Vol. 11, No. 1, 2005 Page 5&7


A new study implicates temporal lobe abnormalities as a culprit in early-onset conduct disorder, which in turn is a strong risk factor for adult antisocial behavior.

Markus Kruesi and colleagues evaluated magnetic resonance imaging (MRI) scans performed in the early 1990s on 10 youths (ranging in age from 9 to 20) with early-onset, persistent conduct disorder and histories of attention deficit hyperactivity disorder. The researchers compared each subject to a control subject without any psychological disorder, matching the pairs for age, gender, and handedness.

Kruesi et al. report that "right temporal lobe and right temporal gray matter volumes were significantly reduced in subjects with conduct disorder compared with controls." Prefrontal volumes also were smaller than in controls, but this difference did not reach statistical significance. When the researchers controlled for the effects of substance abuse, the conduct-disordered subjects still showed significant reductions in right temporal gray matter volume.

The researchers say their findings are consistent with research indicating that lesions to the temporal lobes contribute to psychopathic or antisocial behavior. They cite one study of 18 violent adult offenders classified as psychopaths, which reported temporal lobe volume reductions of 20 percent. In addition, they note that low tonic heart rate, reduced electrodermal response to stimuli, and other signs of low arousal, which are frequently reported in antisocial adults, are also seen in patients with unilateral right temporal lesions. They note, too, that reduced empathy—a hallmark of antisocial or psychopathic behavior—is a common finding in frontotemporal dementia with pathology limited to the right temporal lobe.

Noting that other studies have reported significant reductions in frontal lobe volume, while their own study found only non- significant prefrontal reductions, Kruesi et al. say this may be a result of the older MRI scanning technique used in their own study or the confounding effects of drug use by subjects in other research.

While Kruesi et al.'s conduct-disordered subjects typically had lower IQs than controls, the researchers say that in two matched pairs, the conduct-disordered subjects had equal or higher IQs and still exhibited reduced right temporal volume. They say, "This is consistent with the possibility that the relatively smaller right temporal volume in those at high risk for antisocial personality may be independent of IQ." They note that the one female in their study did not exhibit temporal lobe volume reductions in comparison to the female control, and thus their findings may not extend to females.


"Reduced temporal lobe volume in early onset conduct disorder," Markus J. P. Kruesi, Manuel F. Casanova, Glenn Mannheim, and Adrienne Johnson-Bilder, Psychiatry Research: Neuroimaging, Vol. 132, 2004, 1-11. Address: Markus Kruesi, Dept. of Psychiatry and Behavioral Sciences, Medical University of South Carolina, 67 President Street, P.O. Box 250861, Charleston, SC 29425, kruesi@musc.edu.

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