Tourette Syndrome (cont.)
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Is Tourette syndrome inherited?
Evidence from twin and family studies suggests that Tourette syndrome is an inherited disorder. Although early family studies suggested an autosomal dominant mode of inheritance (an autosomal dominant disorder is one in which only one copy of the defective gene, inherited from one parent, is necessary to produce the disorder), more recent studies suggest that the pattern of inheritance is much more complex. Although there may be a few genes with substantial effects, it is also possible that many genes with smaller effects and environmental factors may play a role in the development of Tourette syndrome. Genetic studies also suggest that some forms of ADHD and OCD are genetically related to Tourette syndrome, but there is less evidence for a genetic relationship between Tourette syndrome and other neurobehavioral problems that commonly co-occur with Tourette syndrome. It is important for families to understand that genetic predisposition may not necessarily result in full-blown Tourette syndrome; instead, it may express itself as a milder tic disorder or as obsessive-compulsive behaviors. It is also possible that the gene-carrying offspring will not develop any Tourette syndrome symptoms. The sex of the person also plays an important role in Tourette syndrome gene expression. At-risk males are more likely to have tics and at-risk females are more likely to have obsessive-compulsive symptoms. People with Tourette syndrome may have genetic risks for other neurobehavioral disorders such as depression or substance abuse. Genetic counseling of individuals with Tourette syndrome should include a full review of all potentially hereditary conditions in the family.