Youth with traumatic brain injuries show higher levels of psychopathic traits, new study finds

A new study published in Research on Child and Adolescent Psychopathology has found that adolescent males in juvenile detention who have experienced a traumatic brain injury tend to exhibit higher levels of psychopathic traits than those without such injuries. The research also highlights that brain injury severity and number of injuries are linked to lower cognitive functioning and higher substance use—factors that, in turn, are associated with more pronounced psychopathic traits.

Traumatic brain injury, often caused by a blow or jolt to the head, can disrupt brain function. While symptoms vary, even mild injuries have been linked to long-term difficulties with thinking, emotion regulation, and behavior. In justice-involved populations, especially among adolescents, traumatic brain injury is common and has been associated with outcomes like substance use, aggression, and poor mental health.

Psychopathic traits, which include behaviors such as impulsivity, callousness, and manipulation, are also more common in youth who are incarcerated. These traits are often grouped into two domains: interpersonal and affective traits, like lack of empathy and shallow emotions (Factor 1), and lifestyle and antisocial traits, like impulsivity and criminal behavior (Factor 2). Because the teenage brain is still developing, especially in areas responsible for emotional regulation and impulse control, researchers believe that understanding how head injuries interact with these traits during this critical period is important for both treatment and prevention efforts.

The current study set out to examine how psychopathic traits are related to different aspects of traumatic brain injury—such as how severe the injury was, how many injuries a person sustained, and how early they began. The researchers also looked at whether these brain injuries are linked to psychopathy through their effects on intelligence and substance use, two known consequences of brain trauma.

The research team recruited 263 male adolescents, aged 14 to 21, from a maximum-security juvenile detention facility in New Mexico. More than half of the participants (54%) reported having experienced at least one traumatic brain injury. Some had suffered multiple injuries, and a small portion had experienced moderate to severe injuries.

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Each participant completed several assessments. These included a structured interview to measure psychopathic traits, tests to estimate intelligence, and evaluations for mood disorders and substance use. Traumatic brain injury history was assessed using a validated questionnaire that asked about symptoms, severity, and timing of injuries. The researchers used a statistical approach called structural equation modeling, which allowed them to examine both direct and indirect relationships among these variables, while accounting for measurement error.

Importantly, the study also tested whether the psychopathy measure worked equally well for participants with and without a history of brain injury. This step helped ensure that any differences observed between groups were not due to flaws or biases in how psychopathy was assessed.

The researchers confirmed that their measure of psychopathy was reliable and consistent across groups. This means that comparisons between youth with and without brain injuries were valid and not due to measurement issues.

Then, they looked at whether psychopathic traits differed between the groups. Adolescents with a history of traumatic brain injury scored higher on three of the four domains of psychopathy: affective traits (such as lack of remorse), lifestyle traits (such as impulsivity), and antisocial behavior (such as early conduct problems). There was no difference in interpersonal traits, such as superficial charm or manipulativeness.

Next, the researchers examined how specific characteristics of the injuries—like severity and number—were connected to intelligence, substance use, and psychopathic traits. They found that more severe injuries were linked to lower intelligence scores. In turn, lower intelligence was associated with higher levels of lifestyle and antisocial psychopathic traits. This suggests that brain injury may impair cognitive functioning, which then contributes to behavioral and emotional problems.

The number of brain injuries was also important. Youth with more head injuries were more likely to have used multiple substances. Higher levels of substance use were linked to both affective and behavioral psychopathic traits. This pattern indicates that repeated injuries may increase the risk of substance use, which may then relate to more severe psychopathic tendencies.

Altogether, the model used in the study accounted for a substantial portion of the variation in psychopathic traits, especially for those related to behavior and antisocial actions. The findings suggest that both intelligence and substance use may act as bridges linking traumatic brain injuries with psychopathic features in adolescents.

The researchers were cautious not to interpret their results as proving that brain injuries cause psychopathy. Because the data were collected at one point in time, the study cannot determine which came first. It’s possible that youth with higher levels of risk-taking or aggression are more likely to experience head injuries in the first place. Still, the findings align with past research showing that traumatic brain injury can negatively affect self-regulation and increase vulnerability to mental health problems.

The study suggests that when working with justice-involved youth, especially those with histories of head injury, it may be helpful to assess for cognitive deficits and substance use problems as part of routine care. Targeted interventions that support emotion regulation, improve cognitive skills, or address substance use may help reduce the expression of psychopathic traits. These findings also underscore the importance of early prevention strategies—such as head injury prevention and early mental health support—in helping at-risk youth avoid entering the justice system.

Future research would benefit from following youth over time to determine how brain injuries affect behavior and personality as they age. Including reports from parents or medical records could help confirm the timing and severity of brain injuries. And expanding this work to include girls and more diverse populations will offer a fuller picture of how these patterns might differ across groups.

The study, “Association Between Traumatic Brain Injury and Psychopathic Traits Among Justice‑Involved Adolescents,” was authored by Michaela M. Milillo, Craig S. Neumann, J. Michael Maurer, Christine Jin, Ella Commerce, Brooke L. Reynolds, Carla L. Harenski, and Kent A. Kiehl.