New Insights Into the ‘Borderline Personality’ Brain

Borderline personality disorder is a mental health disorder characterized by symptoms that include mood instability, heightened impulsivity, and impaired self-awareness. Taken together, these symptoms can significantly diminish an affected individual’s capacity for fulfilling involvement in various aspects of his or her life. In the past, doctors and mental health researchers have had a fairly incomplete picture of the processes inside the brain that lead to the onset of borderline personality disorder. New information released in early 2013 helps clarify this picture by describing two of the disorder’s fundamental brain effects.

Borderline Personality Disorder Basics

Mental health professionals use the term personality disorder to describe any psychiatric/psychological condition that impairs an individual’s ability to understand or fruitfully participate in interpersonal relationships or social interactions, or to gain a stable picture of him- or herself apart from relationships with others. Generally speaking, the impairments underlying a personality disorder manifest as consistently recurring patterns of thought or behavior that go against the grain of social norms and create a sense of separation between the individual and his or her social/personal environment. The American Psychiatric Association, which creates the standard mental health guidelines used throughout the United States, recognizes borderline personality disorder and a number of other personality disorders as distinct categories of mental illness.

To qualify for a borderline personality disorder diagnosis, a person must have five or more symptoms specifically associated with the condition. Examples of these symptoms include angry outbursts that have no relevant social context, a destabilizing tendency to categorize relationships as strictly “good” or “bad,” unpredictable mood swings that include depressed states of mind, recurring involvement in various types of impulsive or reckless behavior, recurring expressions of boredom, the making of suicidal threats, and involvement in various forms of purposeful, non-fatal self injury. Some people with the disorder eventually kill themselves. While many people develop borderline personality symptoms during childhood or adolescence, current guidelines limit official diagnosis of the condition (or any other personality disorder) to adults, except in relatively rare circumstances.

Brain Function Basics

The brain’s primary processes are conducted through specialized nerve cells called neurons. With the help of chemicals known as neurotransmitters, these neurons carry on a constant, varying “conversation” that determines how the brain functions in any given set of circumstances. Although all neurons work on the same basic set of principles, specific types of neurons perform specific tasks in specific areas of the brain. In the context of borderline personality disorder, two especially important brain areas are structures called the limbic system and the frontal cortex. The activity level in certain neurons inside the limbic system helps determine a person’s basic emotional state, while the activity level in certain neurons inside the frontal cortex helps determine mood stability by regulating emotional fluctuations.

Changes Associated with BPD

In a study review published in early 2013 in the journal Biological Psychiatry, a team of researchers from the University of Toronto compiled information from 11 different studies that used modern brain imaging technology to examine the neuron changes that occur in people with borderline personality disorder. On the basis of this information, the researchers concluded that people with borderline personality disorder experience two distinct alterations in neuron function. First, the neurons in the limbic system that play a role in determining a person’s emotional state undergo heightened levels of activity that result in a markedly negative mood. In addition, the neurons in the frontal cortex that play a role in regulating mood fluctuations undergo a decrease in their normal level of activity. Without the limiting actions usually provided by the frontal cortex, negative moods generated in the limbic system grow abnormally persistent and intense.


Similar types of brain destabilization occur in people with other types of personality disorders, as well as in people with types of mental illness besides personality disorders. However, the authors of the study note, individuals with borderline personality disorder experience changes in a specific part of the frontal cortex—called the subgenual anterior cingulated—that appear to be a unique and identifying characteristic of the disorder. The authors of the study also note that, while people affected by borderline personality have turbulent emotional lives, the effects of the disorder can be controlled with forms of psychotherapy that improve the frontal cortex’s ability to regulate emotional fluctuations. The most successful existing therapies for borderline personality disorder already produce these improvements in significant ways.