Well, DUH.
Childhood TV viewing linked to teen attention problems - New Scientist
Watching television more than two hours a day early in life can lead to attention problems later in adolescence, according to a large long-term study.The roughly 40% increase in attention problems among "heavy" TV viewers was observed in both boys and girls, and was independent of whether a diagnosis of attention deficit/hyperactivity disorder was made prior to adolescence.
"Those who watched more than two hours, and particularly those who watched more than three hours, of television per day during childhood had above-average symptoms of attention problems in adolescence," Erik Landhuis of the University of Otago in Dunedin, New Zealand, wrote in his report, published in Pediatrics on Tuesday.
Symptoms of attention problems included short attention span, poor concentration, and being easily distracted. The findings could not be explained by early-life attention difficulties, socio-economic factors, or intelligence, says the team.