TS is a genetic condition, meaning it is passed on from parent to child. This does not mean that if someone has TS their son or daughter will also be born with TS. Studies indicate that a person with TS has between a 5-15% chance of having a child, sibling or parent with the condition. Scientists originally thought that TS was carried in a single gene, but it’s now believed that TS involves multiple genes. Though it appears that there is likely to be a significant genetic factor, some studies indicate prenatal, perinatal, autoimmune, and environmental factors may contribute to or modulate the severity of symptoms. More research is required to fully understand the disorder.