Boys injured in only a couple schoolyard fights can suffer a loss in IQ that is roughly equal to missing an entire year of classes. For girls, even a single fighting-related injury can lead to such a loss of IQ.
 

Those are the key findings of new research by Florida State University medical investigators who noted even a few IQ points can lead to lower grades and occupational performance, mental disorders, behavioral problems, and even affect longevity.
 

"It's no surprise that being severely physically injured results in negative repercussions, but the extent to which such injuries affect intelligence was quite surprising," said Joseph A. Schwartz, a doctoral student who conducted the study with Kevin Beaver in FSU's College of Criminology and Criminal Justice.
 

Their findings, published in the Journal of Adolescent Health, are among the first to calculate the long-term effects of fighting during adolescence, a critical period of neurological development.
 

About 4 percent of high school students are injured as a result of a physical fight each year, the researchers said.
 

For the study, Schwartz and Beaver examined data from the National Longitudinal Study of Adolescent Health — collected between 1994 and 2002 — to see if serious fighting-related injuries resulted in significant decreases in IQ. In total, the researchers tracked the experiences of 20,000 middle and high school students into adulthood.
 

The results showed boys experienced a higher number of injuries from fighting than girls, but that the consequences for girls were more severe. The researchers also calculated that each fighting-related injury resulted in a loss of 1.62 IQ points for boys, while girls lost an average of 3.02 IQ points. Previous studies have suggested missing a single year of school is associated with a loss of 2 to 4 IQ points.
 

"We tend to focus on factors that may result in increases in intelligence over time, but examining the factors that result in decreases may be just as important," Schwartz said. "The first step in correcting a problem is understanding its underlying causes. By knowing that fighting-related injuries result in a significant decrease in intelligence, we can begin to develop programs and protocols aimed at effective intervention."