Children who spend more than two hours a day at a computer or watching television are more likely than others to have psychological problems, scientists claim.
Researchers found that 11-year-olds who clocked up several hours in front of a screen each day scored worse on questionnaires designed to measure psychological health, regardless of how much physical exercise they got.
Angie Page, who led the study at the University of Bristol, said that as a precaution parents might consider limiting how long their children spend in front of a screen to no more than two hours a day.
The study of 1,013 children in the Bristol area found no evidence that sitting in front of a screen actually causes mental health problems. Alternatively, the findings might be a result of children with psychological difficulties, such as extreme shyness, being more likely to choose TV or computer games over more sociable activities.
"There's no evidence one way or the other and it could be either," Dr Page told the Guardian. But she added that some healthy children might be at greater risk of developing psychological problems if they increased their viewing time.
In the study, children were asked whether they agreed, disagreed or partially agreed with a list of statements, including, "I generally play alone or keep to myself" and, "I am often unhappy, downhearted or tearful". They then added details of how much exercise they took and how long they spent at a TV or computer screen. Their levels of exercise were verified by activity monitors worn on their belts for a week.
Writing in the journal Pediatrics, the team explain that while children who did little exercise fared well on the psychological assessments, those who filled their inactive time watching television or at a computer scored badly.