Causes of Borderline Personality Disorder

Borderline personality disorder is a complex condition that emerges from a complicated web of causation. Genetic factors and negative environmental influences from childhood are the primary causes of BPD, and it is highly unlikely that a person will develop borderline personality disorder if one or the other of these factors is lacking. Borderline personality disorder is a brain disease associated with various neurological anomalies, all of which can ultimately be traced to the confluence of genetics and past traumatic experience.

Facts about Borderline Personality Disorder


Borderline personality disorder (BPD) is a formidable mental health condition that impacts every area of an individual’s life. People with BPD have trouble managing their emotions and maintaining their focus, and as a result their behavior, relationships, and self-image tend to be highly unstable.

At one time, BPD was thought to be a relatively unusual condition. But the latest research suggests that borderline personality disorder is much more common than previously realized.

Past estimates put the incidence of the disorder at 1.6 percent of the adult population, but recent studies indicate that up to six percent of the adult population in the United States may meet the criteria for a BPD diagnosis at some point in their lives.

And these numbers don’t tell the whole story. One misconception about BPD is that it is strictly an adult disorder, but the latest research shows it is more widespread among youth than formerly imagined. A 2014 study revealed that 1.4 percent of adolescents met the criteria for a borderline personality disorder by the age of 16, and that number rose steadily to 3.2 percent by the age of 22. Most cases of BPD are diagnosed in young adults, but a significant percentage of these individuals likely would have met the criteria for diagnosis several years earlier, if a thorough evaluation of their symptoms had been made.

Adult traumas might affect BPD sufferers, making their symptoms worse or harder to overcome. But borderline personality disorder does not develop as a result of those traumas. Instead, it is a combination of genetic factors and childhood experiences (early environmental influences) that cause a person to develop borderline personality disorder.

Genetic Factors and Borderline Personality Disorder


Borderline personality disorder does run in families.

An individual with a parent, child, or sibling with BPD is five times as likely to be diagnosed with the disorder than someone who has no such family connection. Borderline personality disorder is a brain disease, and when genetic factors associated with the disorder are present it will inevitably affect brain development in ways that leave a person vulnerable to BPD symptoms.

Traumatic experiences in childhood, which occur at a time when brains are delicate and still in formation, also contribute to these harmful neural deviations. But when a person carries a genetic predisposition for borderline personality disorder, the impact of those environmental factors is amplified by several degrees.

In 2008, a team of European researchers, in partnership with the University of Missouri, carried out an extensive study of more than 5,000 sets of twins to determine whether genetics or environment were more decisive in the development of borderline personality disorder. Overall, they found that 58 percent of the BPD symptoms experienced by study participants could be attributed to genetic factors, while 42 percent could be credited to environmental factors.

Another study published in 2013 in the peer-reviewed journal JAMA Psychiatry confirmed the primacy of genetic factors, which explained the consistency of the symptoms experienced by BPD sufferers far better than any commonalities in childhood exposure to trauma. Two of the most distinctive symptoms of BPD—unstable self-image and instability in relationships—did show a higher level of connection to those early environmental factors. But genetics still made a significant contribution to their development, and inherited traits were the dominant causal factor in the remaining core symptoms (of which there are nine in all).

There is no one gene that causes borderline personality disorder symptoms to manifest. There are likely a number of genetic abnormalities involved in the onset of BPD, and those genetic influences can predispose a person to developing other forms of mental illness as well, including bipolar disorder, depression, ADHD, PTSD, and generalized anxiety disorder.

Co-occurring mental health disorders are common in people diagnosed with BPD, which verifies the generality of the risk for mental illness associated with genetic factors and the changes in brain structure and function they cause.

Environment Influences and Borderline Personality Disorder


Environmental factors, which in this case means exposure to childhood trauma, loss, and neglect, also plays a role in the onset of borderline personality disorder. While genetic influences may be somewhat more important, only a small percentage of BPD sufferers will develop the disorder despite having no past history of abuse and neglect.

Because children are still in a stage of transition, mentally and physically, negative experiences can have a devastating impact on their course of development. They may be diagnosed with numerous mental health problems in later life, including borderline personality disorder.

The list of childhood experiences that make a person vulnerable to BPD in adulthood includes:

  • Emotional abuse
  • Physical abuse
  • Sexual abuse
  • Neglect by parents
  • Separation from parents (death or desertion)
  • Witnessing of abuse within the family

Multiple studies have been carried out investigating the prevalence of childhood abuse and neglect among adult borderline personality disorder sufferers, and the results are striking: between 40 and 86 percent of BPD sufferers report sexual abuse, up to 75 percent say they were emotionally abused, up to 73 percent report physical abuse, and between 17 and 25 percent experienced severe emotional neglect.

Children depend on parents and other trusted caretakers to provide a safe, loving, and supportive environment, and when that does not happen the long-term consequences can be devastating.

Borderline Personality Disorder and Changes in Brain Structure and Functioning


Careful medical examinations have revealed structural and functional anomalies in the brains of people diagnosed with borderline personality disorder. As a result of these deviations, BPD sufferers:

  • Have more intense emotional responses
  • Lose control of their emotions more frequently
  • Struggle to manage their anger
  • Lack empathy and often assume the worst about others
  • React with fear and paranoia in unfamiliar situations
  • Experience heightened levels of stress
  • Are prone to risky, impulsive actions

The changes in brain structure and functioning observed in BPD sufferers are caused by the interplay of genetic factors and environmental factors (life experiences) implicated in the development of borderline personality disorder. In other words, the brains of people with BPD are built differently and operate differently because genetic processes and traumatic life experiences affected their natural course of development.

In a sense, these alterations in the brain are borderline personality disorder, at least from a neurological standpoint. The differences in brain structure and functioning explain why BPD sufferers think, act, behave, and communicate the way they do, and if their brains were constructed differently they wouldn’t have been diagnosed with BPD. This is why BPD is now considered a brain disease and not just a psychological condition.

Borderline Personality Causes and the Implications for Treatment


Despite the changes in brain structure and functioning that accompany it, borderline personality disorder is still highly amenable to treatment.

For BPD sufferers, psychotherapy is an essential element of the recovery process, and that therapy must address their past trauma if it is to be effective. Mood stabilizers and antipsychotic medications may be prescribed to help individuals cope with their brain-based BPD symptoms, but recovery will remain elusive unless underlying issues that helped fertilize the growth of BPD are brought out into the open and discussed, honestly and sincerely, during trauma-focused therapy sessions.  

In many cases co-occurring disorders will also be present, and in all likelihood past trauma will be a contributing factor to those conditions as well.

No matter how difficult or painful things may have been, BPD sufferers should know there is reason for hope. One 2011 study reported that 85 percent of adults with BPD no longer met the criteria for the disorder 10 years after their initial diagnosis, and this number rose to 99 percent after 16 years in a separate 2012 study published in the American Journal of Psychiatry.

Borderline personality symptoms tend to reach their peak of intensity and frequency during young adulthood, when most people are diagnosed, and then decline in severity as a person ages. But that does not explain these statistics in their entirety. The effectiveness of BPD treatment is another reason for these encouraging numbers, and the sooner a person enters treatment after getting a BPD diagnosis the better their chances of recovery will be. This is especially true for those who begin their healing process in a fully-staffed residential treatment facility, where they can eliminate distractions and concentrate completely on their program of recovery.

Regardless of the causal factors responsible for the disorder’s development, people diagnosed with BPD have good treatment alternatives that can make a substantial and positive impact in their lives. Health and wellness are within their grasp, if they refuse to become discouraged and devote themselves fully to overcoming their illness.