The researchers said the adverse effects are most apparent among teens that are diagnosed with a condition called disruptive behavior disorder or DBD. These kids, according to Dr. Vincent P. Mathews of the University of Indiana Medical School in Indianapolis, are the ones most likely to "act out by harming animals or property or fighting with other kids."
When he used a high tech scanning device called functional magnetic resonance imaging to track brain function in adolescents with DBD, he discovered "less activity in the frontal lobes." The frontal lobe is the area of the brain that controls emotions and impulses as well as attention span. Moreover when the DBD kids were exposed to violent video games, "there was even less activity," Mathews said.
He presented his findings at the 88th Scientific Sessions and Annual Meeting of the Radiological Society of North America.
The study suggests repeated exposure to the violent video games is "desensitizing the brain ... the result is that the child can no longer understand the real effect of violence," said Dr. Carol Rumach, professor of radiology and pediatrics at the University of Colorado School of Medicine in Denver, who was not involved in the study.
Mathews said he tested 19 teens that were diagnosed with DBD and compared their brain scans to 19 normal teens. Both groups were shown segments of a non-violent car chase video game and a violent James Bond spy video game while having their brains scanned by the MRI device. The device measures brain activity by increased blood flow in the scanned areas, said Mathews.
Even normal teens who said they frequently watched violent television and movies as well as regularly playing violent games had decreased activity when exposed to the violent video, Mathews said. Moreover, the brain changes were most apparent among "heavy users, meaning those who played for several hours every day," he said.
Mathews backed off from making any blanket statements about the danger of violent videos, but he said, "I think this information gives credence to what has become a growing concern about what is perceived as increased violence among adolescents."
With the holiday shopping just underway, video games -- and violent video games in particular -- are expected to be big sellers.
NPD Funworld, a trade publication that tracks the video game industry, reported last week the video game industry will post sales of more than $10 billion in 2002, and the fastest growing segment of the game market are games rated mature for violence. Mature video games are now responsible for 13 percent of sales, compared to 6 percent last year.
The market leader is the mature-rated video, "Grand Theft Auto 3," by Rockstar Games. It was rated the best selling video game of 2001 with U.S. sales already topping 4.2 million copies.