Article

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: 10.25). 07/2005; 57(11):1336-46. DOI: 10.1016/j.biopsych.2005.02.006
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ABSTRACT 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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    • "First of all, WM (i.e., the function of actively holding in mind and manipulating information relevant to a goal) is a necessary mechanism for many other complex tasks such as learning, comprehension, and reasoning (Baddeley, 2007). Second, it is assumed that WM deficits are part of the causal pathway to ADHD symptoms (Barkley, 1997; Willcutt et al., 2005). It is estimated that 81% of children with ADHD have a deficit in the working component (central executive) of WM (Rapport et al., 2013), in contrast to the less impaired memory component (phonological and visuospatial storage/rehearsal). "
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    ABSTRACT: The goal of this randomized controlled trial was to replicate and extend previous studies of Cogmed Working Memory Training (CWMT) in children with Attention-deficit/hyperactivity disorder (ADHD). While a large proportion of children with ADHD suffer from academic difficulties, only few previous efficacy studies have taken into account long term academic outcome measures. So far, results regarding academic outcome measures have been inconsistent. Hundred and two children with ADHD between the age of 8 and 12 years (both medicated and medication naïve) participated in current randomized controlled trial. Children were randomly assigned to CWMT or a new active combined working memory-and executive function compensatory training called 'Paying Attention in Class.' Primary outcome measures were neurocognitive functioning and academic performance. Secondary outcome measures contained ratings of behavior in class, behavior problems, and quality of life. Assessment took place before, directly after and 6 months after treatment. Results showed only one replicated treatment effect on visual spatial working memory in favor of CWMT. Effects of time were found for broad neurocognitive measures, supported by parent and teacher ratings. However, no treatment or time effects were found for the measures of academic performance, behavior in class or quality of life. We suggest that methodological and non-specific treatment factors should be taken into account when interpreting current findings. Future trials with well-blinded measures and a third 'no treatment' control group are needed before cognitive training can be supported as an evidence-based treatment of ADHD. Future research should put more effort into investigating why, how and for whom cognitive training is effective as this would also potentially lead to improved intervention-and study designs.
    Frontiers in Psychology 07/2015; 6. DOI:10.3389/fpsyg.2015.01081 · 2.80 Impact Factor
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    • "With regard to cognitive flexibility, several studies found deficits of adults with ADHD in measures of set-shifting and task switching (Halleland et al. 2012; Rohlf et al. 2012; Tucha et al. 2005), which were linked in neuroimaging studies to reduced activation in bilateral inferior frontal cortices (Cubillo et al. 2010). However, even though executive dysfunctions play a prominent role in cognitive theories on ADHD, meta-analyses demonstrated that deficits in measures of cognitive flexibility were small and inconsistent across studies, suggesting that set-shifting may be a poor candidate for a primary neuropsychological deficit in ADHD (Hervey et al. 2004; Willcutt et al. 2005). Furthermore , the non-significant differences between groups of the present study may have resulted from a high variability of task performance between participants. "
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    ABSTRACT: Neuropsychological research on adults with ADHD showed deficits in various aspects of attention. However, the majority of studies failed to explore the change of performance over time, so-called time-on-task effects. As a consequence, little is known about sustained attention performance of adults with ADHD. The aim of the present study was therefore to test the hypothesis of sustained attention deficits of adults with ADHD. Twenty-nine adults with ADHD and 30 healthy individuals were assessed on four 20-min tests of sustained attention, measuring alertness, selective attention, divided attention and flexibility. The deterioration of performance over time (time-on-task effects) was compared between patients with ADHD and healthy individuals to conclude on sustained attention performance. Compared to healthy individuals, patients with ADHD showed significant deficits of medium size in selective attention and divided attention. Furthermore, medium sustained attention deficits was observed in measures of alertness, selective attention and divided attention. This study supports the notion of sustained attention deficits of adults with ADHD.
    Journal of Neural Transmission 07/2015; DOI:10.1007/s00702-015-1426-0 · 2.87 Impact Factor
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    • "Statistically significant deficits on working memory and some measures of planning have also been reported for ADHD children when compared to healthy controls (Frazier et al., 2004; Van Mourik et al., 2005; Willcutt et al., 2005). In contrast, measures assessing set-shifting (e.g., trail making, Wisconsin Card Sort) and fluency are more weakly related to ADHD than other executive function tasks (Frazier et al., 2004; Willcutt et al., 2005). This literature also demonstrates that there is a great deal of neuropsychological variability within ADHD groups, with fewer than half of children with ADHD exhibiting significant impairment on any specific executive function task (Nigg, Willcutt, Doyle, & Sonuga-Barke, 2005). "
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    ABSTRACT: Background: ADHD-like symptoms are common in FASD. FASD and ADHD groups both display executive function impairments, however, there is ongoing debate whether the pattern and magnitude of executive function deficits differs between these two types of disorders. Methods: An electronic literature search was conducted (PubMed, PsychInfo; 1972-2013) to identify studies comparing the executive functioning of children with FASD with ADHD or control groups. FASD groups included those with and without dysmorphy (i.e., FAS, pFAS, ARND, and other FASD diagnoses). Effect sizes (Hedges’ g, standardized mean difference) were calculated. Random effects meta-analytic models were performed using the metafor package for R. Results: Fifty-one studies met inclusion criteria (FASD N=2,115; ADHD N=453; controls N=1,990). Children with FASD showed the strongest and most consistent deficits in planning, fluency, and set-shifting compared to controls (Hedges’ g=-0.94, -0.78) and children with ADHD (Hedges’ g=-0.72, -0.32). FASD was associated with moderate to large impairments in working memory, compared to controls (Hedges’ g= -.84, -.58) and small impairments relative to groups with ADHD (Hedges’ g= -.26). Smaller and less consistent deficits were found on measures of inhibition and vigilance relative to controls (Hedges’ g=-0.52, -0.31); FASD and ADHD were not differentiated on these measures. Moderator analyses indicated executive dysfunction was associated with older age, dysmorphy, and larger group differences in IQ. Sex and diagnostic system were not consistently related to effect size. Conclusions: While FASD is associated with global executive impairments, executive function weaknesses are most consistent for measures of planning, fluency, and set-shifting. Neuropsychological measures assessing these executive function domains may improve differential diagnosis and treatment of FASD.
    Journal of Child Psychology and Psychiatry 06/2015; In Press. DOI:10.1111/jcpp.12451 · 5.67 Impact Factor
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