Tourette syndrome is a complex neuropsychiatric disorder that occurs along a phenotypic spectrum that also includes chronic (persistent) motor or vocal tic disorder (chronic tics) and transient (provisional) tic disorder (1). Although Tourette syndrome is highly heritable (2), variants in known Tourette risk genes (e.g., CNTN6, NRXN1, SLITRK1, HDC, and CELSR3) account for fewer than 2% of affected individuals (3–6). Tourette syndrome is highly polygenic, with a demonstrated role for multiple common genetic variants of small effect distributed widely across the genome (7). Thus, genome-wide association studies (8) will be of benefit in further elucidating its underlying genetic etiology.
