People with borderline personality disorder may experience higher levels of immune system inflammation that relate to structural differences in the brain’s wiring. A recent small study found that individuals with the condition showed reduced integrity in specific brain networks alongside elevated inflammatory markers. Understanding this biological relationship could offer new ways to view the physical mechanisms behind emotional dysregulation. The research was published in the journal Psychoneuroendocrinology.
Borderline personality disorder is a psychiatric condition characterized by intense emotional instability, impulsivity, and difficulties in interpersonal relationships. Historically, psychological trauma was viewed as the primary origin of the condition. Researchers are increasingly investigating the underlying biological and neurological factors that might accompany these symptoms. The latest research looks beyond outward behavior to map the physical architecture of the central nervous system.
White matter is the brain’s internal communication network. It consists of long nerve fibers that connect different regions of the brain, allowing them to share information. Myelin, the protective coating around these fibers, acts like insulation on an electrical cable to keep neural signals moving efficiently. When the microscopic structure of white matter is altered, it can disrupt how different areas of the brain regulate emotions and process incoming information.
Simultaneously, researchers have observed that people with various psychiatric conditions often exhibit low-grade systemic inflammation. The immune system releases proteins called cytokines to signal inflammation throughout the body. There is growing interest in how these circulating inflammatory proteins might interact with the physical structure of the brain. Chronic immune activation is thought to influence how the brain develops and maintains its cellular architecture over time.
Piotr Podwalski, a researcher at Pomeranian Medical University in Poland, and his colleagues designed a study to explore these overlapping systems. They wanted to investigate whether people with borderline personality disorder showed measurable differences in white matter and immune markers compared to healthy individuals. They also sought to determine if higher levels of inflammation correspond to reduced white matter integrity in the patient group. Understanding these overlapping systems could eventually lead to new medical interventions that target the immune system to help manage psychological symptoms.
To conduct the small study, the research team recruited 40 women diagnosed with borderline personality disorder and 37 healthy women of similar ages. The researchers restricted the participant pool to females to reduce biological and clinical variations, as men and women often express symptoms of the disorder differently. The participants underwent clinical assessments and provided blood samples in the morning after fasting.
The researchers analyzed the blood samples for specific inflammatory biomarkers, including interleukin-6 and C-reactive protein. When the body encounters stress or infection, immune cells release interleukin-6, which then prompts the liver to produce C-reactive protein. Chronic elevation of these proteins indicates a persistent state of low-grade inflammation. This ongoing immune response can negatively impact healthy tissues, including the delicate architecture of the nervous system.
The researchers then used a specialized type of magnetic resonance imaging to scan the participants’ brains. This imaging technique tracks how water molecules diffuse through brain tissue. In an unrestricted environment, water molecules move randomly in all directions. Inside the brain’s white matter, water diffuses primarily along the length of the nerve fibers.
By tracking this directional movement, scientists can calculate a metric known as fractional anisotropy. Lower scores on this metric suggest that the microscopic organization of the nerve fibers has been disrupted or damaged. The researchers used this calculation to map out the integrity of major fiber bundles throughout the brain.
When comparing the two groups, the researchers initially found elevated levels of interleukin-6 and C-reactive protein in the participants with borderline personality disorder. The initial results indicated a heightened immune response in this clinical group. However, when the researchers adjusted their statistical models to account for body mass index and smoking habits, the differences in inflammation between the two groups were not statistically significant.
The brain imaging analysis revealed distinct structural differences regardless of lifestyle factors. The participants with borderline personality disorder displayed reduced white matter integrity in two specific pathways in the left hemisphere of the brain. These pathways are known as the superior longitudinal fasciculus and the superior thalamic radiation. Both of these neural pathways are highly active during complex cognitive tasks.
The superior longitudinal fasciculus is a long bundle of nerve fibers that connects the front of the brain to regions in the back. This specific pathway is heavily involved in language processing, memory, and the regulation of emotions. The superior thalamic radiation is another fiber bundle that links a deep brain relay center to the outer cortex. Disruptions in these pathways can impair the brain’s ability to filter sensory information and exert control over emotional responses.
The research team then combined the blood test data with the brain imaging results to look for specific relationships. They discovered an inverse correlation between the inflammatory markers and the structural integrity of the superior longitudinal fasciculus. Participants who had higher levels of circulating inflammation generally exhibited lower structural integrity in this specific brain network.
The research design relied on a single snapshot in time, which limits how the results can be interpreted. It is not possible to determine if elevated inflammation directly causes the observed alterations in brain structure. An alternative explanation is that structural brain differences and psychological distress trigger an inflammatory response in the body.
The study sample consisted entirely of women, meaning the results may not apply to men with borderline personality disorder. The two groups of participants also differed in their average body mass index, smoking habits, and years of education. While the researchers used statistical techniques to adjust for these variables, lifestyle factors are known to heavily influence both immune function and brain health over time.
Future investigations will need to track participants over several years to observe how inflammatory markers and brain structures change together. Tracking these biological measures across different developmental stages could map the sequence of events in the brain. Researchers may also incorporate more diverse groups of participants to see if these patterns hold true across the broader population.
The study, “Inflammatory biomarkers and white matter microstructure in borderline personality disorder: A cross-sectional study,” was authored by Piotr Podwalski, Bartosz Dawidowski, Kamil Lipiński, Łukasz Franczak, Patryk Wysocki, Marcin Jabłoński, Krzysztof Wietrzyński, Piotr Plichta, Ernest Tyburski, Łukasz Zwarzany, Andrea Amerio, Błażej Misiak, Wojciech Poncyljusz, and Jerzy Samochowiec.