Stability and change in genetic and environmental components of personality in old age

Stability and change in the mean levels and sources of variation in personality was examined. A sample of 149 monozygotic and 202 dizygotic twin pairs over 80 years were studied three times with a 2-year interval between measurement occasions. The Eysenck Personality Inventory to measure extraversion and neuroticism was used. Linear mixed models and Cholesky variance decomposition were carried out (age, gender and mortality controlled). High mean level stability was found in extraversion and neuroticism. Mortality was related to lower scores in extraversion and higher scores in neuroticism. In extraversion and neuroticism, genetic effects were moderate. Though no new genetic contributions emerged over time, significant new environmental effects were found over time. Controlling for mortality slightly increased genetic effect in extraversion.