title: Clinical and cognitive characteristics of children with attention-deficit hyperactivity disorder, with and without copy number variants.
abstract: BACKGROUND
  Submicroscopic, rare chromosomal copy number variants (CNVs) contribute to neurodevelopmental disorders but it is not known whether they define atypical clinical cases.
  
  
  OBJECTIVE
  To identify whether large, rare CNVs in attention-deficit hyperactivity disorder (ADHD) are confined to a distinct clinical subgroup.
  
  
  METHODS
  A total of 567 children with ADHD aged 5-17 years were recruited from community clinics. Psychopathology was assessed using the Child and Adolescent Psychiatric Assessment. Large, rare CNVs (>500 kb, <1% frequency) were defined from single nucleotide polymorphism data.
  
  
  RESULTS
  Copy number variant carriers (13.6%) showed no differences from non-carriers in ADHD symptom severity, symptom type, comorbidity, developmental features, family history or pre-/perinatal markers. The only significant difference was a higher rate of intellectual disability (24% v. 9%, χ(2) = 15.5, P = 0.001). Most CNV carriers did not have intellectual disability.
  
  
  CONCLUSIONS
  Large, rare CNVs are not restricted to an atypical form of ADHD but may be more highly enriched in children with cognitive problems.
authors: Department of Psychological Medicine and Neurology, and MRC Centre for Neuropsychiatric Genetics, Cardiff University, Cardiff, UK.
authors: Kate
authors: K
authors: Langley
authors: Joanna
authors: J
authors: Martin
authors: Sharifah Shameem
authors: SS
authors: Agha
authors: Charlotte
authors: C
authors: Davies
authors: Evangelia
authors: E
authors: Stergiakouli
authors: Peter
authors: P
authors: Holmans
authors: Nigel
authors: N
authors: Williams
authors: Michael
authors: M
authors: Owen
authors: Michael
authors: M
authors: O'Donovan
authors: Anita
authors: A
authors: Thapar
mesh_terms: D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000453:epidemiology / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D015897:Comorbidity; D056915:DNA Copy Number Variations; D002658:Developmental Disabilities / Q000453:epidemiology / Q000235:genetics*; D005260:Female; D055106:Genome-Wide Association Study; D006801:Humans; D008607:Intellectual Disability / Q000453:epidemiology / Q000235:genetics*; D007361:Intelligence Tests; D007406:Interview, Psychological; D008297:Male; D020641:Polymorphism, Single Nucleotide; D006113:United Kingdom / Q000453:epidemiology