Allelic variation in the serotonin transporter promoter affects neuromodulatory effects of a selective serotonin transporter reuptake inhibitor (SSRI)

Abstract
Antidepressant efficacy of selective serotonin reuptake inhibitors (SSRIs) has been shown to depend on functional polymorphisms within the promoter region of the serotonin transporter gene (5-HTTLPR). This gene gives rise to a biallelic polymorphism designated long (l) and short (s). Homozygosity for the long variant (ll-genotype) is associated with a two times more efficient 5-HT uptake compared to the s/l- or s/s-genotype. Paired pulse transcranial magnetic stimulation is a feasible tool in detecting changes of motor cortex excitability induced by SSRIs.