The cause of borderline personality disorder (BPD) remains unclear. The disorder appears to have a genetic component because BPD is about five times more common in people who have a family medical history of the disorder. In addition, scientists believe that chemical imbalances in the brain and other biological factors may play a role in the disorder. For example, research has revealed that people prone to impulsive aggressiveness – such as appears in emotional outbursts associated with BPD – may have impaired neural circuits in the brain. These impairments may leave the person unable to properly control behavior and emotions.

Some experts also believe that abuse, neglect or other childhood traumas may lay the groundwork for the development of BPD. For example, 40 to 71 percent of BPD patients report having been sexually abused, according to the National Institute of Mental Health. According to this theory, events later in life trigger the onset of BPD in adults who experienced this type of stress as children. Personal histories of neglect, hostile conflict, and early parental loss or separation are closely associated with BPD later in life. Children who have head injuries also appear to have a greater risk of developing BPD.