Combined analysis of association between personality traits and three functional polymorphisms in the tyrosine hydroxylase, monoamine oxidase A, and catechol-O-methyltransferase genes

Several molecular genetic studies have been conducted with regard to the association between catecholamine-related genes and personality traits. However, the results of replication studies did not always coincide. One of the possible reasons may be that the effect exerted by the individual gene is small. In the present study, we investigated the association between personality traits and systematic combination of functional polymorphisms in three genes that regulate the metabolism of catecholamines, namely, tyrosine hydroxylase (TH), monoamine oxidase A (MAOA), and catechol-O-methyltransferase (COMT). The (TCAT)n repeat in the TH gene, the promoter variable number tandem repeat (VNTR) in the MAOA gene, and Val158Met in the COMT gene were genotyped in 256 healthy Japanese volunteers. Personality traits were evaluated using the NEO Personality Inventory-Revised (NEO PI-R). As a result, the score for Neuroticism increased, and those for Extraversion and Conscientiousness decreased according to the degree of functional polymorphic change, i.e., the lower synthesis/higher catalysis of catecholamines. A statistically significant difference was observed in the change of Extraversion (p=0.04, after Bonferroni correction). These results may provide evidence for the association between metabolic change of catecholamines and personality traits, which may be due to the additive effect of the three genes.