Another interest is whether this SNP also affects personality traits related to the reward system in healthy people. To address this issue, we investigated the association between this SNP and data from the TCI, a personality profiling questionnaire, in healthy volunteers (Supplementary Table S10). Intriguingly, among the seven dimensions of the TCI, a significant association was found only for reward dependence (RD) (novelty seeking: β=−0.009055, P=0.2995; harm avoidance: β=0.004317, P=0.6819; RD: β=−0.0175, P=0.03265; persistence: β=−0.007554, P=0.6295; self-directedness: β=−0.01274, P=0.1709; cooperativeness: β=−0.004122, P=0.5302; self-transcendence: β=2.68E−06, P=0.9998; Supplementary Figure S3). The RD value decreased as the copy number of the carried C allele increased among the subjects. The RD value on the TCI was previously shown to be positively correlated with activity of the caudate head,30 which has been shown to be associated with reward processing.31 Although a future confirmatory study is needed, the present data suggest the possibility that this SNP is one of the predisposing factors that partially contribute to the developmental differentiation of personality traits related to RD.
