What Causes Borderline Personality Disorder?

There is no known, single, and clear cause of borderline personality disorder, but there are clear risk factors and contributing factors that lead to the development of this mental illness. These include childhood stress and trauma, family history and genetic factors, abnormal neurotransmitter functioning in the brain, and biological changes to structures of the brain related to emotional regulation, aggression, and impulsive behaviors.

What is a Personality Disorder?


BPD is one of several personality disorder types. These are psychological disorders that cause unhealthy thought and behavior patterns. These patterns deeply impact relationships with other people, self-esteem, and the ability to function in school, at work, and in other situations. Someone with a personality disorder often doesn’t realize their thinking is unusual and may blame others for difficulties.

Examples of personality disorders other than BPD include narcissistic personality disorder, paranoid personality disorder, avoidant personality disorder, dependent personality disorder, antisocial personality disorder, schizoid personality disorder, and obsessive compulsive personality disorder, or ocpd. Personality disorder treatment involves therapy and sometimes medication.

Borderline Personality Disorder Symptoms


BPD is a personality disorder that is characterized by unstable moods and emotions, unstable relationships, difficulty developing a sense of self, intense anger or depression, fear of abandonment, and even paranoid thinking and dissociation from reality. The symptoms are long-lasting and cause major impairments, such as an inability to keep a job, or complications such as physical injuries. There are nine characteristic signs of symptoms of BPD. Five of these must be persistent and long-lasting for an individual to be diagnosed with BPD:

  1. Fear of abandonment. This is a near-constant, gripping fear that loved ones, friends, and romantic partners will leave. It often causes needy behaviors that more likely drive people away than keep them close.
  2. Unstable relationships. The fear of abandonment can cause unstable relationships, but it goes deeper than that. A person with BPD tends to develop passionate feelings quickly and have short, rocky relationships.
  3. Distorted self-image. It is difficult to develop a sense of self, so this person may look to others to define who he or she is. Self-image may change often with shifting values, styles, hobbies, and careers.
  4. Impulsive behaviors. A person with BPD often engages in risky behaviors on impulse, such as gambling, overspending, driving under the influence, or having unprotected sex.
  5. Self-harm. Self-injury, like cutting, is common with BPD and may extend to suicidal behaviors or attempts.
  6. Intense mood swings. Emotions can be extreme and swing from one to the other. Episodes of depression or euphoria may last only a few hours before changing to another extreme. It can be difficult to come down from extreme moods.
  7. Feelings of emptiness. People with BPD describe feeling empty or like they are nobody and have nothing inside.
  8. Uncontrollable anger. Quick, uncontrollable rage is typical, and it may be directed at oneself or at others. It is challenging for someone with BPD to be able to level out again after these feelings of intense anger.

Paranoia or dissociation. BPD can cause symptoms of psychosis, or detachment from reality that may manifest as paranoid or suspicious thoughts, or a feeling of dissociation from one’s body.

Known Risk Factors for BPD


There are unfortunately no known single causes of BPD, and there is no borderline personality test that can determine with certainty that someone has the condition. From studies of individuals who have been diagnosed with BPD, researchers have uncovered some clear risk factors. These do not determine with certainty that someone will develop BPD, but they significantly increase the risk:

  • Family history. A person with one or more family members is at an increased risk for BPD. This is especially true, and the risk is increased even more, if the family members are parents or siblings.
  • Certain personality traits. In most cases of BPD, signs of the disorder begin to show up in adolescence. A child with certain personality traits, such as impulsivity and aggression, are more likely to develop BPD than a child who is less impulsive and less aggressive.
  • Stress in childhood. Environmental factors in childhood can also put someone at a greater risk of developing BPD. Abuse, neglect, parental divorce, separation from a parent or caregiver, mental disorders in a caregiver, parent, or sibling, or general conflict, fighting, and instability in the family can all cause stress and increase the risk of having a personality disorder later.

It is also known that this kind of stress in the home, family, or relationships can worsen symptoms of BPD. If an adolescent is already showing signs of the condition, this stress can make them worse or can trigger an earlier onset of the diagnosable disorder.

Genetics as a Cause of BPD


Researchers have also looked for biological and genetic causes or contributing factors for BPD. It may be that it is never possible to pinpoint a single cause, but genes or changes in the brain may work together and with other risk factors to trigger the condition.

There is a strong known connection between genetics and BPD. Having a first-degree family member with BPD increases the risk of developing the condition by a factor of five. Studies of identical twins, who share the same genes, have shown that if one twin has BPD the other has a greater than 66 percent chance of also having BPD. This is significant and points to a definite genetic link that may one day be considered a true cause if a gene or multiple genes can be singled out. Currently there is no known gene for borderline personality disorder.

The Role of the Brain in BPD


The structure of the brain and the signaling chemicals, known as neurotransmitters, that work in the brain, have also been implicated in the development of BPD. In imaging studies of the brains of individuals with BPD, researchers have seen changes in structure as compared to the brains of people without a personality disorder. These changes are seen in specific parts of the brain related to symptoms of BPD:

  • Prefrontal cortex. This part of the brain plays a role in decision making and in planning and whether an individual tends to be impulsive or not.
  • Amygdala. The amygdala is crucial for regulating emotions, particularly anxiety, aggression, and fear.
  • Hippocampus. This part of the brain is responsible for self-control and the regulation of behaviors.

Alterations in these parts of the brain can help explain some of the symptoms of BPD, but why the changes have occurred in some people is not known. It is also not known why some people may have alterations in these structures but not develop BPD. Changes in how neurotransmitters function in the brain have also been seen in individuals with BPD. In particular, serotonin, which affects mood, has been seen to function abnormally.

The Role of Trauma in Borderline Personality Disorder


Stress in childhood is considered a risk factor for BPD. Some of these stressful situations may actually be considered trauma, such as abuse or neglect or the death of a parent. One study of trauma and personality disorders found that there is a strong link between these experiences and the mental disorders. For borderline personality disorder, an especially strong connection was found between the development of the disorder and childhood sexual abuse.

Other studies that did not necessarily look at BPD but investigated the connection between childhood trauma and the brain have found that these traumatic experiences do change structures in the brain. Specifically, the experiences of childhood trauma can cause lasting changes in those parts of the brain—the amygdala, hippocampus, and prefrontal cortex—that have also been implicated in BPD.

While a single and clear cause of borderline personality disorder has not been discovered, it is clear that there are a number of factors involved in its development. Trauma, genetics, brain changes, neurotransmitters, and personality all seem to come together to, if not cause, at least contribute to borderline personality disorder in some individuals. Researchers continue to uncover risk factors and potential causes that contribute to BPD. With a greater understanding of how this disease develops, better treatments can also be developed to help individuals live more satisfying lives with a better sense of self and more stable relationships.