British teens clock up six hours’ screen time a day at home, while North American children manage almost eight hours, and this poses major health risks, according to a leading psychologist.

According to research cited by Dr Sigman, negative impacts on health and wellbeing kick in after just two hours.  

In a new paper, published in Archives of Disease in Children, Dr Aric Sigman has warned that children and adolescents are viewing more media (TV, computer games and the internet) than ever before, and they are starting to use these media at ever younger ages.

He said that curbs on children’s daily screen time and delaying the age at which they start “the world’s favourite pastime” were urgently needed to minimise the risk of serious health and developmental problems.

Dr Sigman said 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.

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.  

He added that, by the age of seven, a child born today will have spent one full year of 24 hour days watching screen, rising to three full years by the time he or she is 18.  

Dr Sigman cites a litany of published studies showing links between the amount of time watching TV, playing computer games and time spent on the internet (collectively described as screen time) and ill health.

This includied increased risks of markers for heart disease, stroke, and diabetes. Such effects were not reversed by exercise, Dr Sigman said.  

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 psycho-social 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 three.

“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.”