Nature made melatonin first. Then supplement manufacturers created their own versions.

The National Institutes of Health says melatonin is a hormone the brain makes to help circadian rhythms and sleep line up. Light at night can cancel that natural production and mess with sleep cycles.

More than 6 million people in the United States take melatonin for sleep-related issues, according to an article in Everyday Health.

Melatonin likely does other things, too, though that’s not very well understood, NIH says.

That august body of medical research lauds melatonin for helping with jet lag, delayed sleep-wake phase disorder and anxiety before and after surgery, among others. But the agency’s less sanguine about some other supposed uses.

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NIH cites the American College of Physicians and the American Academy of Sleep Medicine in noting there’s not much evidence to support the idea that melatonin treats insomnia. More research needs to be done on the safety and effectiveness before it can be recommended for chronic insomnia.

Ditto helping shift workers adapt. It says the studies that have been done were small or inconclusive.

Research published in JAMA, the Journal of the American Medical Association, says though it is “generally regarded as safe, adverse effects have been reported, and data on long-term use and high-dose use are scarce.”

Earlier this year, Rebecca Robbins, who teaches sleep medicine at Harvard University, told CNN that “taking sleep aids has been linked in prospective studies with the development of dementia and early mortality.”

WebMd reports that melatonin use can be linked to headaches, dizziness, nausea, stomach cramps, drowsiness, confusion, crankiness, mild anxiety, depression, tremors and unusually low blood pressure.

What about safety? The overall view of safety for melatonin supplements isn’t clear if the product is taken at doses that exceed the body’s normal production, according to the National Institutes of Health.

The National Institutes of Health and others warn that:

  • Allergies are possible.
  • Interactions with other medicines are also possible.
  • There’s not enough research on use in pregnant or breastfeeding women.
  • People with dementia should not use it.

And to emphasize some of the contradictions in the literature regarding melatonin, consider this from the Mayo Clinic: “Research suggests that melatonin might reduce evening confusion and restlessness in people with Alzheimer’s disease, but it doesn’t seem to improve cognition.”

  • Because of little regulation of dietary supplements, the product quality and quantity may vary or not match the label.

A study by the American Academy of Sleep Medicine found “melatonin content did not meet within a 10% margin of the label claim in more than 715 of supplements, with the actual content ranging from 83% less to 478% more than the concentration declared on the label.”

  • Melatonin is contraindicated with some medical conditions.

Johns Hopkins University says not to use melatonin if you have an autoimmune disorder, a seizure disorder or depression, and to consult a doctor if you have diabetes or high blood pressure.

  • If it seems to be helping with sleep, it can probably safely be taken — at no more than a 5 milligram dose — for up to two months. Then stop, Johns Hopkins says.

The agency warns that while sales were up about 150% in 2020, compared to just four years before, so are poison control center reports in minors related to melatonin — to the point that there were 41,563 reports in 2021 about those younger than 19 taking melatonin. That group also accounted for hospitalizations and serious outcomes, including some who intentionally overdosed.

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Melatonin has not been shown to be addictive.

At normal doses, melatonin supplement is believed safe for short-term use in children. But again, the agency says there are not many studies. Nor is it clear whether taking the supplement will impact development.

The Mayo Clinic notes that melatonin can cause headache, dizziness, nausea and drowsiness. Less-common side effects include depression, mild tremor, mild anxiety, abdominal cramps, irritability, reduced alertness, confusion or disorientation.

And because of drowsiness, experts say not to drive or use machinery within five hours of taking melatonin.

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