Cloninger's temperament and character dimensions and dopaminergic genes: DAT1 VNTR and COMT Val158Met polymorphisms

the objective of this study was to examine the associations between Cloninger temperament and character dimensions with the DAT1 VNTR and COMT Val158Met polymorphisms.

The study was conducted on 101 subjects, consisting of students of the Police College in Zagreb and staff of the Sestre Milosrdnice University Hospital in Zagreb. The Cloninger Temperament and Character Inventory (TCI) was used to test personality traits.

A main effect of the DAT1 VNTR polymorphism was found on the subscale self-directedness - SD2 (F=5.18, df=1, p<0.05), where a higher result was detected in carriers of the 9/9 genotype (M=7.33, SD=0.51) than those carrying the 10-repeat allele (M=6.02, SD=1.36). Also for the COMT Val158Met polymorphism, main effects were found on the subscales: NS3 (novelty seeking) (F=5.18, df=1, p<0.05), where a higher result was found in carriers of the Val allele (M=5.03, SD=2.22) than in carriers of the Met/Met genotype (MD=4.76, SD=2.37), SD3 (self-directedness) (F=5.18, df=1, p<0.05) where a higher result was found in carriers of the Val/Val genotype (M=4.50, SD=0.78) than in those carrying the Met allele (M=3.80, SD=1.31); C3 (cooperativeness) (F=5.18, df=1, p<0.05), where a high result was found in carriers of the Val allele (M=5.68, SD=1.25) than those carrying the Met/Met genotype (M=5.08, SD=1.11); and ST3 (self-transcendence) (F=5.18, df=1, p<0.05), where a higher result was found in carriers of the Met/Met genotype (M=3.46, SD=2.37) than carriers of the Val allele (M=2.69, SD=1.84). Two significant interactions were detected, on the subscale NS3 (novelty seeking) (F=5.18, df=1, p<0.05), and on the subscale C2 (cooperativeness) (F=5.18, df=1, p<0.05).

Cloninger's (1987) hypothesis about negative relationship between novelty seeking and dopamine was confirmed on allele level, because higher novelty seeking was found in Val allele carriers comparing to Met/Met genotype carriers.