hi yes I definitely think theres a hereditary compoenent. I am often struck by many people from my extended family have symptoms of emotional instability and dysregulation. I think I read BPD has a 30–40% genetic basis. Although my own opinion is that while emotional instability and behavioural impulsivity are probably passed down through genetics, the more destructive behaviours like overdosing, substance abuse, and suicidality are more likely to arise from traumatic experiences. I agree though, both DTD and BPD are either/or diagnoses, and seem unable to fully pin down the condition. Hopefully in the next decades more research will help us determine whats going on!