A recent study published in Psychiatry Research: Neuroimaging sheds light on the neural differences related to identity instability traits in borderline personality disorder. By analyzing brain patterns through a technique called Functional Near-Infrared Spectroscopy (fNIRS), the researchers found that individuals who struggle with identity instability exhibit more similar brain activity when judging their own traits and when imagining how others perceive them. This suggests that people with borderline personality traits may have difficulty distinguishing between themselves and others at a neural level.
Borderline personality disorder (BPD) is a mental health condition marked by unstable relationships, a fluctuating self-image, and impulsive behaviors. People with BPD often struggle with understanding themselves and others, and this can lead to misunderstandings, difficulties in relationships, and emotional instability.
Previous research has suggested that this condition might stem from an inability to accurately differentiate between one’s own thoughts and the perspectives of others. However, directly measuring this cognitive confusion has been challenging. The researchers wanted to explore whether these difficulties could be observed in the brain by examining the neural patterns of people with borderline personality traits when they were asked to judge both their own characteristics and those of others.
“We were interested in the neuroscientific mechanism of personality disorders,” said study author Seyul Kwak, an assistant professor of psychology at Pusan National University. “Despite numerous studies that have already highlighted interpersonal difficulties or emotional dysregulation typical of borderline personality disorder, we wondered what would be the core of such manifesting symptoms. We have applied psychoanalytic conceptions to neuroscience.”
The study involved 156 young adults, ranging from 19 to 36 years old, with an average age of 23. About 29% of the participants had a history of psychiatric treatment, and a smaller group was currently receiving treatment or taking medication. The researchers measured borderline personality traits using a well-established questionnaire, focusing on traits related to identity instability and impulsive behaviors.
The researchers used a brain imaging technique called fNIRS, which is non-invasive and measures brain activity by monitoring blood oxygen levels in the brain. Participants completed a task that required them to rate how well various personality traits applied to themselves and to others. These others included people they were close to, such as friends, and acquaintances with whom they interacted regularly but did not feel particularly close. In addition to these self-other comparisons, the participants also made judgments about word meanings in a non-social task, which served as a control.
The brain activity of participants was recorded while they performed these tasks, and the researchers analyzed how similar the brain’s responses were across different conditions—such as when participants judged themselves, when they thought about others, and when they tried to imagine how others perceived them.
The study’s findings were focused on the differences in how the brain processed information when participants thought about themselves versus others. In particular, the researchers found that the brain activity of individuals with higher borderline personality traits showed more similarity between self-judgment and third-person judgment (when they imagined how others perceived them). This neural similarity suggests that individuals with these traits may have difficulty mentally separating their own perspective from the perspectives of others, which could contribute to their sense of identity instability.
“We were particularly interested in the finding that neural differentiation in third-person inference—that is, imagining how a friend perceives you—was associated with borderline personality traits,” Kwak told PsyPost. “Rather than just forming a concept of themselves or their close friend, it may have been much more challenging for participants to distinguish between their own thoughts and how they believed their closest friend viewed them. It is important to note that your close friend’s model of you should be clearly delineated from how you think of yourself.”
Interestingly, the neural patterns of participants were different when they made judgments about people they didn’t feel close to, suggesting that the difficulty in separating self and others may be more pronounced in close, emotionally relevant relationships. These findings support the idea that people with borderline traits may conflate their own thoughts and emotions with those of others, especially when the other person is someone close to them.
“If one is struggling with emotional instability in their interpersonal relationships, and your relationships are sometimes too close and sometimes too aloof, you might be suffering from features of borderline personality traits,” Kwak said. “According to our findings, one might be having a blurry boundary between the concept of self and other, as observed with neural patterns. Either with psychological treatment or over the course of personal development, this boundary can become clearer and more stable.”
In contrast, impulsive behaviors, another key aspect of borderline personality disorder, were not predicted by the same neural patterns. This suggests that impulsive actions may be driven by different processes in the brain than those responsible for identity instability.
Although this study provides valuable insights, it has several limitations. First, the brain imaging technique used, fNIRS, provides less detailed information compared to other methods like functional MRI, so the results should be interpreted with caution. While fNIRS is effective at detecting overall patterns of brain activity, it may not capture all the intricacies of the neural processes involved.
Another limitation is that the researchers measured brain activity during specific task conditions, which may not fully capture how individuals with borderline traits behave in real-world social interactions. Future research could explore how these neural patterns relate to behavior in more naturalistic settings, such as everyday conversations and conflicts with loved ones.
“We inferred how one can differentiate the concept of self and other only at a neural level,” Kwak noted. “But this is highly indirect inference and further evidence should be supported with other behavioral or linguistic data.”
To build on these findings, future studies could examine whether the same patterns of neural confusion between self and others are observed in people with other types of personality disorders. It would also be beneficial to explore whether different therapeutic approaches, such as mindfulness-based therapies, can help people with borderline personality disorder develop a clearer sense of self and reduce the neural overlap between self and others.
“We hope to propose theoretically valid and clinically predictive neural markers of personality disorders,” Kwak said.
The study, “Borderline personality trait is associated with neural differentiation of self-other processing: A functional near-infrared spectroscopy study,” was authored by Do Yeon Yoo, Da Won Jeong, Min Kyoung Kim, and Seyul Kwak.
