title: Age-of-onset classification of conduct disorder: reliability and validity in a prospective cohort study.
abstract: OBJECTIVE
  To test in a prospective clinical cohort study the reliability and validity of the age-of-onset subtyping of conduct disorder.
  
  
  METHODS
  Participants were adolescents referred to psychiatric clinics who met DSM-III-R criteria for conduct disorder by structured diagnostic interview. Age of onset was the reported age of the first conduct disorder symptom. The reliability of age-of-onset report was tested by assessing agreement within informant on interviews 2 to 4 weeks apart. Age-of-onset groups were compared within informant on rates of correlates and symptom and social functioning outcomes over a period of 3 years.
  
  
  RESULTS
  The reliability of age-of-onset report was low (kappa of 0.1 and 0.4 by adolescent and parent informant, respectively). Although the early-onset group had elevated rates of attention-deficit/hyperactivity disorder, family disadvantage, and aggressive and nonaggressive antisocial behaviors at inclusion, growth curve analysis showed that age-of-onset subtyping had no predictive validity.
  
  
  CONCLUSIONS
  The reliability of ascertainment of age of onset of antisocial behavior requires further study. While age-of-onset subtyping has heuristic value with respect to the study of the causal pathways to conduct disorder, it is premature to use this system in clinic settings.
authors.affiliation: Department of Psychiatry, McMaster University, Hamilton, Ontario, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Sanford
authors.forename: M H
authors.initials: MH
authors.lastname: Boyle
authors.forename: P
authors.initials: P
authors.lastname: Szatmari
authors.forename: D R
authors.initials: DR
authors.lastname: Offord
authors.forename: E
authors.initials: E
authors.lastname: Jamieson
authors.forename: M
authors.initials: M
authors.lastname: Spinner
mesh_terms: D000293:Adolescent; D017668:Age of Onset; D000704:Analysis of Variance; D019955:Conduct Disorder / Q000145:classification* / Q000175:diagnosis* / Q000453:epidemiology; D005260:Female; D006801:Humans; D007407:Interviews as Topic; D008297:Male; D009864:Ontario / Q000453:epidemiology; D011446:Prospective Studies; D011594:Psychometrics; D015203:Reproducibility of Results