Background: Data from epidemiological genetic studies suggest that variability in personality traits is explained, at least partly, by genetic factors. Recently, a growing number of molecular genetic studies have suggested the involvement of the serotonin system in specific traits.
Objective: To investigate the association between three serotonergic polymorphisms [A-1438G (rs6311) of the HTR2A gene, and STin2 VNTR and 5-HTTLPR of the SLC6A4 gene] and personality traits assessed with the Temperament and Character Inventory.
Materials and methods: Four hundred and four unrelated healthy volunteers [50% males, mean age (standard deviation)=40.5 (11.3)] from Asturias (northern Spain) were genotyped using standard methods. Cloninger's Temperament and Character Inventory was used for investigation of temperament and character traits.
Results: The genetic variants were in Hardy–Weinberg equilibrium and genotypic frequencies were similar in both the sexes. 5-HTTLPR was associated with a direct effect on self directedness (F=6.20, P=0.002), and interacting with educational level (F=3.10, P=0.016) and A-1438G (F=3.34, P=0.011) with respect to novelty seeking. STin2 VNTR interacted with age in relation to reward dependence (F=2.74, P=0.013) and with sex in relation to cooperation (F=5.10, P=0.007). In addition, SLC6A4 haplotypes had significant effects on harm avoidance (lower in volunteers with L12), self directedness (higher in volunteers with L12), and self transcendence (higher in volunteers with S10).
Conclusion: Our findings suggest a strong genetic component in personality traits manifested primarily through interaction effects that occur between genetic factors alone and between genetic and demographic factors.