November 26, 2008
Aggression research may lead to early intervention
CARBONDALE, Ill. -- A common genetic mutation might help predict which boys with intellectual disabilities will cause trouble in school.
The mutation results in an oversupply of a brain chemical tied to aggression. Previous research by an international team of scientists has linked it with violent or antisocial acts committed by New Zealand men who suffered mistreatment in their early years.
Now researchers from Southern Illinois University Carbondale and Vanderbilt University have found a connection between that mutation and problem behavior in a group of men with intellectual disabilities. Men in the study who had the mutation were more than twice as likely to lash out, destroy things or hurt themselves than were their counterparts who did not have the mutation.
“This study was not designed to label people (as aggressive) from an early age,” said Michael E. May, project leader and an assistant professor of special education at SIUC.
“Ultimately, we want to identify these kids so we can develop successful early intervention strategies for them, to arrange their environment in such a way that we can teach them to get what they need in a more appropriate way.”
Roughly a third of the general population has this mutation, but the research done with New Zealanders suggested environmental factors — maternal rejection, inconsistent care and physical or sexual abuse — provide the needed trigger for the accompanying aggression.
“We decided to look at adults because most of them have been in situations that can produce environmental triggers,” May said.
“We chose individuals from institutional and community settings where environmental triggers were equally likely to take place,” he added.
Other researchers have associated this mutation with the more severe forms of autism, which is often accompanied by a degree of mental retardation. This led the team to focus on adults with mental retardation.
The 105 men studied ranged in age from 18 to 50 and live in Southern Illinois or Middle Tennessee. Matched by age and IQ, two-thirds had intellectual disabilities; half of these had lengthy histories of trouble making. The others came from the general population and no reported behavior problems. The study involved only men because the gene in question resides on the X chromosome. Men have just one such chromosome while women have two.
“It is more efficient in terms of time and resources to search one X chromosome, and males are more likely to act out than females are,” May said.
Researchers collected DNA from the participants, had it checked for the mutation and then compared results with behavior reports assembled by trained agency staff. They found that 43 percent of the men with both mental retardation and problem behavior had the mutation, while just 20 percent of the other men did.
Although this study reinforces other research linking aggression with this particular genetic variant, the fact that the mutation appears in men who do not behave badly also underscores that genes are not destiny.
“It is important to emphasize that when we look to identify the cause of aggressive behavior, we’re not just looking at genetics,” May said.
“It’s not ‘nature versus nurture’ -- they influence each other.”