Genetics of personality dimensions

Personality is the characteristic manner or style of an individual's behaviour, and can be measured by self-report questionnaires. Twin studies have revealed a considerable heritable component that partly accounts for individual differences in personality traits. Recently, common genetic polymorphisms have been associated with specific personality dimensions. In particular, some but not all studies have shown a relationship between the long form of the dopamine D4 receptor and novelty seeking and the short form of the serotonin transporter promoter region with harm avoidance or neuroticism. Evidence has also accumulated that the effect of individual genes is small, consistent with the complexity of personality traits, and it is likely that several individual genes make a modest contribution to the phenotype. Extremes of personality traits also characterize maladaptive behaviours. For example type II alcoholism is characterized by high novelty seeking and low harm avoidance, whereas heroin addicts show both high novelty seeking and high harm avoidance. An interaction between the short form of the serotonin transporter and neuroticism contributes to cigarette smoking. Finally, the behavioural and genetic antecedents of personality can be recognized quite early in development, and polymorphisms contributing to temperament traits are demonstrable in the first year of human development. (C) 2000 Lippincott Williams and Wilkins.