The sample consisted of 952 individuals from 222 affected sibling-pair (ASP) families collected by the Tourette Syndrome Association International Consortium on Genetics (TSAICG) for genetic linkage studies of TS35, 43, 44. Families were included if at least two biological siblings had TS and if both siblings and at least one parent were willing to participate in the genetic studies. Sixty-six percent of families had two siblings, 27% had three siblings, 5.3% had four siblings, and 1.6% had five siblings. Four families included half siblings. Families that were known to be bilineal, i.e. both parents had a known diagnosis of TS, CMVT or OCD, were not recruited for inclusion into the study because the original study design aimed at minimizing genetic heterogeneity. However, families found to be bilineal at the time of the best estimate were not excluded. Families were not routinely excluded based on parental diagnoses of ADHD or subclinical obsessive-compulsive symptoms (OCB), or if only one parent had TS, CMVT, or OCD. Parents and all siblings thought to have a tic disorder were assessed for TS and related tic
