The genetics of obsessive-compulsive disorder and Tourette's syndrome: what are the common factors?

Genetic discovery in obsessive-compulsive disorder and Tourette's syndrome has made significant progress in the past decade. The two disorders are phenomenologically, epidemiologically, and probably pathophysiologically related; however, as with most neuropsychiatric disorders, gene discovery has been challenging. Genetic epidemiology studies support the existence of susceptibility genes in both disorders, and more extensive genome-wide studies are under way. Gene pathways involving neurotransmitter (serotonin, dopamine, glutamate) and neurodevelopment (synaptic, homeobox) domains have been examined, but more complex genetic mechanisms remain largely unexplored. This review addresses the current state of genetic research in obsessive-compulsive disorder and Tourette's syndrome, emphasizing commonalities between the disorders. Questions on common genetic substrates, the use of endophenotypes, and the utility of genetic data to inform pharmacologic treatment are also addressed.