title: Familiality of Tourette syndrome, obsessive-compulsive disorder, and attention-deficit/hyperactivity disorder: heritability analysis in a large sib-pair sample.
abstract: OBJECTIVE
  Tourette syndrome (TS) is a neuropsychiatric disorder with a genetic component that is highly comorbid with obsessive-compulsive disorder (OCD) and attention deficit/hyperactivity disorder (ADHD). However, the genetic relations between these disorders have not been clearly elucidated. This study examined the familial relations among TS, OCD, and ADHD in a large sample of TS families.
  
  
  METHODS
  Parent-offspring concordance of TS, OCD, and ADHD was examined in 952 individuals from 222 TS-affected sib-pair families originally collected for genetic studies using logistic regression with generalized estimating equations to control for correlated data. Variance components methods were used to estimate the heritability and genetic and environmental correlations among TS, OCD, and ADHD. Bilineal families where both parents had TS or OCD were excluded.
  
  
  RESULTS
  OCD and ADHD were highly heritable in these TS families. There were significant genetic correlations between TS and OCD and between OCD and ADHD, but not between TS and ADHD. In addition, significant environmental correlations were found between TS and ADHD and between OCD and ADHD. Parental OCD + ADHD was associated with offspring OCD + ADHD.
  
  
  CONCLUSIONS
  This study provides further evidence for a genetic relation between TS and OCD and suggests that the observed relation between TS and ADHD may due in part be to a genetic association between OCD and ADHD and in part due to shared environmental factors.
authors.affiliation: Department of Psychiatry, University of California-San Francisco, 401 Parnassus Ave., San Francisco, CA 94143-0984, USA. cmathews@lppi.ucsf.edu
authors.forename: Carol A
authors.initials: CA
authors.lastname: Mathews
authors.forename: Marco A
authors.initials: MA
authors.lastname: Grados
mesh_terms: D001289:Attention Deficit Disorder with Hyperactivity / Q000453:epidemiology / Q000235:genetics; D015897:Comorbidity; D004777:Environment; D005190:Family / Q000523:psychology*; D006801:Humans; D040582:Inheritance Patterns; D009771:Obsessive-Compulsive Disorder / Q000453:epidemiology / Q000235:genetics; D011569:Psychiatric Status Rating Scales; D012307:Risk Factors; D012494:Sampling Studies; D012720:Severity of Illness Index; D035781:Siblings; D005879:Tourette Syndrome / Q000453:epidemiology / Q000235:genetics