title: The factor structure of ADHD in a general population of primary school children.
abstract: OBJECTIVE
  To examine whether a bifactor model with a general ADHD factor and domain specific factors of inattention, hyperactivity and impulsivity was supported in a large general population sample of children. We also explored the utility of forming subscales based on the domain-specific factors.
  
  
  METHODS
  Child mental health questionnaires were completed by both teachers and parents of all children in grades 2-4 in Bergen, Norway. Confirmatory factor analysis was performed on the ADHD items of a modified version of the Swanson, Nolan and Pelham Questionnaire-IV (SNAP-IV) for 6,237 children.
  
  
  RESULTS
  The bifactor model showed very good model fit with a strong general ADHD factor and specific factors for impulsivity and inattention. The subfactors, especially hyperactivity, generated from the SNAP-IV ADHD items conveyed little unique variance in the model.
  
  
  CONCLUSIONS
  The findings in this general population sample with a strong general ADHD factor in the bifactor model supports the view on ADHD as a unitary concept with specific domain factors for inattention and impulsivity, but not for hyperactivity. The bifactor model questions the utility of constructing ADHD subscales by the use of a simple sum score when using the SNAP-IV.
authors.affiliation: Centre for Child and Adolescent Mental Health, Uni Health, Uni Research, Bergen, Norway.
authors.forename: Anne Karin
authors.initials: AK
authors.lastname: Ullebø
authors.forename: Kyrre
authors.initials: K
authors.lastname: Breivik
authors.forename: Christopher
authors.initials: C
authors.lastname: Gillberg
authors.forename: Astri J
authors.initials: AJ
authors.lastname: Lundervold
authors.forename: Maj-Britt
authors.initials: MB
authors.lastname: Posserud
mesh_terms: D001289:Attention Deficit Disorder with Hyperactivity / Q000145:classification / Q000175:diagnosis*; D002648:Child; D005163:Factor Analysis, Statistical; D006306:Health Surveys; D006801:Humans; D009664:Norway / Q000453:epidemiology; D011569:Psychiatric Status Rating Scales / Q000592:standards*; D011594:Psychometrics / Q000295:instrumentation*; D012574:Schools; D011795:Surveys and Questionnaires / Q000592:standards*