title: Comorbid externalising behaviour in AD/HD: evidence for a distinct pathological entity in adolescence.
abstract: While the profiling of subtypes of Attention Deficit Hyperactivity Disorder (AD/HD) have been the subject of considerable scrutiny, both psychometrically and psychophysiologically, little attention has been paid to the effect of diagnoses comorbid with AD/HD on such profiles. This is despite the greater than 80% prevalence of comorbidity under the DSM-IV-TR diagnostic definitions. Here we investigate the event related potential (ERP) and psychometric profiles of Controls, AD/HD, and comorbid AD/HD (particularly AD/HD+ODD/CD) groups on six neurocognitive tasks thought to probe the constructs of selective and sustained attention, response inhibition and executive function. Data from 29 parameters extracted from a child group (age range 6 to 12; 52 Controls and 64 AD/HD) and from an adolescent group (age range 13 to 17; 79 Controls and 88 AD/HD) were reduced via a Principal Components Analysis, the 6 significant eigenvectors then used as determinants of cluster membership via a Two-Step Cluster Analysis. Two clusters were found in the analysis of the adolescent age group--a cluster dominated by Control and AD/HD participants without comorbidity, while the second cluster was dominated by AD/HD participants with externalising comorbidity (largely oppositional defiant/conduct disorder ODD/CD). A similar segregation within the child age group was not found. Further analysis of these objectively determined clusters in terms of their clinical diagnoses indicates a significant effect of ODD/CD comorbidity on a concurrent AD/HD diagnosis. We conclude that comorbid externalising behaviour in AD/HD constitutes a distinct pathological entity in adolescence.
authors.affiliation: Brain Sciences Institute, Swinburne University of Technology, Melbourne, Victoria, Australia.
authors.forename: Sharnel
authors.initials: S
authors.lastname: Perera
authors.forename: David
authors.initials: D
authors.lastname: Crewther
authors.forename: Rodney
authors.initials: R
authors.lastname: Croft
authors.forename: Hannah
authors.initials: H
authors.lastname: Keage
authors.forename: Daniel
authors.initials: D
authors.lastname: Hermens
authors.forename: C Richard
authors.initials: CR
authors.lastname: Clark
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior; D001289:Attention Deficit Disorder with Hyperactivity / Q000453:epidemiology / Q000473:pathology* / Q000503:physiopathology / Q000523:psychology*; D019958:Attention Deficit and Disruptive Behavior Disorders / Q000453:epidemiology / Q000503:physiopathology / Q000523:psychology; D001315:Australia / Q000453:epidemiology; D016022:Case-Control Studies; D002648:Child; D002652:Child Behavior; D016000:Cluster Analysis; D015897:Comorbidity; D019955:Conduct Disorder / Q000453:epidemiology / Q000503:physiopathology / Q000523:psychology; D005071:Evoked Potentials; D006801:Humans; D008297:Male; D025341:Principal Component Analysis