Standards for gambling addiction were used to identify young video game addicts.
Most of them spent 24-hours a week glued to the screen -- about twice that of other players.
The Iowa State University study included children ages eight to 18.
Researchers say the U.S. is behind other tech-savvy countries in treating the addiction. South Korea has opened clinics to treat video game addiction.
The new study is in the may issue of "Psychological Science."