It is generally accepted that pathological violence is a combination of factors, both biological and psychological, but brain studies of violent criminals haven't revealed much.

However, a new brain imaging study suggests that men with a history of violent behavior may have greater gray matter volume in certain brain areas, whereas men with a history of substance use disorders may have reduced gray matter volume in other brain areas.

The researchers compared violent offenders, both with substance use disorders (SUDs)(12) and without(12), along with nonviolent men, both with (13) and without SUDs (14). The first group was recruited from penitentiaries and forensic hospitals, and the second group was recruited from psychiatric outpatient programs and by advertisements and employment agencies. Experienced psychiatrists assessed the participants—males between 23 and 54 years—for mental disorders, psychopathy, aggressive behavior and impulsivity. All study participants underwent structural magnetic resonance imaging at a university hospital.

The researchers identified differences in the brains of men in the various categories. Participants with a history of violence and had a greater volume of gray matter in certain brain areas than nonviolent participants, regardless of a history of SUDs. The increases in gray matter volume among violent offenders appeared in the mesolimbic areas of the brain, which previous research suggests are linked to feelings of desire and reward as well as antisocial behavior and psychopathology. Further, gray matter decreases in other areas of the brain characterized men with SUDs regardless of a history of violence.

The larger gray matter volumes in participants with violent tendencies were associated with higher scores for psychopathy and lifelong aggressiveness, whereas the smaller volumes of gray matter in those with SUDs appeared to be related to response inhibition. Among men with SUDs, the study found smaller gray matter volume in areas of the brain that play a part in social behavior as well inhibition. The authors call for more research "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."

Citation: Boris Schiffer; Bernhard W. Müller; Norbert Scherbaum; Sheilagh Hodgins; Michael Forsting; Jens Wiltfang; Elke R. Gizewski; Norbert Leygraf, 'Disentangling Structural Brain Alterations Associated With Violent Behavior From Those Associated With Substance Use Disorders', Arch Gen Psychiatry, Jun 2011; doi:10.1001/archgenpsychiatry.2011.61