Borderline personality disorder symptoms and stressful life events: An evaluation of gene-environment interplay

Borderline personality disorder (BPD) is associated with high levels of stressful life experiences (SLEs). However, it is unclear if persons experiencing SLEs have more BPD symptoms after accounting for familial risk factors. The present study had two primary aims. First, create an optimal predictive model of BPD using a measure of stressors across age and contexts. Second, examine if SLEs result in higher levels of BPD symptoms over and beyond shared genetic and environmental risk. The sample comprised 2801 twins from the Norwegian Institute of Public Health Twin Panel. Negative binomial Poisson regression was used to explore which SLEs predicted BPD symptoms. Elastic net penalized regression was conducted to develop an optimal predictive model for SLEs and BPD symptoms. Co-twin control analyses were performed to differentiate between environmental and genetic factors. Multiple SLEs, in childhood and adulthood, were associated with BPD symptoms. A weighted poly-event risk score explained 22% of the total variation in BPD symptoms. Shared environmental and heritable factors explained 31% and 47% of individual differences in BPD symptomatology, respectively. Measured SLEs explained 42% of shared environmental risk for BPD. The predictive risk for BPD by SLEs was reduced when accounting for shared environmental and genetic factors. Higher BPD symptomatology following SLE exposure cannot fully be explained by genetic and social background factors. Attenuation of the SLE-BPD symptoms associations was primarily due to selection by family environments. Thus, it is of importance to identify social background factors leading to both SLEs and BPD symptoms.