Researchers aren’t sure what causes Borderline Personality Disorder, but studies suggest that genetic, environmental, and biological factors may increase the risk of developing BPD. The intertwining of these biological and environmental factors is referred to as the Biosocial Model. Although these factors may increase a person’s risk, it doesn’t mean it is certain that they will develop borderline personality disorder. Conversely, people without these risk factors may develop the disorder in their lifetime.