Why Young Teens Should Never Go to Bed With Their Phones On

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Puberty does bizarre things to kids’ bodies, like making them more vulnerable to the sleep-busting effects of screen light. (Photo: monkeybusinessimages/iStock)

Want your tween or young teen to rise and shine on school mornings — not head to homeroom in a groggy haze? Make sure she turns off her phone or tablet at least a half-hour before hitting the sheets the night before.

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A new study from Brown University found that kids between ages 9 and 15 were especially sensitive to exposure to light during the evening hours, even the low levels of light emitted by an electronic device.

The more evening light exposure kids in this age group racked up, the lower their levels of the sleep hormone melatonin were — and the less rest they were able to score, according to the study, published on August 26 in the Journal of Clinical Endocrinology and Metabolism.

“Melatonin suppression pushes their body clocks to a later time, and that makes it harder to get up in the morning,” senior study author Mary Carskadon, professor of psychiatry and human behavior at the Warren Alpert Medical School of Brown University, tells Yahoo Parenting.

Researchers (and parents, too) have long known that as kids enter puberty, they tend to stay up later — to text friends, watch Pretty Little Liars, or just have some time independent of other family members. What experts weren’t sure of is how much of a role adolescent biology plays in this body clock shift.

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So Carskadon and her team devised a study. They looked at 38 kids in early adolescence (ages 9 to 15) and compared them to 29 kids well into puberty (ages 11 to 16). They exposed each group to different levels of light in the morning and evening, then measured their melatonin levels.

The results showed that biology has a significant influence. The first group demonstrated suppressed melatonin levels after being exposed to low levels of evening light, while the melatonin levels of the older study subjects were not as affected.

“This biological force driving younger teens to stay up later collides with the reality that they also have to get up early in the morning to go to school,” says Carskadon. “In a perfect world, they wouldn’t have to get up so early, but they do.” The less sleep they get, the more it affects their reading ability, memory, and overall ability to learn, she adds.

What’s the takeaway for parents? While all kids should be encouraged to shut off their devices before bedtime, it’s especially critical for those in their middle school and early high school years, who are biologically more vulnerable to the effects of light on melatonin, says Carskadon.

She suggests that parents set limits so that phones, tablets, computers, and TVs are turned off at least 30 minutes before bedtime and that parents prohibit any light-emitting gadget in a child’s room, so kids can’t sneak them under the covers and use them past bedtime.

“Minimize evening light and then maximize it in the morning,” she says. Morning light cues the body clock to awaken, so bright light on school mornings will make tweens and teens more energized and alert and better prepared to start the school day.

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