title: Prevalence of pervasive developmental disorders in children and adolescents with mental retardation.
abstract: BACKGROUND
  Insight into the prevalence of pervasive developmental disorder (PDD) in children and adolescents with mental retardation (MR) is known to be of clinical importance. However, estimating this prevalence is complicated. The literature reports prevalence rates ranging from 3% through 50%. This variation seems to be related to the concepts of PDD under study, the instruments used, and the studied populations. The present study aimed to estimate a reliable prevalence rate of PDD.
  
  
  METHODS
  A total population-based screening with the PDD-MRS and the ABC (n=825) was followed by further assessment of children and adolescents at high risk for PDD according to these instruments, and for controls, with the ADI-R, ADOS-G and a DSM-IV-TR classification (n=188).
  
  
  RESULTS
  The instruments lead to different prevalence rates that range from 7.8% to 19.8%. The differences in the estimated prevalence rates are related to the concept of PDD and the instruments they represent. The DSM-IV-TR prevalence (16.7%) seems to be the most reliable and well-founded estimate, since this prevalence rate is based on information from multiple informants and multiple time periods.
  
  
  CONCLUSIONS
  The reported prevalence rates provide policy makers with an up-to-date and more substantiated guideline for the allocation of resources for children and adolescents with MR and PDD. The height of the prevalence should alert professionals that PDD is widespread in the population with MR.
authors.affiliation: Child & Adolescent Psychiatry, University of Groningen, Groningen, The Netherlands. a.de.bildt@accare.nl
authors.forename: Annelies
authors.initials: A
authors.lastname: de Bildt
authors.forename: Sjoerd
authors.initials: S
authors.lastname: Sytema
authors.forename: Dirk
authors.initials: D
authors.lastname: Kraijer
authors.forename: Ruud
authors.initials: R
authors.lastname: Minderaa
mesh_terms: D000293:Adolescent; D002648:Child; D002659:Child Development Disorders, Pervasive / Q000175:diagnosis / Q000453:epidemiology*; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D006801:Humans; D008607:Intellectual Disability / Q000175:diagnosis / Q000453:epidemiology*; D008297:Male; D015995:Prevalence