Good night, sleep tight, and don’t look into that tablet light.

Dads and moms who are concerned about the quantity and quality of their children’s sleep should keep mobile devices like phones, tablets and laptops out of kids’ bedrooms, according to a new study published Monday in JAMA Pediatrics.

It’s no surprise that using a mobile device before bedtime is associated with trouble falling asleep and staying asleep, as well as more daytime sleepiness. Most of us know that the light from tablets and phones can mess with circadian rhythms, making it harder for us and our kids to get a good night’s sleep, for example.

But the authors also report that simply having access to a device in the bedroom — even if it is not used before bed — is associated with increased odds of poor sleep length and quality for kids.

“Sleep is an often undervalued but important part of children’s development, with a regular lack of sleep causing a variety of health problems,” study leader Ben Carter from King’s College London said in a statement. “With the ever growing popularity of portable media devices and their use in schools as a replacement for textbooks, the problem of poor sleep among children is likely to get worse.”

Already, the researchers report, 72% of all kids and 89% of adolescents have at least one mobile device in the bedroom, and most of them regularly use it before bedtime.

For kids, a good night’s sleep is defined as falling asleep relatively easily, staying asleep throughout the night, and only waking up after nine or 10 hours of rest.

To read the rest of this article, click here: