I read about
this study a little while ago:
The researchers conducted a genetic linkage analysis of the families and identified chromosomal regions that could contain genes that influence the development of BPD. Trull found the strongest evidence for a genetic influence on BPD features on chromosome nine.
And from a previous study also mentioned in the same article:
The research team found that 42 percent of variation in BPD features was attributable to genetic influences and 58 percent was attributable to environmental influences
So almost half nature and half nurture.