Do screens before bed lower kids’ melatonin?

What does melatonin actually do?

Mela is the body’s “night is coming” message. As evening gets darker, the body releases melatonin, a hormone it makes on its own, and that helps tell the whole system it’s time to wind down. In the crew, Corti helps wake the body in the morning and Mela puts it to bed.

Bright light in the evening turns Mela down, so sleepiness shows up later. That’s Glo’s trick. Glo is bright light late at night. This page is about the body’s own hormone. If you’re wondering about melatonin gummies, ask your pediatrician first.

What did the preschool study find?

Researchers studied 36 healthy preschoolers aged 3 to 4.9 years at home. On the final night, each child had an hour of light before their usual bedtime, at one of 15 brightness levels, and melatonin was compared with the evening before, spent in very dim light. Melatonin dropped by about 85% on average, with a range of 69 to 99%. Even the dimmest group, 5 to 40 lux, averaged about 78%. In 62% of the kids, melatonin was still below half its usual level 50 minutes after the light exposure ended.

Here is the surprising part: how bright the light was made little difference in these children. In adults, the response grows with brightness. Young kids appear to be more sensitive to evening light than we might assume.

Three honest limits. The study tested light in general, not screens. It was small. And a lower melatonin level is not the same as proven worse sleep. It supports “lower the lights in the last hour,” and it doesn’t prove what any one evening does to any one child.

Do screens count as evening light?

Screens put bright light close to the eyes, which is one reason pediatric guidance says to turn them off before bed. The American Academy of Pediatrics’ 2026 policy advises avoiding screen exposure for an hour before bedtime.

Light isn’t the only issue. Videos and games are built to keep going, so a tablet can hold a mind wide open even with the brightness turned down. Glo and Lupi often work as a team. That’s why “screens off about an hour before bed” is a rule about both light and attention.

How do I dim the evening without a battle?

Think “dim, warm, same.” You don’t need to sit in the dark. Lower and warmer is the usual advice.

• After dinner, switch off the bright overhead lights and use lamps.
• Screens go off about an hour before lights-out. Offer a swap, such as a bath, a book, an audio story or quiet drawing.
• Keep the same sequence every night so the body learns the cue.
• In the morning, open the curtains early or have breakfast near a window. Morning daylight is a helpful habit for setting the body clock, though not a guaranteed fix.
• Keep the plan on weekends too.

What about teens?

Teen body clocks already drift later during puberty, with melatonin timing shifting later. Add bright evening screens and the shift can feel even bigger. Aim for a “lights low” hour that the whole house shares, with phones charging outside the bedroom, and let your teen help design it.

What you’ll see at home

• Wired and chatty at bedtime after an evening of bright rooms or screens
• A long time to fall asleep, then hard to wake in the morning
• A second wind right when you want quiet
• Sleeping much later on weekends

Try tonight

1. After dinner, switch to lamps only. No overhead lights.
2. Turn screens off one hour before the usual bedtime. Offer a swap: an audio story, drawing or a bath.
3. Tomorrow morning, open the curtains first thing, or eat breakfast near a window.

Questions parents ask

Keep reading

• What does melatonin do? Your kid’s own night signal, explainedMelatonin is the hormone the body makes to say night is coming. How light affects it in kids, why teens run late, and habits that help sleep.
• Should kids sleep with their phone in the bedroom?Phones in kids’ bedrooms are linked to less sleep. Meet Bedi, the villain behind it, see what the research found and how to beat it tonight.
• How do I turn off autoplay, and why can’t my kid stop watching?Autoplay makes “one more” automatic. Here is what the AAP says, why kids struggle to stop, and how to turn autoplay off and end screens calmly.
• Why does my child get a second wind at bedtime?Yawning at 7, bouncing at 9:30. What a bedtime second wind may be, what Mela, light and the body clock have to do with it, and how to catch the window.
• Why can’t my child fall asleep at night?Lights out, brain on. Why kids lie awake, how Corti, Gabi and the body clock work, and calm habits to try tonight. Plus when to call the pediatrician.
• How much sleep does my child need? Hours by age, 4 months to 18AASM sleep hours for kids from 4 months to 18, signs your child is short on sleep, why teens run late, and how light, screens and bedtime change things.
• Cortisol for kids: the stress hormone explained (it’s not the villain)Cortisol is a useful alarm and a morning wake-up, not a villain. What it does in kids, when stress gets heavy, and how a calm grown-up helps.

Sources

1. Hartstein et al., 2022. High sensitivity of melatonin suppression response to evening light in preschool-aged children. Journal of Pineal Research.
2. American Academy of Pediatrics. Digital Ecosystems, Children, and Adolescents. Pediatrics, 2026.
3. Carskadon & Tarokh, 2014. Developmental changes in sleep biology and potential effects on adolescent behavior and caffeine use. Nutrition Reviews 72(Suppl 1).
4. Centers for Disease Control and Prevention. About sleep.