title: Neuropsychological performance and attention-deficit hyperactivity disorder subtypes and symptom dimensions.
abstract: OBJECTIVE
  Characterization of clinical heterogeneity in attention-deficit hyperactivity disorder (ADHD) remains controversial. Neuropsychological and cognitive studies provide one type of validation data, but too often have considered only a narrow range of functional domains.
  
  
  METHODS
  The current study examined ADHD subtype and presentation differences across a broad range of neurocognitive domains in a large clinically characterized, community-recruited sample of 498 youth (213 control, 107 ADHD-primarily inattentive [ADHD-PI], 137 ADHD-combined [ADHD-C]), ages 6-17 years. Domains assessed included inhibition, working memory, arousal, processing speed, response variability, and temporal information processing.
  
  
  RESULTS
  Youth with ADHD-C performed worse than youth with ADHD-PI in all domains, consistent with a severity model. Performance among a subgroup with a "restrictive inattentive" presentation indicated potential deficits in processing speed relative to other ADHD-PI youth, but no other effects. When all measures were included in the same model, cognitive control (executive functions, working memory, and memory span), arousal, and response variability each provided uniquely incremental statistical prediction of specific symptom dimensions and of subtype/presentation, but temporal information processing and processing speed did not.
  
  
  CONCLUSIONS
  Results suggest the potential to consolidate multiple neurocognitive theories of ADHD, and that such consolidation will apply across putative clinical subtypes or presentations.
authors.affiliation: Department of Psychology, University of Iowa, IA City, IA 52242, USA. molly-nikolas@uiowa.edu
authors.forename: Molly A
authors.initials: MA
authors.lastname: Nikolas
authors.forename: Joel T
authors.initials: JT
authors.lastname: Nigg
mesh_terms: D000293:Adolescent; D001143:Arousal; D001289:Attention Deficit Disorder with Hyperactivity / Q000145:classification / Q000150:complications* / Q000523:psychology*; D002648:Child; D003072:Cognition Disorders / Q000175:diagnosis* / Q000209:etiology*; D056344:Executive Function; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D007266:Inhibition, Psychological; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology; D009483:Neuropsychological Tests; D011930:Reaction Time