Personality genetics.

Although 30-60% of the variance in many personality traits is inherited, until recently little was known about the responsible genes. Preliminary studies of family history in bipolar disorder and of X-linkage of personality traits in color-blindness suggested a "quantitative trait locus" (QTL) approach to the genetics of normal personality. In methodically similar but independent studies of 124 Israeli and 315 American normal volunteers we showed an association between the dopamine D4 receptor gene (D4DR) and the personality trait of novelty seeking. In the Israeli sample we also found an interaction between the D4DR gene and the serotonin 2C receptor gene (5-HT2C) with a marked effect on the trait of reward dependence. Further investigation of genes for personality traits may suggest links between normal personality and psychiatric illness.