Relationship of 5-HTTLPR genotypes and depression risk in the presence of trauma in a female twin sample

Several studies have implicated an insertion/deletion polymorphism in the promoter region of the serotonin transporter gene (SLC6A4; 5-HTT) in the development of mood disorders. In the present study of a sample of 247 young adult female twins from Missouri, we examine whether this polymorphism interacts with the effect of adverse life events to increase risk for developing depression. We found a significant interaction between the number of high-activity LA alleles and exposure to trauma (OR = 1.70, P < 0.0001). This differs from previous reports, in that the higher activity genotypes (L-A/L-A, L-A/S, L-A/L-G), rather than the low activity genotypes (S/S, S/L-G, L-G/L-G), are associated with an increased incidence of major depressive disease (MDD) in the presence of environmental trauma. (c) 2007 Wiley-Liss, Inc.