Sources of variances in personality change during adolescence

Several studies on twins in recent years have revealed both genetic and environmental contributions to personality stability and change in adulthood. However, knowledge on such contributions during adolescence is limited. The present study examined sources of the variances of intra-individual absolute change in personality during adolescent years in 347 pairs of Japanese twins (270 monozygotic and 77 dizygotic twin pairs). Phenotypic analyses with the difference score model showed statistically significant mean-level increases in neuroticism-related traits. Then we applied the Cholesky decomposition model to the difference score model to examine heritability and environmentality of intra-individual change in personality traits. Biometric analyses revealed that the best-fitting model for adolescent personality included additive genetic and nonshared environmental influences. Heritability estimates of intra-individual personality change ranged approximately from 0.00 to 0.27. These findings suggest that both genetic and environmental effects have substantial roles in the etiology of mean-level personality change in adolescence.