Allowing children to have a smartphone or tablet in their bedroom could be playing havoc with their sleep – even if they don’t use it after turning the light out. A major scientific review has found that simply having an electronic gadget in the room leaves children ‘switched on’. Youngsters are restless because they anticipate receiving texts and social media messages from friends, which affects their night-time routine even if parents impose rules about ‘screen time’. The review 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 sleepy during the day. Experts from King’s College London and Cardiff University found that access to media devices at night, even without use, put children at 79 percent increased risk of getting insufficient sleep, 46 percent increased risk of poor quality sleep, and 127 percent increased risk of daytime drowsiness. Dr Ben Carter, who led the review, said having access to social media at all hours meant children were “always alert”. “If the first thing you do in the morning is check your phone and the last thing you do at night is check your phone, that is indicative of addiction behaviour,” Dr Carter said. “If that is the case, it is not surprising that you have poorer sleep quality. One theory is that continuous mental engagement with social media means they are always alert.” Dr Carter, who stressed that his theory had not been proven, added, “If you send a message an hour before you go to bed, you are still switched on when you try to sleep, in case there is a reply.” Separate research suggests that 72 percent of children and 89 percent of adolescents have at least one device in their bedrooms and most are used near bedtime. Dr Carter’s team, whose work is published in the JAMA Pediatrics journal, reviewed 20 existing studies from four continents, involving more than 125,000 children aged between six and 19. He said, “Our study provides further proof of the detrimental effect of media devices on both sleep duration and quality.” He said everyone should put their phones down 90 minutes before bedtime.