Television watching is being linked to antisocial behavior in children.
Researchers at the University of Glasgow found that watching more then three hours per day significantly increased the risk of conduct and behavior problems.
The study looked at 11,000 children in Britain between the ages of five and seven.
It used questionnaires to ask parents about their child's adjustment and then about their television habits.
Two-thirds of the children watched television between one and three hours per day.
Fifteen percent watched television more than three hours per day.
Less than two percent watched no television.
Researchers found that computer games had no similar impact.
"[The study] suggests that a cautionary approach to the heavy use of screen entertainment in young children is justifiable in terms of potential effects on wellbeing, particularly conduct problems, in addition to effects on physical health and academic progress shown elsewhere," said the study authors.
The findings were published in the Archives of Disease in Childhood.