Structure of genetic and environmental risk factors for symptoms of DSM-IV borderline personality disorder.

IMPORTANCE: Previous studies have indicated that the psychopathological dimensions of borderline personality disorder (BPD) are influenced by a unitary liability factor. However, to our knowledge, the underlying etiological nature of the individual criteria for BPD as defined by the DSM-IV has not been explored.
OBJECTIVE: To determine the structure of genetic and environmental risk factors for the symptoms of BPD. DESIGN, SETTING, AND PARTICIPANTS: Multivariate twin study with BPD criteria assessed by personal interview within a general community setting. Participants included 2794 young adults from the Norwegian Institute of Public Health Twin Panel. MAIN OUTCOMES AND MEASURES: The 9 criteria for BPD assessed by the Structured Interview for DSM-IV Personality.
RESULTS: A common pathway model dominated by 1 highly heritable (55%) general BPD factor that strongly influenced all 9 BPD criteria (standardized path coefficients, 0.53-0.79) fit the data best. The model also included 2 additional common liability factors, mainly influencing criteria reflecting the affective and interpersonal dimensions. Both of these were mostly influenced by environmental liability factors (heritability, 29.3% and 2.2%). With 1 exception (criterion 2, unstable and intense relationships), the specific criteria were strongly influenced by environmental factors. Five of the 9 criterion-specific genetic effects were either 0 or negligible. CONCLUSIONS AND RELEVANCE: These results indicate that most of the genetic effects on the individual BPD criteria derive from 1 highly heritable general BPD factor, whereas the environmental influences were mostly criterion specific.