Study: MRI reveals brain differences for violent criminals
Structural MRI has revealed that individuals with violent criminal histories have larger gray matter volumes in the brain, while previous drug users show smaller volumes in other brain regions, compared with healthy individuals, firming up a growing link between biology and social behavior, according to a study published online June 6 in Archives of General Psychiatry.
In previous studies, researchers have discovered an association between brain morphology and the commission of violent crimes. However, because most persons with violent criminal records also present with substance use disorders, studies have failed to establish that structural brain differences are in fact linked to violent behavior. Instead, the differences might indicate that drug abuse holds the relationship with brain structure variations, argued Boris Schiffer, PhD, from the department of forensic psychiatry at the University Duisburg-Essen, in Essen, Germany, and colleagues.
The authors sought to test the relationship between violent criminal history and gray matter volume in various brain regions, while looking at the same phenomenon among individuals with substance use disorders.
Fifty-one men between the ages of 25 and 51 were included in the study. Twenty-four violent offenders (history of three or more violent criminal offenses), recruited from penitentiaries or forensic facilities, were divided into two groups: one consisted of 12 violent offenders without histories of substance use disorders and the other with histories of drug or alcohol abuse (excluding nicotine). A third group of 13 was recruited from substance misuse programs and a final group of 14 men without histories of either violence or drug abuse was included.
The authors also sought to correlate the behavioral histories and morphological differences with clinically assessed mental disorders, including psychopathy, aggressive behavior and impulsivity.
MRI showed that violent offenders had greater gray matter volumes than nonoffenders in mesolimbic areas, including the left nucleus accumbens, the bilateral amygdala and the right candate head. Violent offenders also presented with smaller gray matter volumes in the left anterior insula.
Meanwhile, substance use disorders were associated with smaller gray matter volumes in the ventromedial prefrontal cortex (PFC), orbitofrontal cortex (OFC) and the premotor cortex. Importantly, the relationships between violence and gray matter volume and substance abuse and gray matter volume were distinct from one another.
“Thus, the structural alterations associated specifically with persistent violent behavior may be increased [gray matter] volume in the mesolimbic region, whereas the structural alterations associated with [substance use disorders] are smaller [gray matter] volumes in the OFC, ventromedial PFC and premotor cortex,” Schiffer and colleagues noted.
Although these findings met the researchers’ hypotheses and confirm a number of previous studies, Schiffer and co-authors did note that earlier findings of reduced gray matter volumes in the OFC, ventromedial PFC and the premotor cortex among violent offenders may not have disentangled the independent effects of persistent violence and substance use disorders on brain structure.
The authors also observed positive associations between the volumes of the left amygdala and the left nucleus accumbens with psychopathy (Psychopathy Checklist–Screening Version, PCL-SV) scores.
Additionally, impulsivity served as a “primary” characteristic for distinguishing patients with substance use disorders, both self-reported attentional impulsivity and response inhibition. The relationship between impulsivity and gray matter volume mirrored that of substance use disorders—positive correlations between response inhibition scores and gray matter volumes of the medial OFC and the ventromedial PFC, “indicating that the smaller the volume, the more impaired the ability to withhold responses,” Schiffer and co-authors pointed out.
“Thus, the results from our study add to a growing body of evidence suggesting that structural abnormalities within the mesolimbic limbic reward system are associated with an early onset and stable pattern of antisocial behavior and the traits of psychopathy,” the authors continued.
Schiffer and colleagues emphasized that additional studies would be necessary to validate their findings, especially samples with detailed participant information. The present study did, however, control for age and IQ, both of which are known to affect brain structure.
“Structural alterations of the mesolimbic reward system were associated with violent behavior, high psychopathy scores and lifetime aggressive behavior, whereas reductions in [gray matter] volume in the medial OFC, lateral PFC and the premotor area were associated with substance use disorders,” the authors summed up.
