Numerous studies have reported association of the serotonin transporter gene (5-HTT) polymorphisms and neuroticism and traits characterizing sociability and activity. This study aimed to define a single genotype effect of three polymorphic markers in the 5-HTT gene (5-HTTLPR, A/G SNP in 5-HTTLPR and STin2 VNTR) and to check possible association of the 5-HTT haplotypes and personality traits [assessed with Eysenck Personality Inventory (EPI) and Temperament and Character Inventory (TCI) questionnaires] in 301 healthy young individuals.
To investigate single genotype and haplotype effects of all polymorphic markers, multivariate analysis of variance and haplotype trend regression analyses were conducted correspondingly.
Individuals with STin2.10 allele scored significantly lower on Neuroticism (EPI) (P=0.007) and Harm Avoidance (P=0.005) in the overall sample. The same pattern of association was reported in women: carriers of STin2.10 allele scored lower on Harm Avoidance (TCI) (P=0.008). Haplotype trend regression analyses revealed that carriers of S12 haplotype had lower sociability-related traits such as Extraversion (EPI) and Novelty Seeking (TCI), whereas Harm Avoidance (TCI) (anxiety-related trait) was higher. Opposite association was observed for S10 haplotype: Extraversion (EPI) score was higher, whereas Harm Avoidance (TCI) score was lower in carriers of this haplotype.
As single polymorphism effect of STin2 was observed in relation to anxiety-related traits, opposite S10 and S12 haplotype effects on Neuroticism and Harm Avoidance could be explained by the larger impact of STin2 polymorphism. Controversially, we consider that the variance in sociability-related traits is related to specific haplotypes of 5-HTT gene.