title: Tourette's syndrome and attention-deficit hyperactivity disorder: evidence for a genetic relationship.
abstract: BACKGROUND
  Attention deficit disorder with or without hyperactivity (ADD) is present in 49% to 83% of patients with Tourette's syndrome (TS), and up to 50% of children with attention-deficit hyperactivity disorder (ADHD) have chronic tics or a family history of chronic tics. Two explanations have been offered for this association: (1) ADHD is part of the pleiotropic expression of the Gilles de la Tourette (Gts) gene(s), or (2) the presence of ADHD in TS is due to ascertainment bias.
  
  
  METHODS
  To avoid ascertainment bias, we examined 338 first-degree relatives of 131 TS probands utilizing a structured questionnaire and the DSM-III criteria for ADD and DSM-III-R criteria for ADHD. All probands and many relatives were personally interviewed.
  
  
  RESULTS
  Of the relatives with TS, 61% had ADD and 36% had ADHD. Of the relatives with chronic tics, 41% had ADD and 26% had ADHD. Log-linear analysis showed a major, significant association between tics and ADHD.
  
  
  CONCLUSIONS
  These results indicate that ADHD is part of the pleiotropic expression of the Gts gene(s).
authors.affiliation: Department of Medical Genetics, City of Hope National Medical Center, Duarte, CA 91010.
authors.forename: E R
authors.initials: ER
authors.lastname: Knell
authors.forename: D E
authors.initials: DE
authors.lastname: Comings
mesh_terms: D001289:Attention Deficit Disorder with Hyperactivity / Q000453:epidemiology / Q000235:genetics*; D016009:Chi-Square Distribution; D015897:Comorbidity; D005190:Family; D005796:Genes; D006801:Humans; D016014:Linear Models; D008957:Models, Genetic; D010641:Phenotype; D017678:Sex Distribution; D013981:Tic Disorders / Q000453:epidemiology / Q000235:genetics; D005879:Tourette Syndrome / Q000453:epidemiology / Q000235:genetics*