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Brain Abnormalities and Violent Behavior

Abstract Introduction: It is difficult to rationally discuss the question of whether violent behaviour is a disorder because violent actions engender very strong emotional reactions in the public. But there are good reasons to believe that a variety of social and biological factors predispose the individual toward criminal behaviour. This study concerns the question, whether there is an association between violent behaviour and brain abnormalities. Method: Ninety-six mentally ill offenders of a high security prison consecutively underwent magnetic resonance imaging of the brain (MRI). The number of sex offenders was 62.5%. Fourteen offenders were excluded because they had a neurological disease, a psychotic disorder, a severe organic mental disorder or they were older than 60 years. All scan reports were in narrative format, and they were reviewed and coded according to presence or absence of brain abnormality. Neuroradiologists were blind to clinical diagnoses and offence history. Offenders were distributed either to a “high violent group” or to a “no or low violent group.” There was no significant difference in age between both groups. Results: In the included sample (n = 82; 50 sex offenders) 48.8% had MRI abnormalities. In the high violent group 65.5% showed MRI abnormalities. In the low violent group 16.6% had MRI abnormalities. This difference is significant (p = 0.001). The high violent sex offender group showed a MRI abnormality rate of 59.4%, and the low violent sex offender group 22.2%. The difference is significant (p = 0.011). There is no significant difference in MRI abnormality rate between the sex offender and the “non sex offender.” Conclusions: The results indicate that there is an association between unspecified brain anomalies and high violent behaviour in the whole sample as well as in the sex offender group. There is no association between sexual offence and unspecified brain abnormalities. Modern brain imaging techniques such as magnetic resonance imaging should be included in the diagnostic procedure of mentally ill offenders.