smartphoneNine in 10 young people cannot sleep after being exposed to the blue light from their smartphones and tablets according to a survey, which suggests that near universal phone use is adversely affecting children’s health, mood, and performance at school.

Of 2,149 adults questioned, 78% said they used electronic devices before going to bed - this rose to 91% among the 18 to 24-year-olds questioned.

Professor Richard Wiseman of Hertfordshire University, who conducted the YouGov poll, said, “The blue light from these devices suppresses the production of the sleep-inducing hormone melatonin, so it's important to avoid them before bed time.”

According to The Sleep Council, many children and young people are seriously sleep deprived - one in three aged 12 to 16 sleeps for just four to seven hours a night, even though sleep experts say they should be getting eight to 10 hours’ a night.

Further reading: Children's online chat should be monitored says Conservative MP

In a separate Sleep Council poll of 1,000 young people, one in four fell asleep more than once a week while watching TV, listening to music or other technical distractions and 98.5% have a phone or TV in their room.

Dr Chris Idzikowski of the Edinburgh Sleep Centre says the impact of poor-quality sleep is similar to eating junk food regularly.

“We're seeing the emergence of junk sleep," he added. “That’s sleep that is neither the length nor quality that it should be in order to feed the brain with the rest it needs to perform properly at school.”

Those who do not get enough sleep are more likely to be overweight or obese because they crave sugary food for energy to stay awake during the day.

Sleep-deprived younger children are also likely to be overactive, seek constant stimulation and lack concentation.