Boys who play video games on school days spend 30 percent less time reading, and girls spend 34 percent less time doing homework than those who do not play such games, U.S. researchers said Monday.
But they said video games do not appear to interfere significantly with time spent with family and friends.
"Gamers did spend less time reading and doing homework. But they didn't spend less time interacting with their parents or their friends, nor did they spend less time in sports or active leisure activities," said Hope Cummings of the University of Michigan, whose study appears in the Archives of Pediatrics & Adolescent Medicine.
The study comes as U.S. doctors voice growing concern about the long-term effects of video games.
Prior studies have linked prolonged gameplay with attention difficulties and poor academic performance. And some doctors have suggested the games interfere with social development and might be addictive.
Cummings and Elizabeth Vandewater at the University of Texas at Austin wanted to see how these games affect academic pursuits and social relationships.
They gathered data from a nationally representative sample of kids ages 10 to 19 in 2002. The kids tracked their activities on a random weekday and a random weekend day.
Of the 1,491 who participated, 534 adolescents, or about 36 percent, played video games. About 80 percent of them were boys.
The researchers found that boys spent an average of 58 minutes playing on weekdays, and an hour and 37 minutes playing on a weekend day. Of those sampled, girls spent an average of 44 minutes playing on a weekday and an hour and 4 minutes on a weekend day.
Cummings and colleagues found that video game use results in less time spent reading and doing homework, and that these trade-offs fall along gender lines.
"The reading was just for the boys. For the homework, it was just the girls," Cummings said in a telephone interview.
Gaming did not seem to affect time spent doing homework among boys or reading among girls, the study found.
Also, gamers did not spend less time with friends and parents.
"These findings do not support the notion that adolescents who play video games are socially isolated," the authors wrote.
They also said the findings indicate that gameplay can be a distraction from school-related activities, but that may not hurt grades.
"Although gamers spend less time reading and doing homework, there have been some studies that show that high academic achievers spend less time doing homework," Cummings said.
"Gamers may actually be more effective in completing homework assignments, and as a result, they spend less time doing homework. We need to look deeper into what is going on," she said.