Tourette's syndrome and attention-deficit hyperactivity disorder: evidence for a genetic relationship.J Clin Psychiatry. 1993 Sep; 54(9):331-7.JC
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.
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.
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.
These results indicate that ADHD is part of the pleiotropic expression of the Gts gene(s).