Behavioral inhibition and triallelic genotyping of the serotonin transporter promoter (5-HTTLPR) polymorphism

To examine the genetic bases of the behavioral inhibition system (BIS) and the behavioral approach system (BAS), we evaluated the association between the BIS, the BAS, and a functional length polymorphism in the promoter of the serotonin transporter gene (5-HTTLPR) in an unscreened sample of undergraduates (N = 211); analyses were conducted using a two-variant (i.e., biallelic) genotyping and three-variant (i.e., triallelic) genotyping of the 5-HTTLPR polymorphism. People with one or two copies of the low-expressing alleles reported stronger endorsement of the BIS than people who were homozygous for the high-expressing alleles; this association was found for triallelic but not biallelic genotyping of the 5-HTTLPR polymorphism. There was no association between the 5-HTTLPR polymorphism and the BAS scales.