Minor genetic variants of the dopamine D4 receptor (DRD4) polymorphism are associated with novelty seeking in healthy Japanese subjects

Although an association between the dopamine receptor D4 (DRD4) gene and personality traits had been previously investigated, results from previous studies were not conclusive. This may be due to the method of grouping used, which categorized the gene population into two groups based on the length of the variable number of tandem repeats (VNTR) in exon 3. In the present study, we categorized 616 healthy Japanese subjects into more than two groups by further subdividing the DRD4 48-bp VNTR polymorphism, and compared Temperament and Character Inventory (TCI) scores among the groups. A significant difference was found between the DRD4 48-bp VNTR polymorphism and novelty seeking (p = 0.016). The novelty-seeking scores in the subjects carrying the 5/5 genotype were significantly higher than in those carrying the 2/2 genotype (p = 0.002) or the 4/4 genotype (p = 0.005). However, when the conventional method of grouping was used (i.e., short alleles vs. long alleles), there were no significant associations between the DRD4 VNTR polymorphism and any TCI scores. Our results suggest that minor 5-repeat allele is associated with high novelty-seeking scores in healthy Japanese subjects.