“Our study illustrates the use of a strategy for disentangling the correlates of violent behavior from the correlates of substance use disorders, and if it can be replicated, it may be used in future studies aimed at furthering our understanding of brain mechanisms associated with these two conditions.”
In previous studies, researchers have discovered an association between brain morphology and the commission of violent crimes. However, because most persons with violent criminal records also present with substance use disorders, studies have failed to establish that structural brain differences are in fact linked to violent behavior. Instead, the differences might indicate that drug abuse holds the relationship with brain structure variations, argued Boris Schiffer, PhD, from the department of forensic psychiatry at the University Duisburg-Essen, in Essen, Germany, and colleagues.
The authors sought to test the relationship between violent criminal history and gray matter volume in various brain regions, while looking at the same phenomenon among individuals with substance use disorders.
Fifty-one men between the ages of 25 and 51 were included in the study. Twenty-four violent offenders (history of three or more violent criminal offenses), recruited from penitentiaries or forensic facilities, were divided into two groups: one consisted of 12 violent offenders without histories of substance use disorders and the other with histories of drug or alcohol abuse (excluding nicotine). A third group of 13 was recruited from substance misuse programs and a final group of 14 men without histories of either violence or drug abuse was included.
The authors also sought to correlate the behavioral histories and morphological differences with clinically assessed mental disorders, including psychopathy, aggressive behavior and impulsivity.
MRI showed that violent offenders had greater gray matter volumes than nonoffenders in mesolimbic areas, including the left nucleus accumbens, the bilateral amygdala and the right candate head. Violent offenders also presented with smaller gray matter volumes in the left anterior insula.
Meanwhile, substance use disorders were associated with smaller gray matter volumes in the ventromedial prefrontal cortex (PFC), orbitofrontal cortex (OFC) and the premotor cortex. Importantly, the relationships between violence and gray matter volume and substance abuse and gray matter volume were distinct from one another.
“Thus, the structural alterations associated specifically with persistent violent behavior may be increased [gray matter] volume in the mesolimbic region, whereas the structural alterations associated with [substance use disorders] are smaller [gray matter] volumes in the OFC, ventromedial PFC and premotor cortex,” Schiffer and colleagues noted.
Although these findings met the researchers’ hypotheses and confirm a number of previous studies, Schiffer and co-authors did note that earlier findings of reduced gray matter volumes in the OFC, ventromedial PFC and the premotor cortex among violent offenders may not have disentangled the independent effects of persistent violence and substance use disorders on brain structure.
The authors also observed positive associations between the volumes of the left amygdala and the left nucleus accumbens with psychopathy (Psychopathy Checklist–Screening Version, PCL-SV) scores.
Additionally, impulsivity served as a “primary” characteristic for distinguishing patients with substance use disorders, both self-reported attentional impulsivity and response inhibition. The relationship between impulsivity and gray matter volume mirrored that of substance use disorders—positive correlations between response inhibition scores and gray matter volumes of the medial OFC and the ventromedial PFC, “indicating that the smaller the volume, the more impaired the ability to withhold responses,” Schiffer and co-authors pointed out.
“Thus, the results from our study add to a growing body of evidence suggesting that structural abnormalities within the mesolimbic limbic reward system are associated with an early onset and stable pattern of antisocial behavior and the traits of psychopathy,” the authors continued.
Schiffer and colleagues emphasized that additional studies would be necessary to validate their findings, especially samples with detailed participant information. The present study did, however, control for age and IQ, both of which are known to affect brain structure.
“Structural alterations of the mesolimbic reward system were associated with violent behavior, high psychopathy scores and lifetime aggressive behavior, whereas reductions in [gray matter] volume in the medial OFC, lateral PFC and the premotor area were associated with substance use disorders,” the authors summed up.
“Our study illustrates the use of a strategy for disentangling the correlates of violent behavior from the correlates of substance use disorders, and if it can be replicated, it may be used in future studies aimed at furthering our understanding of brain mechanisms associated with these two conditions.”