Borderline Personality Disorder Causes

What causes Borderline Personality Disorder? Unfortunately, there is no clearly known direct cause of BPD, although there are several main theories that are generally agreed upon by scientists.

Through a wide range of research over the past 90 years or so since the term ‘borderline’ was first mentioned in psychiatry, many scientists agree that the development of BPD involves a range of factors including the social and family environment, genetics and the brain.

It’s also widely believed that a childhood trauma plays a part in borderline personality disorder, as many patients report having suffered a traumatic event.

The Brain

Studies carried out on BPD patients, where they were given a range of brain scans include MRI, CT and PET, showed some abnormalities in  the areas of the brain which are responsible for emotions and stress response.

You can find out more about brain scans here:

These studies have shown that the amygdala (which is responsible for processing emotional responses) and the hippocampus (which is responsible for learning, emotions and memory) in the brain may be as much as 16% smaller in people with borderline personality disorder.


Borderline personality disorder appears to be more likely in families where there is a close relative with the same disorder. Close relatives include parents and siblings. In identical twins, studies showed there was a 2-in-3 chance of the other win having BPD. However, these theories remain theories as there is no evidence of a gene linked to BPD.


Trauma appears to play a large part – most people with borderline personality disorder have suffered a serious trauma in their lives, usually when they were young.

Traumas vary from person to person, as everyone reacts to a difficult situation differently, and what may be traumatic to one may not be to another. After the initial shock of a trauma, the response to the trauma may vary, but often the person has serious emotional reactions and that can impact on day to day life for some time after. Reactions to trauma may occur at the time or several years later.

Examples of traumas may include:

  • terrorist attacks;
  • war;
  • natural disasters;
  • sudden or unexpected death of a loved one – a child, partner/spouse, family member or friend;
  • rape or sexual assault;
  • serious medical illness;
  • difficult and/or life-threatening pregnancy;
  • domestic abuse and/or violence;
  • childhood neglect or parental abandonment;
  • childhood abuse;
  • victim of, or witness of, a serious crime;
  • a prison sentence;
  • divorce or other major life change.

Studies have shown that trauma during childhood/youth, when the brain is still growing and developing, alters the way the brain develops.

Borderline Personality Disorder is Complex

Studies cannot tell us how much – or in what way – genetics, brain development, trauma or life experience is responsible for borderline personality disorder. Borderline personality disorder is a complex condition that is yet to be fully understood.

However, thanks to the developments in psychiatry and psychology over recent years, borderline personality disorder is no longer the dark diagnosis it once was – there is now hope for patients to be able to recover, heal, manage their symptoms and live a full life.

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