Haplotype analysis confirms association of the serotonin transporter (5-HTT) gene with schizophrenia but not with major depression

Serotonin (5‐HT) has been implicated in the pathophysiology of several psychiatric disorders including major depressive disorder (MDD) and schizophrenia (SCZ). The serotonin transporter (5‐HTT) is a major regulator of 5‐HT function. 5‐HTT gene polymorphic variants have been associated with both MDD and SCZ. A case–control design was used for candidate gene‐disease association in 194 MDD patients, 155 schizophrenic psychosis patients, and 246 healthy controls, all North European Caucasians. Four polymorphisms were analyzed in terms of genotype, allele, and haplotype‐based associations. Linkage disequilibrium (LD) analysis was also carried out. Bonferroni correction was used for multiple testing. Haplotype‐based analyses showed significant associations between 5‐HTT and SCZ but not MDD. No single locus associations were observed. In agreement with published meta‐analysis our results indicate that 5‐HTT associates with SCZ but not with MDD. It appears that risk for SCZ maps within a specific 5‐HTT haplotype block. © 2007 Wiley‐Liss, Inc.