Cognitive heterogeneity in adult attention deficit/hyperactivity disorder: A systematic analysis of neuropsychological measurements

Abstract

Attention Deficit / Hyperactivity Disorder (ADHD) in childhood is associated with impaired functioning in multiple cognitive domains: executive functioning (EF), reward and timing. Similar impairments have been described for adults with persistent ADHD, but an extensive investigation of neuropsychological functioning in a large sample of adult patients is currently lacking. We systematically examined neuropsychological performance on tasks measuring EF, delay discounting, time estimation and response variability using univariate ANCOVA's comparing patients with persistent ADHD (N = 133, 42% male, mean age 36) and healthy adults (N = 132, 40% male, mean age 36). In addition, we tested which combination of variables provided the highest accuracy in predicting ADHD diagnosis. We also estimated for each individual the severity of neuropsychological dysfunctioning. Lastly, we investigated potential effects of stimulant medication and a history of comorbid major depressive disorder (MDD) on performance. Compared to healthy adults, patients with ADHD showed impaired EF, were more impulsive, and more variable in responding. However, effect sizes were small to moderate (range: 0.05 – 0.70) and 11% of patients did not show neuropsychological dysfunctioning. The best fitting model predicting ADHD included measures from distinct cognitive domains (82.1% specificity, 64.9% sensitivity). Furthermore, patients receiving stimulant medication or with a history of MDD were not distinctively impaired. To conclude, while adults with ADHD as a group are impaired on several cognitive domains, the results confirm that adult ADHD is neuropsychologically heterogeneous. This provides a starting point to investigate individual differences in terms of impaired cognitive pathways.

Similar Subgroups Based on Cognitive Performance Parse Heterogeneity in Adults With ADHD and Healthy Controls

“…First, we did not observe a distinct profile for reaction time variability in adults. Instead, patients in all three profiles were impaired on this measure, consistent with our earlier findings showing that reaction time variability is consistently increased in adults with ADHD, and has the largest effect size for distinguishing patients from controls (Mostert et al, in press). This also ties in with a recent meta-analysis showing moderate-to-large effect sizes for reaction time variability in children, adolescents, and adults with ADHD (Kofler et al, 2013).…”

“…Coghill, Seth, and Matthews (2014) recently extended these findings by demonstrating that on each cognitive domain (working memory, inhibition, delay aversion, decision making, timing, and variability), only a minority of children with ADHD performed deficiently, despite significant group-level effects on all domains. In line with these studies, our own work has shown that adult ADHD patients are impaired in multiple cognitive domains (attention, working memory, and delay discounting), but with moderate effect sizes and with large variability in the number of neuropsychological tasks on which patients performed deficiently (Mostert et al, in press). This indicates that cognitive heterogeneity is also apparent in adults with ADHD.…”

“…Out of the 21 analyzed variables, of which the original case-control comparison has been published elsewhere (Mostert et al, in press), 17 were included in the final models investigated in the current study. The variable Trailmaking–Part B was highly correlated with the other Trailmaking variables and was therefore excluded from the CFA models.…”

“…Detailed group comparisons between adult ADHD patients and healthy controls on the separate measurements have been reported elsewhere (Mostert et al, in press). Details about tasks and main outcome measures are described in Supplementary Table 1.…”

Functional connectivity in cortico-subcortical brain networks underlying reward processing in attention-deficit/hyperactivity disorder

“…Second, ADHD is characterized by large phenotypic heterogeneity, reflected by differences between subjects in ADHD subtype, symptom severity, and cognitive impairments (Coghill et al, 2014, Mostert et al, 2015, Nigg et al, 2005). This large phenotypic heterogeneity in ADHD might be related to a possible large heterogeneity in the underlying neurobiology.…”