title: Autism spectrum disorders and coexisting disorders in a nationwide Swedish twin study.
abstract: BACKGROUND
  Evidence from twin and molecular genetic studies is accumulating that Autism Spectrum Disorder (ASD) shares substantial etiological factors with other disorders. This is mirrored in clinical practice where ASD without coexisting disorders is rare. The present study aims to examine the range of coexisting disorders in ASD in a genetically informative cohort.
  
  
  METHODS
  Parents of all Swedish 9-year-old twins born between 1992 and 2001 (n = 19,130) underwent a telephone interview designed to screen for child psychiatric disorders, including ASD. To ensure full coverage of child psychiatric disorders, data were also retrieved from population-based health registers. We investigated the coexistence of eight psychiatric disorders known to coexist with ASDs in probands and their co-twins.
  
  
  RESULTS
  Half of the individuals with ASDs (50.3%) had four or more coexisting disorders and only 4% did not have any concomitant disorder. The 'healthy co-twin' in ASD discordant monozygotic twin pairs was very often (79% of boys and 50% of girls) affected by at least one non-ASD disorder. The corresponding figures for ASD discordant dizygotic twin pairs were significantly lower (46% of males and 30% of females).
  
  
  CONCLUSIONS
  Detailed phenotypic descriptions including symptoms of problems associated with a wide range of child psychiatric disorders may aid in unraveling the genetic architecture of ASD and should guide the development of intervention strategies addressing each problem type specifically.
authors.affiliation: Centre for Ethics, Law and Mental Health (CELAM), University of Gothenburg, Mölndal, Sweden.|Gillberg Neuropsychiatry Centre, University of Gothenburg, Gothenburg, Sweden.|R&D Unit, Swedish Prison and Probation Service, Gothenburg, Sweden.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Lundström
authors.affiliation: Departments of Psychiatry and Preventive Medicine, Mount Sinai School of Medicine, New York, NY, USA.
authors.forename: Abraham
authors.initials: A
authors.lastname: Reichenberg
authors.affiliation: Department of Pharmacology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at Göteborg University, Gothenburg, Sweden.
authors.forename: Jonas
authors.initials: J
authors.lastname: Melke
authors.affiliation: Department of Clinical Sciences, Child and Adolescent Psychiatry, Lund University, Lund, Sweden.
authors.forename: Maria
authors.initials: M
authors.lastname: Råstam
authors.affiliation: Centre for Ethics, Law and Mental Health (CELAM), University of Gothenburg, Mölndal, Sweden.|R&D Unit, Swedish Prison and Probation Service, Gothenburg, Sweden.
authors.forename: Nóra
authors.initials: N
authors.lastname: Kerekes
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Paul
authors.initials: P
authors.lastname: Lichtenstein
authors.affiliation: Gillberg Neuropsychiatry Centre, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Christopher
authors.initials: C
authors.lastname: Gillberg
authors.affiliation: Centre for Ethics, Law and Mental Health (CELAM), University of Gothenburg, Mölndal, Sweden.
authors.forename: Henrik
authors.initials: H
authors.lastname: Anckarsäter
mesh_terms: D000067877:Autism Spectrum Disorder / Q000453:epidemiology* / Q000235:genetics*; D002648:Child; D015897:Comorbidity; D004200:Diseases in Twins / Q000453:epidemiology* / Q000235:genetics*; D005260:Female; D006801:Humans; D008297:Male; D012042:Registries / Q000706:statistics & numerical data*; D013548:Sweden / Q000453:epidemiology
keywords: Autism spectrum disorders; comorbidity; genetics; twins