Although Cloninger proposed that HA, NS and RD were influenced by the serotonergic system, the dopamine system and the noradrenaline system, respectively,16 genetic evidence to support this assertion has been mixed, and a recent large meta-analysis of the 5–HTTLPR polymorphism and HA showed no association.17 Only a single GWAS of the TCI has been reported to date. Verweij et al.18 tested all four TCI temperament scales for association with ∼1.2M SNPs in a sample of 5117 Australians, employing single-marker analyses, gene-based tests and pathway analyses, and did not identify any genetic variants to be genome-wide significant.
