Researchers have mapped how the physical structures of individual brains differ from a baseline norm in people who have a history of severe violence and schizophrenia. This analytical approach highlights individual differences rather than simple group averages, offering a potential path toward personalized psychiatric treatments. The findings were published in Translational Psychiatry.
Forensic psychiatry attempts to understand why some individuals with severe mental health conditions commit violent acts. Finding biological patterns in the brain can help doctors provide better care and improve clinical evaluations in high-security settings.
Previous brain imaging research has searched for structural abnormalities related to aggression. These older studies often grouped many patients together and compared their average brain structures to the averages of healthy people.
A statistical group average can easily hide the wide variety of differences that exist from person to person. Two individuals with the identical psychiatric diagnosis might exhibit completely different physical brain alterations.
Unn K. Haukvik, a researcher at the University of Oslo and the Centre for Research and Education in Forensic Psychiatry at Oslo University Hospital, led a team to approach this anatomical diversity differently. The researchers wanted to map the specific brain characteristics of single individuals instead of relying on a pooled statistical average.
To do this, the team used a statistical technique called normative modeling. This mathematical method works exactly like a pediatric growth chart in a doctor’s office.
Just as a pediatrician plots a child’s height against a massive database of typical growth trajectories, normative modeling maps a person’s brain anatomy against a vast reference population. This allows researchers to identify exactly how and where an individual’s brain deviates from the typical aging path.
The study involved adult men from the Oslo area. The researchers focused heavily on 38 men who had been diagnosed with a schizophrenia spectrum disorder and also had a documented hospital or court record of a severely violent episode.
Severe violence was defined strictly as homicide, attempted homicide, or physical or sexual violence directed toward another person. These specific participants were being held in high-security hospital wards as part of their mandated psychiatric care.
For comparison, the study included 138 men with a schizophrenia spectrum disorder but no history of violence. The study sample also included 20 men serving preventive detention sentences for severe violence who did not have a psychotic disorder.
A final group of 196 healthy men with no history of violence or severe mental illness served as a baseline control. The researchers only included male subjects because of the extreme scarcity of eligible women residing within the participating high-security units and prisons.
The researchers took magnetic resonance imaging scans of all the participants’ brains. Magnetic resonance imaging uses strong magnetic fields to create incredibly detailed, three-dimensional images of bodily tissues.
With these high-resolution images, the team measured three specific anatomical features. They looked at cortical thickness, which measures the depth of the brain’s wrinkled outer layer of tissue.
They also measured the total surface area of that outer layer, known as the cerebral cortex. Finally, they calculated the physical volume of deeper, subcortical brain structures beneath the outer surface.
The team then compared these individual structural measurements to a pre-existing normative model built from the brain scans of nearly 59,000 individuals from around the world. This massive reference set allowed them to pinpoint specific regions where a participant’s brain structure was either significantly larger or smaller than expected for their biological age.
The researchers found that the patterns of brain deviation were highly diverse across the participants. No single brain region was uniformly altered across all the individuals with a history of violence and psychosis.
Nearly 90 percent of the participants with both schizophrenia and a violent history had at least one extreme deviation in their brain structure. Overall, the clinical groups had a higher number of extreme negative deviations than the healthy participants did.
A negative deviation means that a specific brain region was unusually small or thin compared to the typical growth chart baseline. The men with both schizophrenia and a violent history showed extreme negative deviations most frequently in the basal temporal-occipital lobes.
The cerebral cortex is folded into a complex series of hills and valleys. A gyrus is one of the raised hills, while a sulcus is a shallow groove or valley dropping between them.
The differences in this violent group were clustered tightly around the collateral transverse sulcus and the lingual gyrus. These specific brain tissues are located near the bottom and back of the brain and are primarily involved in processing visual information.
Visual perception areas help people recognize physical objects and integrate visual memories. Alterations in these visual processing hubs have been linked in past studies to the formation of delusions, which are intensely held false beliefs that do not match reality.
This violent patient group also exhibited extreme negative deviations in the cortex of the cerebellum. The cerebellum is a densely packed structure at the base of the skull originally thought to only control physical movement.
Modern scientific research indicates that the cerebellum is also heavily involved in higher cognitive functions, social cognition, and executive control. Unusual physical variations in the cerebellum have been associated with aggressive behavior in other patient groups.
The pattern of brain differences in the violent schizophrenia group differed quite a bit from the other test cohorts. The men with schizophrenia who had no history of violence showed their most frequent deviations in the parieto-occipital area.
This parieto-occipital region sits higher up in the back of the head. It is known to be involved in spatial navigation and the coordination of hand and eye movements.
In contrast, the men who had committed violent acts but did not suffer from schizophrenia showed entirely different deviations. Their most frequent negative deviations occurred in the middle frontal areas of the brain, a region often associated with emotional regulation and inhibitory control.
The researchers also tested whether anatomical brain structures correlated with standardized measurements of psychopathy. Psychopathy involves a specific cluster of personality traits like a lack of empathy and a tendency toward antisocial behavior.
They found no statistically significant associations between psychopathy scores and the patterns of brain deviation. The data presented an extremely diverse array of anatomical differences that did not tightly map onto psychopathic trait severity.
The study has a few limitations that researchers must address in future investigations. The number of participants with a history of severe violence was relatively small, making it difficult to fully generalize the results to broader clinical populations.
The investigation was also cross-sectional, meaning it only captured a single diagnostic snapshot in time. A cross-sectional design cannot determine if these anatomical brain irregularities were present from early childhood or if they developed much later in life.
It is also difficult to entirely separate the physical effects of schizophrenia from external environmental factors. Cumulative exposure to required antipsychotic medications and past illicit substance use can both alter physical brain structures over time.
Future research should follow individuals longitudinally, tracking structural brain changes across many years. Observing how these deviations shift as people naturally age could clarify how the physical brain responds to psychiatric therapies.
Highlighting individual deviations instead of group averages offers a different way to understand the biological roots of severe mental health conditions. By focusing on personal anatomical differences, researchers hope to eventually provide clinicians with specific physical data that can better guide personalized psychiatric care.
The study, “Individual-level deviations from normative brain morphology in violence, psychosis, and psychopathy,” was authored by Unn K. Haukvik, Thomas Wolfers, Natalia Tesli, Christina Bell, Gabriela Hjell, Thomas Fischer-Vieler, Nina Bang, Ingrid Melle, Ole A. Andreassen, Kirsten Rasmussen, Ingrid Agartz, Lars T. Westlye, Christine Friestad, and Jaroslav Rokicki.
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