A twin study of the common heritable contributions to low-risk trauma, high-risk trauma, posttraumatic stress disorder, and borderline personality disorder

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] The comorbidity of borderline personality disorder (BPD) and posttraumatic stress disorder is common and yet not well understood, particularly outside of treatment-seeking samples. It has been suggested that a shared genetic liability may account for some of the co-occurrence of these two disorders, yet no prior behavioral-genetic findings exist in the literature to directly support this suggestion. The present study aimed to fill this gap in the literature by utilizing data from the Childhood Trauma Study (CTS; Nelson et al., 2002; Nelson et al., 2006; Nelson, Lynskey, Heath, Madden, and Martin, 2010) to examine the common heritable contributions to low-risk trauma, high-risk trauma, posttraumatic stress disorder, and borderline personality disorder features in a general population twin sample. Structural equation modeling was employed to estimate the genetic and environmental influences on all four of these phenotypes, both individually and together, in a quadrivariate Cholesky decomposition model. Results provide preliminary behavioral-genetic support for the notion of the shared genetic liability across BPD and PTSD. Specifically, the estimated genetic correlation of the BPD features phenotype and PTSD phenotype was 0.57. Additional results from the characterization of trauma exposure in this sample as well as the univariate and quadrivariate twin models also largely supported hypotheses based on the extant BPD and PTSD literature.