Family-based association study of the 5-HT transporter gene and schizophrenia.

The gene coding for the 5-HT transporter (5-HTT) is considered as a candidate gene for schizophrenia, because this transporter plays a key role in serotonin neurotransmission. Previous genetic studies focusing on this gene yielded conflicting results, presumably because of stratification biases linked to the case-control association study approach, and the potential genetic and phenotypic heterogeneity of schizophrenia. We investigated the 5-HTTLPR and 17-bp VNTR (variable number of tandem repeats) polymorphisms of this gene in 103 trios using the transmission disequilibrium test. No preferential transmission of either allele of the 17-bp VNTR was observed, but an excess of transmission of the L allele of the 5-HTTLPR polymorphism was detected (p = 0.03). As the haplotype analyses did not improve the strength of the association, our data provide convergent evidence for a significant role of the 5-HTTLPR promoter polymorphism of the 5-HTT gene in the vulnerability to schizophrenia.