Borderline personality disorder (BPD) is a mental health condition characterized by instability in moods, self-image, and behavior. People with BPD may have unstable relationships; intense episodes of anger, anxiety, or depression; and impulsive, even self-harming, actions.
You are more likely to develop BPD if a member of your family has the condition, and your risk increases depending on how closely related you are to the person with BPD. The heritability of BPD (the chance that you will inherit the trait) is estimated to be 46%.
Current research supports the theory that there is a large genetic component to whether a person develops BPD. Two genes—DPYD and PKP4—have been identified as increasing a person’s risk of developing BPD.
For example, if your full sibling has BPD, you are 4.7 times more likely to develop it than someone who is unrelated to anyone with BPD. That said, the prevalence of BPD across populations is 1.4% — meaning that you are still more likely to not develop BPD, even though you are at greater risk.
However, first-degree relatives also share environments, which means that these findings do not point solely to genetics. Environmental causes, particularly childhood trauma, abuse, and neglect, also contribute to developing BPD.