What's wrong with Tourette syndrome?

Gilles de la Tourette Syndrome (Tourette Syndrome, TS) and related tic disorders have known fascinated researchers since their initial description around 1884 by the French marquis Georges Albert Edouard Brutus Gilles de la Tourette. Particularly the "cause" of the disorder has been a much sought-after prize, but unfortunately this goal has appeared remarkably elusive. Many clues have been pursued, both genetic and environmental factors, but no compelling major contribution to the pathogenesis of the disease has yet emerged. What's wrong with TS? Is it lack of data or lack of concepts? It should be noted that TS is not unique in this respect. Despite decades of intensive data gathering, many prevalent psychiatric disorders, such as schizophrenia, major depressive disorder or obsessive-compulsive disorder still face a more or less similar situation.