BackgroundThere have been conflicting reports on whether the length polymorphism in
the promoter of the serotonin transporter gene (5-HTTLPR) moderates the
antidepressant effects of selective serotonin reuptake inhibitors
(SSRIs). We hypothesised that the pharmacogenetic effect of 5-HTTLPR is
modulated by gender, age and other variants in the serotonin transporter
gene.AimsTo test the hypothesis that the 5-HTTLPR differently influences response
to escitalopram (an SSRI) compared with nortriptyline (a noradrenaline
reuptake inhibitor).MethodThe 5-HTTLPR and 13 additional markers across the serotonin transporter
gene were genotyped in 795 adults with moderate-to-severe depression
treated with escitalopram or nortriptyline in the Genome Based
Therapeutic Drugs for Depression (GENDEP) project.ResultsThe 5-HTTLPR moderated the response to escitalopram, with long-allele
carriers improving more than short-allele homozygotes. A significant
three-way interaction between 5-HTTLPR, drug and gender indicated that
the effect was concentrated in males treated with escitalopram. The
single-nucleotide polymorphism rs2020933 also influenced outcome.ConclusionsThe effect of 5-HTTLPR on antidepressant response is SSRI specific
conditional on gender and modulated by another polymorphism at the 5' end
of the serotonin transporter gene.