title: The hierarchical factor model of ADHD: invariant across age and national groupings?
abstract: OBJECTIVE
  To examine the factor structure of attention-deficit/hyperactivity disorder (ADHD) in a clinical sample of 1,373 children and adolescents with ADHD and their 1,772 unselected siblings recruited from different countries across a large age range. Hierarchical and correlated factor analytic models were compared separately in the ADHD and sibling samples, across three different instruments and across parent and teacher informants. Specific consideration was given to factorial invariance analyses across different ages and different countries in the ADHD sample.
  
  
  METHODS
  A sample of children and adolescents between 5 and 17 years of age with ADHD and their unselected siblings was assessed. Participants were recruited from seven European countries and Israel. ADHD symptom data came from a clinical interview with parents Parental Account of Childhood Symptoms and questionnaires from parents and teachers (Conners Parent and Teacher).
  
  
  RESULTS
  A hierarchical general factor model with two specific factors best represented the structure of ADHD in both the ADHD and unselected sibling groups, and across informants and instruments. The model was robust and invariant with regard to age differences in the ADHD sample. The model was not strongly invariant across different national groups in the ADHD sample, likely reflecting severity differences across the different centers and not any substantial difference in the clinical presentation of ADHD.
  
  
  CONCLUSIONS
  The results replicate previous studies of a model with a unitary ADHD component and separable specific traits of inattention and hyperactivity/impulsivity. The unique contribution of this study was finding support for this model across a large developmental and multinational/multicultural sample and its invariance across ages.
authors.affiliation: Department of Psychology, York University, Toronto, ON, Canada. mtoplak@yorku.ca
authors.forename: Maggie E
authors.initials: ME
authors.lastname: Toplak
authors.forename: Geoff B
authors.initials: GB
authors.lastname: Sorge
authors.forename: David B
authors.initials: DB
authors.lastname: Flora
authors.forename: Wai
authors.initials: W
authors.lastname: Chen
authors.forename: Tobias
authors.initials: T
authors.lastname: Banaschewski
authors.forename: Jan
authors.initials: J
authors.lastname: Buitelaar
authors.forename: Richard
authors.initials: R
authors.lastname: Ebstein
authors.forename: Jacques
authors.initials: J
authors.lastname: Eisenberg
authors.forename: Barbara
authors.initials: B
authors.lastname: Franke
authors.forename: Michael
authors.initials: M
authors.lastname: Gill
authors.forename: Ana
authors.initials: A
authors.lastname: Miranda
authors.forename: Robert D
authors.initials: RD
authors.lastname: Oades
authors.forename: Herbert
authors.initials: H
authors.lastname: Roeyers
authors.forename: Aribert
authors.initials: A
authors.lastname: Rothenberger
authors.forename: Joseph
authors.initials: J
authors.lastname: Sergeant
authors.forename: Edmund
authors.initials: E
authors.lastname: Sonuga-Barke
authors.forename: Hans-Christoph
authors.initials: HC
authors.lastname: Steinhausen
authors.forename: Margaret
authors.initials: M
authors.lastname: Thompson
authors.forename: Rosemary
authors.initials: R
authors.lastname: Tannock
authors.forename: Philip
authors.initials: P
authors.lastname: Asherson
authors.forename: Stephen V
authors.initials: SV
authors.lastname: Faraone
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D001289:Attention Deficit Disorder with Hyperactivity / Q000453:epidemiology* / Q000523:psychology*; D002648:Child; D002675:Child, Preschool; D005060:Europe / Q000453:epidemiology; D005163:Factor Analysis, Statistical; D005178:Faculty; D005260:Female; D006801:Humans; D007406:Interview, Psychological; D007557:Israel; D008297:Male; D008960:Models, Psychological; D010290:Parents / Q000523:psychology; D035781:Siblings / Q000523:psychology
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