Almost half of American parents give their kids melatonin to help them sleep. Could it actually be doing the opposite?

A new study suggests that melatonin, the second-most popular supplement for kids after multivitamins, may reduce the time they spend in a critical phase of sleep that affects memory, learning, and emotional development.

Melatonin use has exploded over the last 20 years. While it’s thought of as a “natural” solution to get restless kids to bed, there’s growing concern about long-term use and side effects like nightmares.

Perhaps what’s most concerning is that because it’s a supplement and not tested for safety or efficacy by the FDA, the actual dose delivered to kids has been shown to be anywhere between only 74% to nearly 3.5 times the dose on the label.

“Melatonin is a hormone that our body naturally produces,” said Dr. Daniel Bigman, child adolescent psychiatry attending physician at Northwell’s Zucker Hillside Hospital and Cohen Children’s Medical Center. “So, whenever there is anything that we give to children that can alter hormones, that can cause a kind of a domino effect with things in our body.”

How melatonin might affect kids’ REM sleep

The new study looked at how 684 children slept with a polysomnogram, which looks at different stages of sleep.

“It looks at if our sleep is interrupted, how we breathe, and so forth,” Bigman said. “This study looked at the difference between children taking melatonin and those who do not.”

Researchers found that children who took melatonin had less rapid eye movement sleep, aka REM sleep, overall compared to kids who didn’t take the supplement.

“REM sleep is also thought of as the dream stage, or the dream sleep, because this is where most of us will experience dreams,” Bigman said.

More importantly, there’s evidence that this stage of sleep is crucial for memory, learning, and emotional development. Research indicates drugs like antidepressants and ADHD medication that affect REM sleep could hurt young brains’ development for this reason.

“While it’s hard to understand exactly the reason why, or if the melatonin was even the primary cause, I think what’s more important is that that there potentially is a relationship.”

Using melatonin

Melatonin is sometimes recommended for kids struggling with sleep — but Bigman notes “there should be caution because we don’t know everything about its effects.”

With limited FDA involvement in regulation of supplements like melatonin, “it is hard for us to know to quantify what it is that’s happening … as well as its long-term effects, because there isn’t robust data to truly understand how melatonin affects children’s brains, specifically in sleep.”

There’s also the question of whether kids getting melatonin actually need the pill or gummy. Things like iron deficiency, enlarged tonsils, and even nightmares could be keeping the child from a good nights rest. And melatonin won’t necessarily fix the problem.

Bigman says he’ll only recommend melatonin in the event a child is diagnosed to have a circadian rhythm or sleep-wake cycle disorder. This is when they’re staying awake long into the night and sleeping during the day.

“When we do prescribe melatonin, the doses are very small or where the times given are very strategically done. For example, sometimes we dose melatonin four, five, or six hours before the time we want them to sleep at a very, very low dose,” he explains.

“Giving a large amount of melatonin may not be beneficial just because we want someone or a child to sleep.”

Instead, the first line of defense should be sleep hygiene. That’s a consistent bedtime with a good routine that signals the body it’s time to wind down — like a bath or relaxing without a device. Screens should be put away 30 minutes to an hour before bed.

And kids should also have a sleep-friendly space to get some shut eye: somewhere quiet and dark. Bigman also suggests looking at physical activity, sugar, and junk food intake.

“All these things could potentially contribute to difficulty with sleep,” he said. Parents should shoot for their kids to get eight to 10 hours of sleep a night.