Vol. 6, No. 2, 2000 Page 6

Left hemisphere EEG abnormalities, violence linked

Focal abnormalities of the left brain hemisphere may be associated with violent criminal behavior, according to a study by German researchers.

Frank Pillmann and colleagues evaluated the EEGs of 222 criminal defendants referred for pretrial psychiatric assessment, comparing the EEG findings of violent and nonviolent criminals. One third of the subjects had abnormal EEG readings, and of these, 20 0 had focal abnormalities in the left or right hemisphere.

“There was no connection between the number of violent offenses and EEG abnormalities in general,” Pillmann et al. report. However, in subjects whose EEGs revealed left hemisphere focal abnormalities, the researchers noted “a significant excess of violent t recidivism.” Most of these abnormalities were detected in the temporal lobe. Focal abnormalities of either hemisphere were associated, in a substantial number of subjects, with brain trauma, retardation, or epilepsy.

Pillmann and colleagues say their findings are consistent with several other studies. Among them:

• M. Wong et al. found no association between generalized EEG abnormalities and violence in psychiatric patients in a forensic hospital, but did find a much higher incidence of focal abnormalities in a highly violent subgroup than in patients exhibiting g low levels of violence.
• A. Convit and colleagues found a correlation between left hemispheric slow waves and higher levels of violent behavior in violent psychiatric patients.
• N. D. Volkow and colleagues reported finding left temporal focal abnormalities in three of four subjects who exhibited repetitive, impulsive violence.