BPD probably has a substantial genetic basis, although it's not implausible that BPD-leaning parents are more likely to abandon or abuse their children. (Not guaranteed, just more likely!)
Mental illnesses of all kinds, like virtually everything, are heritable. Of course, environment can play into heritability, but it's like the IQ debate... full of Culture War and the science of "why the brain does X thing" is unsettled.
BPD probably does have a strong genetic substrate as well since 25% of people diagnosed with BPD also have ADHD, at least that's what the psychiatrist that diagnosed me with BPD told me when she handed me questionaires for ADHD.
I've researched a lot about BPD therapies and the most promising one -- Schema Therapy -- models heavily BPD as being rooted in abandonment issues in childhood -- and everything I've read rang like hitting a nail on it's head, at least in my case.
Mental illnesses of all kinds, like virtually everything, are heritable. Of course, environment can play into heritability, but it's like the IQ debate... full of Culture War and the science of "why the brain does X thing" is unsettled.