Genetic analysis of Tourette syndrome suggesting major gene effect

Data on Gilles de la Tourette syndrome are analyzed by multiple threshold models in inheritance that incorporate sex effect. The polygenic-multifactorial model is rejected. Single major locus inheritance can account for the data, although many of the occurrences of Tourette are due to nongenetic phenocopies. In both models, males and females share a common genetic environmental liability, but the less prevalent sex, that is, females, has a higher genetic loading for the disorder. The predicted population prevalences in the single major locus model are 2.3% for males and 0.8% for females. The implications for genetic and biological research in Tourette syndrome are discussed.