Children should not be given tablets or smartphones to play with until the age of two, a leading psychologist has warned. Picture: Wikimedia Commons

Children should not be given tablets or smartphones to play with until the age of two, a leading psychologist has warned.

And then they should have their daily "screen time" limited to an hour a day until they are at least five.

Dr Aric Sigman, a psychologist and lecturer in child health education, warned that staring at gadgets early in childhood can lead to "screen dependency disorder" – an addiction to electronic devices that may last a lifetime.

Writing in the Journal of the International Child Neurology Association, he cited evidence showing that high exposure to computers very early in life alters the structure of the brain.

Although for most children this is harmless, for those who are genetically predisposed to developing dependent habits it can create patterns that will stay with them for the rest of their life.

Scientists are not sure how many people are at risk, but Dr Sigman said parents and doctors should follow a "principle of precaution" and limit exposure.

People with screen dependency disorder become preoccupied, withdrawn, lie about how much time they spend on devices and even display withdrawal symptoms if they are unable to use them, he said.

"Most children will look at screens and will not become addicted, like most people who have a drink won’t become alcoholic," Dr Sigman said. "But for those who are genetically predisposed, early and high exposure over a number of years can set them up for dependency."

Dr Sigman said screen dependency is becoming "a rapidly emerging neurological public health issue" – but claimed it is unfashionable to talk about because people do not want to admit the dangers.

A milestone report published by Ofcom in November reported that average British three and four-year-olds use gadgets like tablet computers two hours a day – on top of watching television for another two hours. Older children aged five to 15 spend four hours using similar devices, and also watch TV for two hours.

Dr Sigman, who has taught NHS doctors and medical students, said: "We are setting up a generation in which a high number of people will have a problem.’ He said babies and toddlers are most at risk, but the chance of damage lasts into the late teens and even early 20s.

His review cites a 2016 study of 248 children aged five to 17, whose brains were repeatedly scanned over three years, which found significant changes to brain tissue density among children who played video games for long periods.

Dr Sigman said: "People are unaware of this huge body of evidence about this – screen behaviour is not a social issue, it is not a cultural issue, it is a medical issue."

He advised parents to follow the guidance set by the Australian Government which says those below the age of two should not be exposed to screens at all.

Britain does not have guidelines on the issue, although Dame Sally Davies, England’s chief medical officer, urged parents to set their own "age-specific maximum times" to reduce potential damage.

Dr Ben Carter, a scientist at King’s College London, advises everyone put their phones down an hour and a half before bedtime. He found that children and teenagers who use an electronic device within 90 minutes of going to bed are twice as likely to get insufficient sleep, and nearly three times as likely to feel tired during the following day.