On average, preschoolers are watching screens for four hours a day, twice as much as recommended, the U.S. study says. ((CBC))

About two-thirds of U.S. preschoolers exceed the recommended daily amount of screen time from watching TV, DVDs, computers and video games, a new study suggests.

The Academy of Pediatrics recommends that parents limit screen time for preschoolers to two hours per day.

Researchers from the Seattle Children's Research Institute and the University of Washington looked at the daily screen time of nearly 9,000 preschool-age children as part of a study of more than 10,000 children born in 2001.

The researchers found 66 per cent of children studied exceeded the recommended daily amount.

On average, children were exposed to four hours of screen time each weekday, with 3.6 hours of the time at home.

Preschoolers in home-based child care had a combined average of 5.6 hours of screen time, with 87 per cent exceeding the guideline.

Those who went to child-care centres had an average of 3.2 hours each weekday at home and while at child care.

Among children who didn't go to child care, the average was 4.4 hours per day.

"Pediatric clinicians are uniquely positioned to encourage families to discuss screen time with their children’s caregivers and to advocate for high-quality child care," the study's authors concluded in Thursday's online issue of the Journal of Pediatrics.

"Efforts to decrease screen time in homes and home-based child care settings are needed."

Television viewing in young children has been linked to speech delays, aggressive behaviour and obesity.