Complex segregation analysis of families ascertained through Gilles de la Tourette syndrome.

Although family and twin studies suggest that genetic factors are involved in the etiology of Tourette syndrome and other related tic disorders, further evidence is needed to demonstrate that the familial transmission is consistent with known genetic factors. We performed a complex segregation analysis that allowed for a variable age of onset of Gilles de la Tourette, other tic disorders and obsessive compulsive phenotype information on 108 extended families, each ascertained through one Tourette proband by using regressive models that are able to incorporate additional explanatory variables and major gene effects. A special version of the S.A.G.E. program, REGTLhunt, was used to explore the likelihood surface of all examined models. Results indicated that the pattern of Tourette and other related tic disorders in our data sample is not consistent with Mendelian inheritance even after modelling explanatory variables such as obsessive compulsive symptomatology.