Investigating age differences in the genetic and environmental structure of the tridimensional personality...

In this study we examined cross-sectional age differences in means, phenotypic covariance structure, and the underlying genetic and environmental structure of four personality constructs from Cloninger's personality system: Novelty Seeking (NS), Harm Avoidance (HA), Reward Dependence (RD), and Persistence (PS). Study participants were same-sex female twins between the ages of 50 and 96, drawn from the American Association of Retired Persons (AARP) twin sample. We examined age differences by comparing younger (age 50-65) and older (age 661) cohorts (based on a median split of the sample) and by estimating biometrical model parameters as linear and quadratic functions of continuous age. Results indicated modest, but significant, mean-level declines across this age range for NS, RD, and PS. HA showed no significant mean differences. We found moderate heritability estimates for all of the TPQ higher-order personality dimensions, ranging from 0.16 to 0.62. No significant age differences in the proportion of genetic and environmental influences on the TPQ dimensions were found. For HA, RD, and PS there were no significant age-related differences in total variance. However, for NS we observed a decline in total phenotypic variance across age cohorts.