title: Characteristics of internalizing and externalizing disorders in medication-naive, clinically referred children with attention deficit hyperactivity disorder, combined type and dysthymic disorder.
abstract: OBJECTIVE
  Internalizing and externalizing disorders are frequently comorbid with attention deficit hyperactivity disorder, combined type (ADHD-CT) and dysthymic disorder (DD) in referred primary school-age children, yet there has been relatively little systematic research of the nature of these comorbid disorders. We describe the characteristics of parent- and child-reported internalizing and externalizing disorders in primary school-age children with ADHD-CT and DD.
  
  
  METHODS
  A cross-sectional study of 45 clinically referred medication naive children with ADHD-CT and DD, examining parent and child reports of internalizing and externalizing disorders, defined categorically and dimensionally.
  
  
  RESULTS
  Generalized anxiety disorder and separation anxiety disorder were increased in the DD groups, whether ADHD-CT was present or not. Major depressive disorder was increased in the ADHD-CT and DD group compared to the ADHD-CT alone and the DD alone groups. Conduct disorder was increased in the ADHD-CT alone group compared to the DD with and without ADHD-CT groups. Verbal and fullscale IQ were increased in the DD groups, whether ADHD-CT was present or not, compared to the ADHD-CT alone group.
  
  
  CONCLUSIONS
  There is emerging evidence that DD and anxiety may represent a different phenotypic expression of a common underlying aetiological process, while the co-occurrence of ADHD-CT and anxiety disorders remains unclear. Only the ADHD-CT and DD group is significantly associated with major depressive disorder, which suggests an additive effect. In contrast, conduct disorder and decreased verbal and fullscale IQ are only associated with the ADHD-CT group, which may suggest a protective effect of DD when comorbid with ADHD-CT. From a research perspective, it is important to confirm these found associations in larger samples derived from epidemiological populations.
authors.affiliation: University of Melbourne, Murdoch Children's Research Institute, Royal Children's Hospital, Flemington Road, Parkville, Melbourne Victoria 3052, Australia.
authors.forename: Michelle
authors.initials: M
authors.lastname: Sanders
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Arduca
authors.forename: Mary
authors.initials: M
authors.lastname: Karamitsios
authors.forename: Marilyn
authors.initials: M
authors.lastname: Boots
authors.forename: Alasdair
authors.initials: A
authors.lastname: Vance
mesh_terms: D000293:Adolescent; D001008:Anxiety Disorders / Q000453:epidemiology; D001289:Attention Deficit Disorder with Hyperactivity / Q000453:epidemiology*; D002648:Child; D015897:Comorbidity; D019955:Conduct Disorder / Q000453:epidemiology; D003430:Cross-Sectional Studies; D003865:Major Depressive Disorder / Q000453:epidemiology; D039721:Diagnostic and Statistical Manual of Mental Disorders; D019263:Dysthymic Disorder / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008297:Male; D012017:Referral and Consultation