Adolescent boys hurt in just two physical fights suffer a loss in IQ that is roughly equivalent to missing an entire year of school, according to a new study.
The research from Florida State University also found that girls experience a similar loss of IQ after just one fighting-related injury.
“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, Ph.D., in FSU’s College of Criminology and Criminal Justice.
The findings are significant, according to the researchers, because decreases in IQ are associated with lower educational achievement and occupational performance, mental disorders, behavioral problems and even longevity.
About four percent of high school students are injured as a result of a physical fight each year, the researchers noted.
For the study, they used data from the National Longitudinal Study of Adolescent Health collected between 1994 and 2002. The national study began with a nationally representative sample of 20,000 middle and high school students who were tracked into adulthood. Each time data was collected, the students were asked about a wide variety of topics, including personality traits, social relationships and the frequency of specific behaviors.
For their study, the researchers examined whether serious fighting-related injuries resulted in significant decreases in IQ over a five- to six-year time span.
Not surprisingly, boys experienced a higher number of injuries from fighting than girls, according to the study’s findings.
However, the consequences for girls were more severe, a fact the researchers attributed to physiological differences that give males an increased ability to withstand physical trauma.
The researchers found 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 shown that missing a year of school is associated with a loss of 2 to 4 IQ points.
The impact on IQ may be even greater when considering only head injuries, according to the researchers. The data they studied took into account all fighting-related physical injuries.
The findings highlight the importance of schools and communities developing policies aimed at limiting injuries suffered during adolescence, whether through fighting, bullying or contact sports, Schwartz said.
“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,” he 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.”