Recent research published in Psychiatric research: neuroimaging It has been suggested that people with borderline personality disorder show distinct structural differences in certain areas of their brains when they hear their voices. These physical brain differences tend to manifest in areas involved in language processing, sensory integration, and emotional regulation. This finding provides evidence that hallucinations may arise from biological mechanisms that are partially shared across different mental health conditions.
Borderline personality disorder (BPD) is a severe mental health condition characterized by profound difficulties with self-image, unstable relationships, and difficulty managing emotions. In addition to these well-known symptoms, up to half of people with this diagnosis also experience psychotic symptoms. Specifically, many of these patients experience auditory hallucinations. This means that you can hear voices that others cannot hear.
Historically, the scientific focus on auditory hallucinations has been on schizophrenia. Therefore, the physical brain features associated with voice hearing in borderline personality disorder remain poorly understood. Scientists wanted to see if certain brain structures differ between people with borderline personality disorder who hear voices and those who don’t.
“Auditory hallucinations refer to the experience of hearing voices in the absence of external auditory stimuli. Although most commonly associated with schizophrenia, these experiences can also occur in other psychiatric disorders, such as borderline personality disorder,” said study author Robert Christian Wolff, deputy director of the Department of General Psychiatry at Heidelberg University Hospital.
“Despite their relatively high prevalence in borderline personality disorder, the neurobiological basis of these experiences in this population remains largely unexplored. We wanted to address this gap by investigating whether the structural brain changes associated with hallucinations in schizophrenia also appear in borderline personality disorder. Understanding this may help reveal whether hallucinations reflect neural mechanisms common to a variety of psychiatric disorders.”
Researchers conducted a study using magnetic resonance imaging to examine the structure of the brain. They specifically measured the volume of gray matter, which refers to the dark tissue that contains the bodies of nerve cells involved in memory and language. The sample included 76 right-handed female participants and was selected to minimize the influence of gender-specific biological differences.
Study groups were divided into three specific categories based on clinical assessment. The sample consisted of 20 patients with borderline personality disorder who were currently or previously hearing voices. Also included were 26 patients with the same diagnosis who had never heard voices, and 30 healthy control participants with no history of psychiatric illness.
To measure clinical aspects, the researchers used a combination of interviews and self-report questionnaires. They validated psychiatric diagnoses using standardized clinical interviews designed for personality disorders. Specific characteristics of hallucinations, such as the psychological distress they cause, were measured using the Psychotic Symptom Rating Scale.
Participants then underwent brain scans using high-resolution magnetic resonance imaging equipment. The scanner captured detailed three-dimensional images of the brain’s anatomy. The scientists analyzed these images using special software and compared the amount of gray matter throughout the brain in all three groups.
When comparing all participants with borderline personality disorder to a healthy control group, the researchers found an overall reduction in gray matter volume. These reductions appeared in the frontal and parietal lobes, which help with motor and sensory processing. They also appeared in the cingulate cortex, an area associated with emotions, and the cerebellum, which regulates body movement and some cognitive functions.
Comparisons between the two patient groups revealed additional physical differences specific to hallucinatory symptoms. Patients who experienced auditory hallucinations had decreased gray matter volume in the occipital region of the brain compared to those who did not hear voices. The occipital lobe is located at the back of the brain and is traditionally associated with visual processing, but it also plays a role in integrating various sensory inputs.
“One notable finding was the involvement of occipital brain regions normally associated with visual processing,” Wolf told PsyPost. “Hallucinations are often studied primarily in relation to auditory- and language-related brain regions. The existence of structural differences in occipital regions suggests that broader sensory integration processes may also be involved. This supports the view that hallucinations arise from distributed brain networks rather than from a single brain region.”
The researchers also took a closer look at a brain region called the inferior frontal gyrus, which includes areas essential for speech production and language processing. They found that patients with borderline personality disorder who heard voices had decreased gray matter in this language center compared to healthy people. This suggests that there is a direct physical connection between the language network and the experience of hearing inner voices.
Finally, the researchers matched the hallucination patients’ brain scans with symptom severity scores. They found that higher distress and symptom severity correlated with lower gray matter volume in several key regions. These areas include the frontal lobe, parietal lobe, and cerebellum, as well as areas of the temporal lobe that process sound.
“Our findings suggest that the audio-auditory experience of people with borderline personality disorder is associated with structural differences in several brain regions involved in language processing, sensory integration, and emotional regulation,” Wolf explained. “Some of these patterns overlap with findings in schizophrenia, supporting the idea that hallucinations may arise from neural mechanisms that are partially shared across different diagnoses. At the same time, the results also indicate that these experiences are likely to result from complex interactions between cognitive, sensory, and emotional brain systems.”
“The structural differences we observed are subtle and occur at the group level. This means they cannot be used to diagnose individuals or determine whether someone experiences hallucinations. Instead, this discovery contributes to a better understanding of the brain networks that may be involved in these experiences. Therefore, the practical importance lies primarily in improving scientific knowledge about the mechanisms underlying hallucinations.”
“In the long term, this knowledge may help inform and refine treatment strategies, for example through the optimization of non-invasive neurostimulation approaches such as transcranial magnetic stimulation,” Wolf continued.
These findings show that the brain patterns of borderline personality disorder and schizophrenia overlap, but scientists cautioned against misinterpreting the results. It is important to remember that hallucinations in borderline personality disorder are not the same as hallucinations in schizophrenia. Factors such as exposure to severe trauma, high stress sensitivity, and severe emotion dysregulation may play a distinct role in how these sensory experiences manifest in borderline personality disorder.
This study also has some limitations that provide context for the results. This study used a cross-sectional design, meaning that only one snapshot in time was captured. Because of this, scientists are unable to determine how these brain structures change as the disorder progresses over the years.
“An important next step will be to investigate these processes over time and combine structural imaging and functional neuroimaging techniques to examine how brain networks interact during internal speech and related cognitive processes,” Wolf told PsyPost. “Longitudinal studies will also help reveal how hallucinations develop and change over the course of the disorder. In the long term, this study may contribute to more targeted treatment strategies that address the nervous systems involved in these experiences.”
“One important point is that hallucinations should be understood as transdiagnostic symptoms, meaning that they do not belong to a single diagnosis but can occur across a variety of mental health conditions. It is important to study such symptoms across diagnostic boundaries. This could lead to a more precise understanding of the underlying brain mechanisms and could help shift psychiatric research toward a more neurobiologically informed mechanistic perspective that focuses on functional domains and associated symptoms rather than traditional diagnostic categories.”
The study, “Structural correlates of auditory hallucinations in patients with borderline personality disorder,” was authored by Merct Koc, Marie-Luise Otte, Mike M. Schmitgen, Nadine D. Wolf, Yunus Balcik, Chantal Tech, Yéléna Le Prieult, and Robert C. Wolf.
