October 11, 2011 — The brains of violent offenders differ significantly from those with substance use disorders (SUDs), a finding that may aid in the development of more effective interventions for both conditions, new research suggests.
A small magnetic resonance imaging study of men in Germany found that those with SUDs showed lower grey matter volume in the prefrontal cortex (PFC) and poorer response inhibition scores compared with their counterparts without SUDs.
In contrast, violent offenders showed greater grey matter volume in the mesolimbic reward system compared with nonoffenders, but no differences in the PFC. In addition, violent offenders had higher scores for psychopathy and lifelong aggressive behavior.
"The number 1 takeaway message for clinicians is that volume reductions in the PFC may not be a sufficient condition for violent offending," lead author Boris Schiffer, PhD, MSc Psych, associate professor of forensic psychiatry at the University of Duisburg-Essen, Germany, told Medscape Medical News.
"Therefore, treatment approaches aimed at reducing the risk of violent offending should not only focus on improvement of behavioral control, which is associated with PFC function or dysfunction, but also on mechanisms associated with reward punishment computations — functions associated with the mesolimbic reward system," said Dr. Schiffer.
The study appears in the October issue of the Archives of General Psychiatry.
Costly Social Problem
"Violent criminal behavior causes much human suffering and is a costly social problem, accounting for 6.5% and 11.9% of the gross domestic product of Germany and the United States, respectively," write the researchers.
They note that previous research evaluating possible brain alterations for those with violent behavior have not taken into account whether or not study participants had a history of SUDs, which may be a possible cause of structural brain changes.
"The causes of violent behavior are still poorly understood, and therefore treatment approaches aimed at reducing violent offending and recidivism have revealed poor outcomes," added Dr. Schiffer.
The investigators recruited 51 men between the ages of 23 and 54 years from penitentiaries, forensics hospitals, psychiatric outpatient services, and communities in Germany.
Of these men, 12 were classified as having lifelong SUDs and exhibiting violent behavior (mean age, 36.4 years), 13 had SUDs only (mean age, 37.3 years), 12 were violent only (mean age, 37.4 years), and 14 were neither violent nor had an SUD (healthy control participants; mean age, 36.7 years).
Each of the violent offenders had been convicted of at least 3 crimes, with an average of 3.3 violent offenses.
All participants underwent structural magnetic resonance imaging at a university hospital. The Psychopathy Checklist-Screening Version was also used, along with assessments of aggressive behavior and impulsivity.
"Disentangling" Brain Correlates
Results showed that the groups with SUDs had significantly less grey matter volumes in their ventromedial prefrontal cortex, medial orbitofrontal cortex, and premotor cortex than the groups without SUDs.
Those who had SUDs only also showed a smaller total grey matter volume than the healthy control participants.
The groups that included violent offenders showed greater grey matter volumes in the left nucleus accumbens, bilateral amygdala, and right caudate head, and less volume in the left anterior insula, than the groups that did not have any offenders.
The violent offenders with SUDs also showed a greater total grey matter volume than those who were violent only.
Dr. Schiffer said that the volume increases in the mesolimbic reward system were "surprising," especially in the amygdala.
"Deficient amygdala function, in particular in emotion processing, and fear conditioning have been reported in a number of studies in violent offenders, especially those with psychopathy," he reported.
The investigators note that other findings from other studies indicating that violent offenders have reduced volumes in the orbitofrontal cortex, the ventromedial prefrontal cortex, and the premotor area compared with nonoffenders "may have failed to disentangle the structural brain correlates of persistent violence and SUDs."
They add that future studies will need "to link the observed structural abnormalities to specific deficits in functioning assessed by both neuropsychological tests and behavior in the real world and to the interactions of genes and environmental factors."
"I think this is an advance in understanding the structural brain changes associated with violent behavior; and because of the unique design, the investigators were able to disassociate it from [SUDs]," Warren K. Bickel, PhD, director of the Advanced Recovery Research Center at Virginia Tech Carilion Research Institute in Roanoke, told Medscape Medical News.
"Historically, that's been a challenge because often violent offenders also engage in substance abuse," said Dr. Bickel, who was not involved with this study.
He noted that there has been a concern in the field of addiction that substance abusers are violent.
"While that's certainly true for a portion of them, I think this clearly suggests that that can be disassociated, at least in the general public. Also importantly, it suggests future directions for understanding etiology between these 2 disorders and why there may be some degree of comorbidity between them."
However, Dr. Bickel noted that because this was a cross-sectional study, "strong inferences cannot be made about the developmental time course."
"Still, I think it does shed some light on the issues. And as more data come out, I think that will suggest novel approaches to treatment. For example, if I were to get violent offenders to use their amygdala less, would that help them control their behavior more? It brings up some interesting questions," he said.
"I think we're in a very exciting time and wouldn't be surprised if in a few years there aren't whole new approaches addressing challenges in brain function and structure and finding new ways to provide improvement."
The study was supported by the Landschaftsverband Rheinland. The study authors and Dr. Bickel have disclosed no relevant financial relationships.
Arch Gen Psychiatry. 2011;68:1039-1049. Abstract
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Cite this: Brains of Violent Offenders, Substance Abusers Differ - Medscape - Oct 11, 2011.