There might be trouble brewing behind the glassy eyes of kids who spend too much time and energy on video games, Reuters reported after the release of a study.

In a two-year study of more than 3,000 schoolchildren in Singapore, researchers found that nearly one in 10 were video game “addicts,” and most were stuck with the problem.

Though these kids were more likely to have behavioral problems to begin with, excessive gaming appeared to cause additional mental woes, Reuters said.

“When children became addicted, their depression, anxiety and social phobias got worse, and their grades dropped,” said Douglas Gentile, who runs the Media Research Lab at Iowa State University in Ames and worked on the study. “When they stopped being addicted, their depression, anxiety and social phobias got better.”

Gentile said neither parents nor health-care providers are paying enough attention to video games’ effect on mental health.

“We tend to approach it as ‘just’ entertainment, or just a game, and forget that entertainment still affects us,” he told Reuters Health in an e-mail. “In fact, if it doesn’t affect us, we call it ‘boring!'”

But an independent expert said the study had important flaws. Click here to read the entire article.