Additional evidence for an association between the dopamine D4 receptor (D4DR) exon III repeat polymorphism and the human personality trait of Novelty Seeking

The long alleles (greater than or equal to 6 repeats) of the dopamine D4 dopamine receptor exon III polymorphism have been linked in some, but not all, studies to Novelty Seeking (NS), one of four personality traits defined by Cloninger's tridimensional personality questionnarie (TPQ). In order to further examine the robustness of our original observation we have recruited an additional cohort similar in demographic structure to the original cohort. Although no significant difference in mean NS scores was observed when the new subjects (n = 94) were grouped by presence (NS = 17.83 +/- 1.16) or absence (NS = 16.45 +/- 0.65) of the 7 repeat allele, a significant difference in range of NS scores was observed (non-parametric Moses range test, P = 0.01). The effect of the seven allele was also significant in those individuals scoring highest on NS (>1 standard deviation from the mean; t-test, t = 5.13, P = 0.002). In the expanded cohort (n = 218) a significant effect of the seven allele on NS is demonstrated by both parametric (t = 2.26, P = 0.01) and non-parametric (range test, P = 0.004) statistical tests. The effect is also observed in both principal ethnic groups (Ashkenazi and non-Ashkenazi Jews). In the expanded cohort the effect is significant in female (t = 2.2, P = 0.03, n = 98) but not in male subjects (t = 1.12, P > 0.1, n = 116). We discuss both direct and indirect evidence that in our opinion continues to support a modest role for the long alleles of the dopamine D4 receptor repeat polymorphism in the determination of NS behavior at least in some population groups.