Safety and efficacy data surrounding such products are slim, while dietary supplements lack full regulation, warn the authors of the study in JAMA Pediatrics.
The figures are particularly concerning given that from 2012 to 2021, reports of melatonin ingestion to poison control centres increased by 530%, largely occurring among children under the age of five. More than 94% were unintentional and 85% were asymptomatic.
“We hope this paper raises awareness for parents and clinicians, and sounds the alarm for the scientific community,” said lead author Lauren Hartstein, a postdoctoral fellow in the Sleep and Development Lab at the University of Colorado Boulder.
“We are not saying that melatonin is necessarily harmful to children. But much more research needs to be done before we can state with confidence that it is safe for kids to be taking long term.”
Melatonin increasingly available over the counter in child-friendly formats
Melatonin, a hormone produced naturally in the pineal gland to regulate the body’s circadian rhythm and signal that it is time to sleep, is classified as a drug and available only by prescription in many countries.
In the US, however, chemically synthesised or animal-derived melatonin is available over the counter as a dietary supplement – and it is increasingly available in child-friendly gummy formats.
“All of a sudden, in 2022, we started noticing a lot of parents telling us that their healthy child was regularly taking melatonin,” said Hartstein, who studies how environmental cues, including light at night, impact children’s sleep quality and melatonin production.
During 2017-18, just 1.3% of U.S. parents reported giving their children melatonin. To get a sense of current prevalence, Hartstein and her colleagues surveyed about 1,000 parents in the first half of 2023.
They found that 18.5% of five- to nine-year-olds had been given melatonin in the previous 30 days; that number rose to 19.4% among 10- to 13-year-olds.
Nearly 6% of one- to four-year-olds had received melatonin in the previous month.
Preschoolers who were given melatonin had been taking it for a median length of a year. Primary-schoolers and preteens had used it for median lengths of 18 and 21 months, respectively.
The older the child, the greater the dosage, with preschoolers taking anywhere from 0.25 to 2 mg and preteens taking up to 10 mg.
Inconsistencies between melatonin content and label indications
In a JAMA study published earlier this year, researchers analysed 25 melatonin gummy products and found that 22 contained different quantities of melatonin than indicated on the label.
One contained more than three times the amount on the label; another had none at all. In addition, some melatonin supplements have been found to contain other concerning substances, such as serotonin.
“Parents may not actually know what they are giving to their children when administering these supplements,” said Hartstein.
Some scientists have also raised concerns that giving melatonin to young people, whose brains and bodies are still developing, could influence the timing of puberty onset. However, the few small-scale human studies to have explored this have yielded inconsistent results.
Melatonin can be useful as a short-term aid
Co-author Julie Boergers, a psychologist and paediatric sleep specialist at Rhode Island Hospital and the Alpert Medical School of Brown University, said that when used under the supervision of a healthcare provider, melatonin can be a useful short-term aid, particularly in young people with autism or severe sleep problems.
“But it is almost never a first-line treatment,” she said, adding that she often recommends that families look into behavioural changes first and use melatonin only temporarily. “Although it’s typically well tolerated, whenever we’re using any kind of medication or supplement in a young, developing body, we want to exercise caution.”
Anecdotally, she said she has heard from parents that the supplement often works well in the beginning but over time children may need higher doses to achieve the same effect.
Introducing melatonin early in life could also could send the message to children that, if you have trouble sleeping, a pill is the answer, said Hartstein.
The authors caution that the study was relatively small and does not necessarily represent usage nationwide.
However, Hartstein added: “If this many kids are taking melatonin, that suggests there are a lot of underlying sleep issues out there that need to be addressed. Addressing the symptom doesn’t necessarily address the cause.”