title: Attention-deficit hyperactivity disorder with and without obsessive-compulsive behaviours: clinical characteristics, cognitive assessment, and risk factors.
abstract: OBJECTIVE
  To determine the prevalence of obsessive--compulsive behaviours (OCB) in a clinical sample of children with attention-deficit hyperactivity disorder (ADHD) and to compare ADHD children (with and without OCB) with respect to clinical and cognitive characteristics and risk factors.
  
  
  METHODS
  We compared ADHD children (n = 134) with and without OCB, and we compared all ADHD children with a group of normal control subjects (n = 26) on various clinical, cognitive, and inhibitory control measures; neurobiological and psychosocial risk factors; and family histories of psychiatric illness.
  
  
  RESULTS
  Clinically significant OCB was identified in 11.2% (15/134) of children with ADHD. Comorbid OCB was associated with significantly increased perfectionism, improved teacher ratings of inattention, and a decreased likelihood of having a first-degree relative with ADHD. Comorbid ADHD and OCB may also be associated with increased oppositional behaviour at home and better inhibitory control, though these differences were not statistically significant.
  
  
  CONCLUSIONS
  Comorbid OCB is common in clinically referred children with ADHD and is associated with increased impairment relative to ADHD alone. Further, children with ADHD and OCB may develop symptoms as the result of different genetic and environmental risk factors, compared with children with ADHD only.
authors.affiliation: Neurogenetics Section, Child Psychiatry Program, Centre for Addiction and Mental Health, Toronto, Ontario.
authors.forename: Paul Daniel
authors.initials: PD
authors.lastname: Arnold
authors.forename: Abel
authors.initials: A
authors.lastname: Ickowicz
authors.forename: Shirley
authors.initials: S
authors.lastname: Chen
authors.forename: Russell
authors.initials: R
authors.lastname: Schachar
mesh_terms: D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis / Q000453:epidemiology*; D019958:Attention Deficit and Disruptive Behavior Disorders / Q000175:diagnosis / Q000453:epidemiology; D002648:Child; D003072:Cognition Disorders / Q000175:diagnosis / Q000453:epidemiology*; D039721:Diagnostic and Statistical Manual of Mental Disorders; D006801:Humans; D009483:Neuropsychological Tests; D015588:Observer Variation; D009771:Obsessive-Compulsive Disorder / Q000175:diagnosis / Q000453:epidemiology*; D015995:Prevalence; D012307:Risk Factors; D012720:Severity of Illness Index