Psychopathic traits linked to a thinner cerebral cortex in men

Higher levels of psychopathic personality traits mirror a reduction in the thickness of the outer layer of the brain across multiple regions. This structural relationship holds true in adult men regardless of whether they have a history of domestic violence or possess no criminal record at all. The findings were recently published in the scientific journal Aggression and Violent Behavior.

Psychopathy is a psychological condition characterized by a specific set of personality traits and behaviors. Individuals who score high in these traits often display a profound lack of empathy, a tendency to manipulate others, and a diminished capacity for feeling guilt or remorse. Psychologists typically divide the condition into two separate categories to better understand it.

The first category involves interpersonal and emotional features, such as superficial charm, grandiosity, and a failure to form deep emotional bonds. The second category features antisocial lifestyle behaviors, including high impulsivity, a need for stimulation, and a history of rule-breaking or delinquency. People with an abundance of these traits are at a higher risk of engaging in persistent anger and repeated violence.

Intimate partner violence is one such form of violence, involving physical, psychological, or sexual harm against a partner. Researchers are trying to map the biological foundations of psychopathy to better understand its connection to continuous aggressive behavior. While previous studies have looked at the brain structures of people with psychopathic traits, very few have specifically focused on men convicted of violence against their female partners.

Ángel Romero-Martínez, a researcher in the Department of Psychobiology at the University of Valencia, led a team to investigate how the physical anatomy of the brain correlates with these personality traits. The research team included colleagues from the University of Valencia and the La Fe Health Research Institute in Spain. They wanted to see if the physical structure of the brain associated with psychopathic traits differed between domestic violence perpetrators and non-violent men.

Before conducting their own experiment, Romero-Martínez and his colleagues completed a systematic review of the existing scientific literature. They analyzed 29 published studies to see which areas of the brain were most frequently linked to psychopathy in adult men. This initial phase allowed them to focus on regions that consistently showed physical differences, such as reduced volume or thinner layers of tissue.

The brain is covered by a folded outer layer known as the cerebral cortex, which is packed with the bodies of nerve cells, often called gray matter. The thickness of this gray matter varies across different regions of the brain and changes in response to aging, genetics, and environment. Variations in cortical thickness are associated with how well specific parts of the brain execute their functions, ranging from memory to impulse control.

The initial literature review pointed the researchers to specific frontal and temporal zones of the brain. The orbitofrontal cortex, a region situated just behind the eyes, appeared especially relevant because it helps integrate internal emotional signals and guides decision-making behavior. The insula, a region buried deep within the brain folds that aids in adopting other people’s perspectives, also surfaced repeatedly in the scientific literature.

Armed with these specific areas of interest, the researchers recruited 125 male participants for a physical brain scanning study. The sample included 67 men who had been convicted of intimate partner violence and were enrolled in a mandatory psychological intervention program. They also recruited 58 control participants from the surrounding community through advertisements and social media.

The researchers screened the control participants heavily to ensure they had no criminal records and no history of any form of intimate partner aggression. All participants in both groups were required to have no history of severe brain trauma, physical illnesses, or major psychiatric disorders outside the scope of the study. The men then took part in structured interviews to evaluate their psychopathic traits using an instrument known as the Psychopathy Checklist-Revised.

During these interviews, experienced specialists rated the men on the two main categories of psychopathy based on their answers and verified background information. Following the behavioral evaluation, the participants visited a hospital to undergo magnetic resonance imaging scans of their brains. The imaging machine used strong magnetic fields to create high-resolution, three-dimensional maps of each participant’s brain structure.

The researchers let automated software calculate the average thickness of the gray matter in the specific regions they had previously identified. They then ran mathematical models to see if there was a direct association between a participant’s score on the psychopathy checklist and the thickness of their brain regions. They factored in variables like age, educational level, head size, and drug or alcohol use to ensure these outside elements did not skew the results.

Across all 125 men, higher total scores in psychopathic traits mathematically correlated with a thinner cerebral cortex in several key areas. The left orbitofrontal cortex, the bilateral superior frontal gyrus, and the right dorsomedial prefrontal cortex all showed reduced thickness in men with higher traits. This pattern of reduced thickness was also present in the left insula and the right anterior cingulate cortex.

These inverse relationships were mostly driven by the first category of psychopathy, which deals with emotional detachment and interpersonal manipulation. The second category, which deals with antisocial lifestyle choices, only correlated with a thinner left superior frontal gyrus. Reduced tissue in these specific frontal and deep-brain regions could explain why individuals with high psychopathic traits struggle with emotional restraint, behavioral anticipation, and recognizing the feelings of others.

The researchers then tested whether being a convicted domestic violence perpetrator moderated this relationship between brain structure and personality traits. Including the participant’s group status in the statistical models did not significantly increase the amount of explained variance in the data. The biological relationship connecting high psychopathic traits to a thinner cortex was similar in the control group and the group of violent offenders. A non-violent man with an elevated psychopathy score exhibited the same structural brain profile as an offender with a similar score.

The authors noted several limitations regarding their study. Because the research took place at a single point in time, the results cannot prove that a thinner cortex directly causes psychopathic traits or violent behavior. The study also relied on a specific population of mostly Spanish men without severe mental health disorders, meaning the findings might not apply to women or other cultural groups.

Future initiatives should examine wider populations of people and incorporate technology that measures brain activity in real time, rather than just anatomical structure. This type of ongoing biology research helps psychologists build more accurate profiles of individuals prone to violent behavior. By combining neuroimaging results with standard psychological evaluations, professionals hope to eventually improve therapeutic interventions and lower the rates of domestic violence recidivism.

The study, “Reduced cortical thickness in fronto-temporo-parietal regions associated with high psychopathic traits: conclusions of a review and an empirical study with intimate partner violence perpetrators,” was authored by Ángel Romero-Martínez, María Beser-Robles, Leonor Cerdá-Alberich, Fernando Aparici, Luis Martí-Bonmatí, Carolina Sarrate-Costa, Marisol Lila, and Luis Moya-Albiol.