Although to me it seems that the research on the causes of BPD and various other Personality disorders is still not completely conclusive, here is some information on the current research on the causes of BPD.

Borderline personality disorder, or BPD, is a mental disorder classified by unstable moods, difficulties with interpersonal relationships, and volatile and impulsive behavior, and it is typically diagnosed in early adulthood. Researchers are not positive exactly what causes BPD at this point, but early evidence points to a high likelihood of a combination of genetic and …

Source: What Are the Root Causes of Borderline Personality Disorder? – OPI Living