods to comprehensively examine choice-impulsivity in children and adolescents with and without ADHD. The current review also addresses limitations of previous reviews by (1) including studies that utilized the two most widely-recognized experimental measures of choice-impulsivity (delay of gratification and delay discounting); (2) including children and adolescents (ages 3 to 17-years); (3) providing an overall between-group effect size; and (4) using a subset of studies to examine differences in between-group effect sizes across several theoretically-based sample and methodological variables. "
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    ABSTRACT: Impulsive behavior is a core DSM-5 diagnostic feature of attention-deficit/hyperactivity disorder (ADHD) that is associated with several pejorative outcomes. Impulsivity is multidimensional, consisting of two sub-constructs: rapid-response impulsivity and reward-delay impulsivity (i.e., choice-impulsivity). While previous research has extensively examined the presence and implications of rapid-response impulsivity in children with ADHD, reviews of choice-impulsive behavior have been both sparse and relatively circumscribed. This review used meta-analytic methods to comprehensively examine between-group differences in choice-impulsivity among children and adolescents with and without ADHD. Twenty-eight tasks (from 26 studies), consisting of 4320 total children (ADHD=2360, TD=1,960), provided sufficient information to compute an overall between-group effect size for choice-impulsivity performance. Results revealed a medium-magnitude between-group effect size (g=.47), suggesting that children and adolescents with ADHD exhibited moderately increased impulsive decision-making compared to TD children and adolescents. Further, relative to the TD group, children and adolescents with ADHD exhibited similar patterns of impulsive decision-making across delay discounting and delay of gratification tasks. However, the use of single-informant diagnostic procedures relative to multiple informants yielded larger between-group effects, and a similar pattern was observed across samples that excluded females relative to samples that included females.
    Clinical psychology review 11/2015; DOI:10.1016/j.cpr.2015.11.001 · 7.18 Impact Factor
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    • "However, EF and ADHD are not synonymous and current research has emphasized the heterogeneity in cognitive function observed in the population of children diagnosed with ADHD (Fair et al. 2012). It has been widely hypothesized that this heterogeneity reflects as yet unidentified subpopulations of children with ADHD currently subsumed under the umbrella diagnosis (Willcutt et al. 2005; Halperin & Schulz, 2006), and it is possible that ADHD following exposure to childhood adversity is one of these subpopulations. In this case, we would expect that children with ADHD following institutionalization would not necessarily evidence the same EF deficits often observed in other populations of children with ADHD. "
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    ABSTRACT: Background: Young children raised in institutions are exposed to extreme psychosocial deprivation that is associated with elevated risk for psychopathology and other adverse developmental outcomes. The prevalence of attention deficit hyperactivity disorder (ADHD) is particularly high in previously institutionalized children, yet the mechanisms underlying this association are poorly understood. We investigated whether deficits in executive functioning (EF) explain the link between institutionalization and ADHD. Method: A sample of 136 children (aged 6-30 months) was recruited from institutions in Bucharest, Romania, and 72 never institutionalized community children matched for age and gender were recruited through general practitioners' offices. At 8 years of age, children's performance on a number of EF components (working memory, response inhibition and planning) was evaluated. Teachers completed the Health and Behavior Questionnaire, which assesses two core features of ADHD, inattention and impulsivity. Results: Children with history of institutionalization had higher inattention and impulsivity than community controls, and exhibited worse performance on working memory, response inhibition and planning tasks. Lower performances on working memory and response inhibition, but not planning, partially mediated the association between early institutionalization and inattention and impulsivity symptom scales at age 8 years. Conclusions: Institutionalization was associated with decreased EF performance and increased ADHD symptoms. Deficits in working memory and response inhibition were specific mechanisms leading to ADHD in previously institutionalized children. These findings suggest that interventions that foster the development of EF might reduce risk for psychiatric problems in children exposed to early deprivation.
    Psychological Medicine 10/2015; DOI:10.1017/S0033291715002020 · 5.94 Impact Factor
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