Common and Unique Etiological Influences on Personality and Personality Disorders in Youth.

BACKGROUND

Personality and personality disorders (PDs) are closely related constructs, but the nature of their relationship remains uncertain. Dimensional models suggest PDs are extreme manifestations of personality traits. We investigated the etiological links between broad personality factors and dimensional PD factors using quantitative analyses of common and unique genetic and environmental etiological factors affecting both normative and deviant personalities, emphasizing methods to minimize measurement bias.

METHODS

Seven national twin cohorts participated (N = 2,353 twins from 1,188 families), assessing personality traits with questionnaires across three adolescent waves and PD traits via age-19 clinical interviews. Exploratory factor analyses of personality traits and the three-cluster ABC factors of PDs simplified the factor structure of the measures. Biometric twin analyses with Cholesky modeling identified genetic and environmental links among factors.

RESULTS

Factor analysis of personality traits yielded non-resilient, disinhibited, and disaffected factors. PDs fit an emotional/erratic, anxious/fearful, and odd/eccentric factor structure. Phenotypic correlations varied, but the disinhibited factor had minimal relations to specific PD factors. Crucially, approximately one-third of the genetic variance was shared between personality and PDs. However, the majority of genetic variance and all non-shared environmental variance were trait-specific, suggesting predominantly distinct etiological pathways.

CONCLUSION

The significant genetic overlap supports the continuum model; results were bolstered by using broad factors and method triangulation. However, unique genetic and environmental influences point to distinct etiological pathways differentiating personality and PDs. These findings endorse the continuum model yet highlight the need for further research to grasp the complex relationships between personality and PDs.