Heterogeneity in ADHD: Neuropsychological Pathways, Comorbidity and Symptom Domains

Abstract

The aim of the present study was to investigate different neuropsychological impairments and comorbid behavioral problems in relation to symptoms of Attention-Deficit/Hyperactivity Disorder (ADHD), studying the independent effects of different functions as well as specific relations to symptoms of hyperactivity/impulsivity and inattention. A community-based sample of school children (n = 182; the higher end of the ADHD symptom range was oversampled) completed neuropsychological tasks designed to measure executive function (EF), state regulation and delay aversion. Behavioral symptoms were measured through parental and teacher ratings of the DSM-IV criteria for ADHD and Oppositional Defiant Disorder (ODD). Both categorical and dimensional analyses were used to acquire a deeper understanding of ADHD. The results supported the notion that EF and state regulation constitute independent pathways to ADHD, primarily to symptoms of inattention. In addition, the present study points to the importance of viewing ADHD as a heterogeneous condition also with regard to the differential impact of neuropsychological functioning and comorbidity on different ADHD symptom groups and the two ADHD symptom domains.

Attention deficit/hyperactivity disorder and comorbid disorders in 6-12 year old girls and boys

“…A possible explanation of the differences in the results of our research and the research by other authors, relating to the hyperactivity subtype, may be found in the characteristics of the test sample (the age of the subjects) and the research instruments (self-assessment compared with assessment by parents and teachers). Internalized psychological problems as comorbid disorders, according to our results, were also found in children identified with the impulsivity subtype and the inattentive subtype, which is in line with the results of research conducted so far (28,52).…”

Context-dependent Dynamic Processes in Attention Deficit/Hyperactivity Disorder: Differentiating Common and Unique Effects of State Regulation Deficits and Delay Aversion

“…Finally, when two distinctly different impairments are studied in the same sample different patients appear to be affected by each one. For instance, the classic paper by Solanto et al, (2001) illustrates this most clearly -DAv and inhibitory control deficits were uncorrelated but yet both were associated with ADHD: Four subgroups of children could be identified -DAv and no inhibitory deficits; inhibitory deficits and no DAv; both deficits and neither deficits (see also Thorell, 2007).More recently, a similar pattern was found for SRD and executive deficits (but not DAv; Wåhlstedt et al, 2009).…”

Attention Deficit Hyperactivity Disorder, Other Mental Health Problems, Substance Use, and Driving: Examination of a Population-Based, Representative Canadian Sample

“…Instead, it suggests the need for more complex broad-based research as ADHD is a complex disorder with heterogeneity in neuropsychological pathways, comorbidities and symptom presentations (Coghill et al 2005;Nigg et al 2005;Toplak et al 2008;Wåhlstedt et al 2009). Driving and collision risk research among those with ADHD also needs to include road safety researchers so that collision risk may better be assessed by including validated methods and measures and other factors known to increase risk, such as drug use.…”