Hours spent watching TV or playing computer games may retard the psychological development of children, according to a study published in Pediatrics and reported by Agence France Presse.

For the study, researchers analyzed self-reported data from 1,103 children ages 10 to 11 about how much time they watched TV or played on the computer. (Time spent using the computer for homework didn’t count.)

Researchers also measured kids’ activity level by fitting them with a device called an accelerometer, which the children wore for seven days. In addition, the kids answered 25 questions about their psychological state. The higher the score, the more psychological difficulties the children experienced.

Scientists found that children who watched TV or engaged in computer play more than two hours each day were more likely to score higher than other kids who spent less time in front of the TV or computer.

In addition, researchers also found that even physically active kids who watched the same amount of TV risked increased psychological difficulties. (Previous study findings initially caused researchers to think that revving up physical activity could negate the bad effects of too much TV.)

Study authors wrote that many families believe that TV watching and computer play are part of a balanced lifestyle. But these study findings prompted researchers to advise parents to reconsider this theory.

Now scientists suggest parents limit their kids’ TV viewing and computer play to “ensure [children’s] optimal well-being.”

Did you know too much TV may also limit kids’ ability to focus? Click here to find out more.