Rates of conduct disorder and violent crime have risen markedly among girls in recent years, according to both the U.S. Federal Bureau of Investigation and the U.K. Youth Justice Board.
“There are likely to be many reasons underlying this increase in the prevalence of conduct disorder in females,” Graeme Fairchild, Ph.D., a lecturer in psychology at the University of Southampton in England, told Psychiatric News, “such as increased alcohol or substance use,…shifts in societal expectations about girls’ behaviors, and the fact that most interventions for conduct disorder have been developed with boys in mind, thereby neglecting girls’ needs, which may be different.”
In new research reported by Fairchild and his colleagues in the January Journal of Child Psychology and Psychiatry, they suggested that “structural brain abnormalities exist in girls with conduct disorder” and may account for their behavior.
This study also found marked differences in brain structures between girls and boys.
Their subjects included 22 adolescent girls with a diagnosis of conduct disorder and 20 adolescent girls without it. Both groups were matched on age, IQ, and handedness. All subjects underwent structural magnetic resonance imaging of their brains.
The researchers found a reduction in certain areas of the brain in the conduct disorder subjects compared with the control subjects—reductions that might help explain certain behaviors exhibited by youth with conduct disorder. For example, the former group showed a smaller anterior insula on both sides of the brain and a smaller amygdala on the right side of the brain. The anterior insula is strongly implicated in empathy, which youth with conduct disorder are apt to lack. The amygdala is the brain’s fear hub, and youth with conduct disorder are known to act brazenly.
The investigators also compared the brain abnormalities in the 22 girls with conduct disorder with brain abnormalities that they had found previously in 22 boys with the disorder. The boys were matched with the girls on age, IQ, and handedness. The findings were similar, the researchers found. For instance, they found a reduced striatum in female adolescents with conduct disorder, just as they had in male adolescents with it. This brain region is involved in reward processing and the motivational aspects of behavior.
However, the study produced some surprises, Fairchild said. For example, they had expected to observe a smaller anterior insula in boys with conduct disorder than in boys without the disorder, just as they had found in girls with the disorder compared with girls without the disorder. Yet, in fact, they found that the anterior insula in boys with the disorder was larger than in boys without the disorder.
“Another surprise, at least for me, was the marked sex differences we observed in brain structure, irrespective of conduct disorder diagnosis,” Fairchild noted. “We found that girls showed much greater orbitofrontal cortex volumes than boys, while boys showed increased basal ganglia volumes relative to girls. These structural changes remained when controlling for overall brain volumes and might explain why boys are more reward seeking and prone to taking risks, whereas girls tend to be more reflective. Consequently [these differences] may account for the marked sex differences that are observed in aggressive and antisocial behavior even in general population samples.”
Fairchild said that based on the brain-related findings of his research, “it may be possible to use this information to develop neurofeedback-based interventions to enhance empathy in adolescents with conduct disorder.”
“There are significant forensic psychiatry implications of this study,” Jeffrey Metzner, M.D., associate director of the forensic fellowship program at the University of Colorado, Denver, told Psychiatric News.
The discovery by Fairchild and colleagues of brain abnormalities in girls with conduct disorder supports points made in an amicus brief submitted in 2004 by APA and other medical and mental health organizations in the U.S. Supreme Court case Roper v. Simmons, Metzner said.
The brief argued that adolescents who have committed serious crimes should not be eligible to receive the death penalty. One of the reasons stated in the amicus brief was that neuroimaging has shown that the adolescent brain continues to mature into early adulthood, and the regions associated with impulse control, regulation of emotions, risk assessment, and moral reasoning are the last to develop. Thus their reasoning ability should not be seen as equivalent to that of adults. Another reason given, Metzner stated, was that “adolescents who commit capital offenses suffer from serious psychological disturbances that substantially exacerbate the already existing vulnerabilities of youth.”
In 2005, the Supreme Court ruled in Roper v. Simmons that adolescents are not eligible for the death penalty for crimes committed under age 18 (Psychiatric News, April 1, 2005).
The study was funded by the United Kingdom Wellcome Trust and the United Kingdom Medical Research Council. ■