A study of teenagers  published in the online journal BMJ Open, has revealed that they should aim to have a “screen-free” hour before bedtime.  This advice has come after new evidence suggested too much exposure to TVs, smartphones, tablets and computers can affect their sleeping patterns.

In a Norwegian study of 10,000 16 to 19-year-olds, researchers found that the longer a young person spent looking at an electronic screen before going to bed, the worse quality sleep they were likely to have.

Those who spent more than four hours a day looking at screens had a 49 per cent greater risk of taking longer than an hour to fall asleep and were three and a half times more likely to sleep for under five hours a night.

Excessive TV viewing and computer use have previously been linked to higher levels of depression and anxiety in children.

The researchers said that messaging friends online and watching TV may be simply replacing sleeping time, but may also be stimulate the nervous system or interfere with the body clock. They recommended health authorities update guidance on healthy use of electronic devices to take into account the increasingly common use of smartphones and tablets. 

This issue is becoming increasingly widespread as adults increasingly view their smartphone or tablet before bed also.