Curbs on children's daily screen time and delaying the age at which they start "the world's favorite pastime" are urgently needed to stave off the risk of serious health and developmental problems, argues a leading psychologist and child health expert in the Archives of Disease in Childhood.
In the face of mounting evidence, doctors' leaders and government should take a stand and set clear guidelines on an activity that has so far eluded the scrutiny that other health issues attract, argues Dr Aric Sigman.
Children of all ages are watching more screen media than ever before, he says, and what is more, they are starting earlier and earlier.
Britain's children have regular access to an average of five different screens at home by the time they are 10 years old, in the form of TVs, games consoles, smart phones, laptops and tablets.
By the age of 7, a child born today will have spent one full year of 24 hour days watching screens, rising to three full days by the time s/he is 18, he says.
On average, British teens clock up six hours' screen time a day at home, while North American children manage almost eight hours, he says. Yet research suggests that the negative impacts on health and wellbeing kick in after just two hours.
Dr Sigman cites a litany of published studies showing links between prolonged screen time and ill health, including increased risks of markers for heart disease, stroke, and diabetes, as well as other biological effects associated with being sedentary that exercise does not seem to reverse.
Furthermore, viewing screen media is physiologically distinct from other forms of sedentary behaviour, with screen time increasingly considered an independent risk factor in its own right, he says.
Besides increasing the risk of obesity, prompted not only by inactivity, but also the disruption of food and hunger cues, prolonged screen time seems to reduce attention span because of its effects on the neurotransmitter dopamine.
Dopamine has a key role in the ability to pay attention, and is produced in response to "screen novelty," says Dr Sigman. It is also a key component of the brain's reward system and implicated in addictive behaviour.
"Screen 'addiction' is increasingly being used by physicians to describe the growing number of children engaging in screen activities in a dependent manner," he says.
And there are other psychosocial problems associated with excess screen time, including "Facebook depression," reported by the American Academy of Pediatrics; an increased risk of disengagement and vulnerability to victimisation after high levels of screen time in early childhood; poor social skills; and an impaired ability to express empathy.
"Perhaps because screen time is not a dangerous substance or a visibly risky activity, it has eluded the scrutiny that other health issues attract," he says.
Some countries have started to take the issue on board, notably the US, Canada, and Australia, he says. But he adds: "To date, views of the British and European medical establishments on increasingly high levels of child screen time remain conspicuous by their absence."
He lists a raft of often relatively simple measures that could make a difference, including limiting screen time and delaying screen viewing until the age of 3.
"Many questions remain regarding the precise nature of the association between screen time and adverse outcomes," he admits. But he concludes: "The advice from a growing number of both researchers and medical associations and government departments elsewhere is becoming unequivocal: reduce screen time."
More information: www.adc.com/lookup/doi/10.1136/archdischild-2012-302196