Borderline Personality Disorder is something I began reading about decades ago when working on my counseling degree. Unfortunately, there was no real scientific research on BPD at the time.  Everything I read in the DSM about the possible causes of BPD was based on the belief that those who suffered with BPD had caregivers who abandoned, abused, or neglected them in some way during childhood. 

Now, decades later, genetic research has come into play, and has given us some promising data that there is a genetic component to Borderline Personality Disorder.  Other research has suggested that there is a neurological basis for some of the symptoms, that brain chemicals helping regulate mood may not function properly in individuals diagnosed with BPD. Environmental factors, such as traumatic life events – physical or sexual abuse during childhood, neglect, and separation from parents—are at increased risk of developing BPD. https://www.nami.org/About-Mental-Illness/Mental-Health-Conditions/Borderline-Personality-Disorder

For those who may not have heard of Borderline Personality Disorder, it is a mental health disorder that impacts the way you think and feel about yourself and others, causing problems functioning in everyday life. It includes self-image issues, difficulty managing emotions and behavior, and a pattern of unstable relationships. A person with BPD may have an intense fear of abandonment or instability, and may have difficulty tolerating being alone. However, inappropriate anger, impulsiveness and frequent mood swings may push others away, even though those with the disorder want to have loving and lasting relationships.  https://www.mayoclinic.org/diseases-conditions/borderline-personality-disorder/symptoms-causes/syc-20370237

A clinical trial, published in June, 2019 (issued in March, 2021), gives us the first ‘total-population’ study of familial aggregation (occurrence of a trait shared by family members) and heritability of clinically diagnosed BPD. The study followed 1,851,755 individuals born between 1973–1993, in linked Swedish national registries.

This study concluded that the familial aggregation and heritability of Borderline Personality Disorder was estimated at 46%, with the remaining variance explained by non-shared environmental factors. Further studies are necessary in order to learn more about genetic factors and BPD. The time is ripe for identifying genetic variants associated with BPD through large scale genome-wide studies.  This will aide in helping to identify environmental risk factors, and how these may correlate or interact to increase the risk of BPD.  https://www.nature.com/articles/s41380-019-0442-0