An association study between 5-HTTLPR polymorphism, COMT polymorphism, and Tourette's syndrome.

Several lines of evidence suggest that a genetic component underlies Tourette's syndrome (TS). We investigated both the role of the insertion/deletion polymorphism in the promoter region of the serotonin transporter gene (5-HTTLPR) and that of the Val-158-Met substitution in the catechol-O-methyl-transferase (COMT) gene in conferring susceptibility to TS. Fifty-two TS patients were recruited and compared with a control group of 63 healthy subjects. Neither a genotypic nor an allelic association was found; subdividing TS patients according to clinical variables, such as a co-diagnosis of obsessive-compulsive disorder (OCD) and a positive family history for obsessive compulsive disorder or tics, also failed to reveal a significant association. The lack of significance for 5-HTTLPR and COMT polymorphisms in conferring liability to TS does not exclude a role of different functional polymorphisms in genes coding for serotonergic or dopaminergic structures in the etiology of TS. In fact, TS is a complex disorder and these genes most likely have only a minor genetic effect in its etiology.