title: Association between DRD4 genotype and Autistic Symptoms in DSM-IV ADHD.
abstract: OBJECTIVE
  To explore the association of the DRD4 exon 3 7-repeat allele with clinically significant levels of autistic symptoms among children and adolescents with DSM-IV Attention-Deficit/Hyperactivity Disorder (ADHD).
  
  
  METHODS
  Subjects included in the main analysis were 954 Missouri-born twins from a study of the genetic epidemiology of ADHD with complete data on DSM-IV ADHD diagnosis, DRD4 genotype and the parent-rated Social Responsiveness Scale (SRS). Logistic regression was used to investigate the association of the DRD4 7-repeat allele with clinically elevated SRS score.
  
  
  RESULTS
  Among individuals with DSM-IV ADHD (any subtype), the DRD4 7-repeat allele was associated with high SRS score. The distribution of raw SRS scores appeared bimodal among subjects with at least one copy of the DRD4 7-repeat allele, suggesting a possible interaction between this DRD4 genotype and other, unmeasured variables.
  
  
  CONCLUSIONS
  The DRD4 7-repeat allele may increase the risk for clinically elevated autistic symptoms in children and adolescents with ADHD. Further studies are needed to confirm this finding and explore the role of specific gene-gene and gene-environment interactions in the development of autistic symptoms and other co-occurring psychopathology among individuals with ADHD.
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Angela M
authors.initials: AM
authors.lastname: Reiersen
authors.forename: Alexandre A
authors.initials: AA
authors.lastname: Todorov