Is Borderline Personality Disorder Actually an Adaptation?

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Borderline personality disorder (BPD) is described as a disorder of interpersonal relationships. People with BPD traits often have unstable and chaotic relationships, where the sufferer can rapidly switch from valorizing the other person to devaluing them completely.

BPD is associated with mistrust, hypersensitivity to rejection, and difficulty controlling emotions. It’s also connected to impulsiveness and self-harm. BPD tends to have a positive outcome. Symptoms often gradually decrease around mid-life, and there are psychological treatments designed to help people diagnosed with BPD.

Mainstream research often presents BPD as the result of a brain dysfunction. One leading idea is that it is caused by a frontal lobe deficit, which impacts ordinary impulse control.

A very different picture has begun to emerge from the scientific literature, however. What if BPD is an adaptation, not a dysfunction? What if it’s a designed response to the problems of life, not a disease?

Seeing BPD as an Adaptation

The main proponent of the idea that some BPD traits may reflect an adaptation is Martin Brüne, professor of psychiatry at Ruhr University Bochum and a psychiatrist at LWL University Hospital.

Brüne has written on evolutionary psychiatry, which holds that we need to think about mental health and illness in terms of the big picture of the evolution of life on earth. Evolutionary psychiatrists often see adaptation in what would otherwise strike us as pathology, such as with depression.

Brüne’s (2016) account of BPD is based on the idea, originally set out by psychologist John Bowlby, that early in life children develop an “internal working model” of the world. This is a picture that tells them what the world is like and how to survive and thrive in it.

To some, the world is essentially a friendly and resource-plentiful place. Interpersonal relationships are durable, and they can expect their material and emotional needs to be met long into the future. Bowlby thinks children with stable attachments are likely to develop such a model.

To others, the world is a hostile, unpredictable place. Attachments are inherently fleeting and fragile, and there’s no guarantee that resources—either material or emotional—will be available in the near future. Bowlby thought that children who do not have stable early attachments, and, at an extreme, experience neglect, abuse, or other trauma, are more likely to form this second “picture” of the world.

Now, imagine how a child with this second “picture” of the world might think and act. They might mistrust others. Perhaps they’d be hypervigilant to signals of rejection and abandonment. With lower expectations about future provisions, this child might tend to have a more “all or nothing” approach to life, which an outside observer might call impulsive or dangerous.

In short, they might develop and display traits associated with the “borderline personality disorder” label.

Brüne does not think BPD is, in itself, an adaptation. He thinks it’s an extreme, and perhaps maladaptive, version of an adaptation. Still, whether we see BPD traits as an adaptation, or a maladaptive extreme of an adaptation, his view forces us to consider the potential value that those traits might have, or the value they might have had during a child’s formative years.

Evidence for the Adaptationist Model

There are several pieces of evidence that some BPD traits could be an adaptation, rather than a dysfunction (see Del Giudice, 2018 and Brüne, 2016). These include:

• BPD affects up to 6 percent of the general population and has genetic risk factors. As a rule, if a condition is widespread in humans and has a strong genetic risk factor, there’s a good chance it’s helping us in some way. Otherwise, natural selection would likely have eliminated it from the population.
• Neglect, abuse, and other trauma are risk factors for BPD. In fact, up to 80 percent of people diagnosed with BPD report such adverse childhood experiences.
• People diagnosed with BPD have a high level of emotional empathy—they can “read” others’ emotions well. This is what we’d expect on the assumption that BPD is an adaptation for navigating relationships and intimacy.

If BPD is an adaptation, then much of the language we use to describe it—brain defects, disorders, dysfunctions, diseases—are false and misleading. This is particularly troubling as such language can stigmatize people diagnosed with mental illnesses.

In contrast, recent evidence on depression, at least, suggests that when people see their depression as a coherent response to the problems of life, rather than a disease, they tend to feel more hopeful about a cure, more willing to see the positive side of their depression, and feel less stigma about telling other people about their struggles.

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Can the same be true of BPD? If so, that would inject a level of urgency into changing how we think and talk about it.

For more information and resources about BPD, see the podcast, Back from the Borderline, as well as psychologist Imi Lo’s website and psychologist Daniel Fox’s YouTube series.

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