Association study of the serotonin transporter gene polymorphism in obsessive-compulsive disorder

The hypothesis implicating the serotonergic system in the pathophysiology o f obsessive-compulsive disorder (OCD) is supported by the therapeutic effic acy of selective serotonin reuptake inhibitors (SSRIs). Since SSRIs act on the serotonin transporter (5-HTT), it has been suggested that the 5-HTT gen e (SCL6A4) could be a good candidate for OCD. The SCL6A4 gene has a 44-bp i nsertion/deletion polymorphism in its promoter region (5-HTTLPR). Previous studies have revealed an association between OCD and the I allele. We analy sed the 5HTTLPR polymorphic system in 115 Mexican OCD patients and 136 cont rols. No significant association was found between I allele and OCD (chi (2 ) = 1.54, d.f. = 1, p = 0.21). Furthermore, we assessed alternative methods that employ family-based designs in a sample of 43 trios. Haplotype-based haplotype relative risk and transmission disequilibrium analysis did not sh ow a preferential transmission of I allele to OCD probands. Our results ind icate the need to analyse larger samples using family-based methods.