NEW YORK — A gene previously linked to risk- taking and aggression appears to contribute to extreme violent behavior as well, according to a study that may open the way for treatments to prevent such behavior.
The gene, identified in an analysis of more than 700 criminal offenders, is one of two spotlighted in a study published Tuesday in the journal Molecular Psychiatry. The second gene is associated with attention deficit hyperactivity disorder, the authors wrote.
While researchers have attributed about 50 percent of severe antisocial or criminal behavior to genetics rather then environmental factors, they’ve identified only a few genes that may be involved. While the latest research won’t help predict which individuals might commit violence, it may lead to potential treatments, the researchers said.
“So far, nobody had found any gene associated with severe violent crime,” says Jari Tiihonen, a psychiatrist at Karolinska Institute in Stockholm, who led the study. “We wanted to try to find it, and we found two.”
Tiihonen and colleagues analyzed the genomes of 895 Finnish prisoners across the 19 largest prisons in Finland. The participants included nonviolent offenders involved in cases such as drunken driving and property theft, those convicted of violent crimes including murder, and extremely violent offenders, those responsible for at least 10 violent crimes.
The researchers compared the prisoner results with a control population of Finnish citizens. By doing so, they identified two gene variants present in those with extreme violent behavior, but not in those without.
The first is a mutated variant of monoamine oxidase A, or MAOA, which breaks down chemicals, such as dopamine and serotonin, that communicate information among brain cells. In 1993, MAOA was linked to impulsive aggression in five males from a single family and dubbed “the warrior gene” by the media.
The “warrior gene” finding has already begun to influence U.S. courts, yet there are strongly conflicting opinions about how much of a role the genetic basis of crime should play in the courtroom. It is too soon to know if this finding might also make its way into the justice system, but Tiihonen hopes it will not.
“No single risk factor, whether a gene variant or brain damage from a car accident or whatever, should affect a sentence,” Tiihonen said, adding that a person’s total mental capacity should be judged in assessing a sentence.
J.C. Barnes, a criminologist at the University of Cincinnati who wasn’t involved in the study, agrees. “Interactions between genes and the environment make it impossible to say this person will develop (violent behavior), just based on knowing a handful of genes, or even thousands of genes,” he says.
The second gene identified is a variant of cadherin 13, or CDH13, which makes a protein involved in the connections between neurons. CDH13 has been previously been associated with ADHD, which can involve a lack of impulse control.
The findings on the two genes also raise the possibility of screening children or others for a genetic disposition toward crime. Again, Tiihonen says it’s not possible with current knowledge. The genetic results are neither sensitive nor specific enough for screening purposes, he says.
Instead, the main importance of identifying these two gene associations is to illuminate biological mechanisms that may be involved in violent behavior for further study, he said.
