What Causes Borderline Personality Disorder?

What Causes BPD? Storm's Edge Therapy

There's no single cause of borderline personality disorder (BPD) and it’s a different combination of factors for each person. However, it is a disorder that has both strong genetic and environmental factors, with both being necessary in the majority of cases.


There is no evidence of a specific gene for BPD, but substantial research supports the hypotheses that your genes make you more vulnerable to developing BPD. People with the disorder have a very specific and definable brain profile, sometimes called “The Borderline Brain”, that underlines the ways in which they think and react.

This does not mean that you will definitely develop the full set of symptoms, it does however mean that you approach the world in a particular way. If your environment is supportive then you can develop adaptive and productive coping strategies as part of the normal developmental process.

Neuropsychology suggests that many of the experiences and struggles underlying this disorder come from dysfunctions of neurotransmitters in their brain, particularly serotonin. Altered levels of serotonin have been linked to depression, aggression and difficulty controlling destructive urges.

Magnetic resonance imaging (MRI) scans reveal that in many people with BPD, three parts of the brain were either smaller than expected or had unusual levels of activity. These parts were:

  • the amygdala – which plays an important role in regulating emotions, especially the more "negative" emotions, such as fear, aggression and anxiety
  • the hippocampus – which helps regulate behaviour and self-control
  • the orbitofrontal cortex – which is involved in planning and decision making

Put simply, people with BPD get upset very quickly and easily, calm down slowly and can’t use their 'thinking brain' well when distressed. In extreme cases individuals may experience dissociation, including memory gaps of what happened while they were upset. 

It is important to recognise that many symptoms are linked to your brain profile, and while the emotional part of your rain is activated, it can literally block rational thought - leading to an inability to engage with facts and logic while in this state. We help clients avoid this state, recognise it is occurring and understand how to manage these situations to limit their impact on your life.

What Causes BPD? Storm's Edge Therapy


Environmental Factors

The development of these parts of the brain is affected by your early upbringing. There are a number of common environmental factors:

  • being a victim of abuse; emotional, physical and/or sexual
  • ongoing exposure to fear or distress
  • childhood neglect, affecting normal development
  • a family member who had a serious mental health condition, such as bipolar disorder or an alcohol misuse problem

A person's relationship with their family determines what they believe about themselves, the world around them, other people and how relationships work. Children learn how to behave from the people around them, so growing up in a dysfunctional family they may learn some unhelpful ways of acting and feeling.

A way of understanding BPD is effective and extensive personality adaption to ongoing trauma, almost a trauma personality type. However, about 1 in 5 don’t experience any obvious trauma that is easy to point out. This is very invalidating as it leads to feeling terrible inside for no apparent reason and so you are not allowed to be hurt, angry or unhappy; 'you have nothing to complain about'. This actually can make treatment more difficult, because people don’t feel entitled to help, they behave recklessly to create external events that validate their inner feelings, there is less support and the issues are more complex to uncover. Nevertheless, the dysfunction and distress is as real and care is as deserving.

Unresolved fear, anger and distress from childhood can lead to a variety of distorted adult thinking patterns, such as: 

  • idealising others until they get close then demonising them unexpectedly
  • strong expectations of other people without evidence; for example expecting someone to care for you or abuse you when you only just met
  • feeling immature; believing that you're not an adult and your incompetence will be discovered showing you to be a liar
  • Thinking in very concrete ways and holding rigidly to your believes; i.e. she ignored my message therefore she hates me

While these may seem set, thinking patterns can be explored in sessions, and adapted through time and exploration of your interaction with others.

Our Borderline Personality Disorder Portal

The following pages are designed to provide additional information and advice on BPD treatment and our approach: