Does Your Kid Have Trouble Sleeping? Confiscate That Phone. The mere presence of a media device in the bedroom can be enough to distract from a good night's slumber.

Children using smartphones or tablets at bedtime are more than twice as likely to suffer from disrupted sleep than those without access to such devices.

A new study led by researchers from King's College London found that engagement with backlit screens within 90 minutes of slumber can disrupt sleep quantity and quality, and cause excessive daytime sleepiness.

"Our study provides further proof of the detrimental effect of media devices on both sleep duration and quality," Ben Carter, senior lecturer at King's College London, said in a statement.

Displays adversely affect sleep in various ways, including delaying or interrupting sleep time, psychologically stimulating the brain and affecting sleep cycles, physiology and alertness. But the mere presence of a media device in the bedroom can be enough to distract from a good night's sleep. The "always on" nature of social media and instant messaging, according to research, means kids are continuously engaged with their gadgets, even when not actively using them.

"Sleep is an often undervalued but important part of children's development, with a regular lack of sleep causing a variety of health problems," Carter said. "With the ever-growing popularity of portable media devices and their use in schools as a replacement for textbooks, the problem of poor sleep amongst children is likely to get worse."

Sleep disturbance in childhood is known to have negative effects on health: King's College London described consequences like poor diet, obesity, sedative behavior, reduced immune function and stunted growth, as well as links with mental health issues.

"Our findings suggest that an integrated approach involving parents, teachers and healthcare professionals is necessary to reduce access to these devices and encourage good sleeping habits near bedtime," Carter said.

Last month, the American Academy of Pediatrics released new guidelines to help families ensure their children aren't spending too much time in front of the TV or with their faces buried in a tablet. Infants younger than 18 months should avoid media altogether, while toddlers and pre-schoolers can enjoy one hour per day. Parents of children ages five to 18 should set consistent limits on time with and type of media they can consume.

Gadgets at bedtime can also affect adults, prompting mobile OS makers like Google and Apple to add "night modes" that dim the amount of blue light emitted by their gadgets.