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Is Melatonin Safe? Should You Stop Taking It?

Go to the supplement aisle of almost any store in the US and you'll find melatonin, a synthetic hormone, marketed as an effective natural sleep aid, even for children! But is melatonin actually safe to use? Studies say ...

By
Sabrina Stierwalt, PhD
5-minute read
Episode #393
The Quick And Dirty

Clinical results on the efficacy of melatonin are still inconclusive although anecdotal evidence for its use as a sleep aid is strong. The supplements are not well regulated in the United States meaning you might not know exactly what you're taking.

The popularity of melatonin, a supplement used by many as a sleep aid, is quickly growing. The synthetic hormone is often taken to help combat insomnia, trouble falling asleep due to anxiety, and jet lag due to travel or shift work. In 2012, more than 3 million people in the United States reported taking melatonin and in 2019 the global market for the supplement was estimated somewhere around $1 billion annually

More and more parents and caregivers are giving melatonin to their children. Melatonin is one of the most popular natural products given to children, second only to fish oil. We often equate "natural" with "safe," but just because something is naturally occurring doesn’t mean it can’t have any adverse effects.

As the popularity of melatonin grows, so do the concerns over whether or not we should be relying on it so much, especially when it comes to our kids.

Is melatonin effective?

The anecdotal evidence for melatonin as an effective sleep aid is strong. Ask any mom group and you’ll find a significant fraction who swear by it, both for themselves and for their kids.

But evidence at the clinical level is so far less conclusive. For example, the authors of one literature-based review found that taking melatonin helped shift workers sleep longer during the day by an average of 24 minutes. But they also found those taking a placebo drug saw similar benefits. 

The anecdotal evidence for melatonin as an effective sleep aid is strong, but so far, the clinical evidence is less conclusive.

In another meta-analysis that combined 19 studies involving over 1,600 participants, the authors found a statistically significant result that taking melatonin increased a person’s total sleep time … but for a total of just 8 minutes

Both the American Academy of Sleep Medicine and the American College of Physicians note that there is not enough evidence to recommend the use of melatonin to address chronic insomnia and instead suggest cognitive behavioral therapy. However, hesitancy to recommend melatonin use appears to center less on concerns over efficacy and more on concerns over safety. 

Is melatonin safe?

Melatonin seems safe—our bodies make it naturally already! The pineal gland in our brains produces the hormone in response to the fall of darkness as a way of promoting and encouraging sleep. Artificial forms of light can block the production of melatonin. This is why sleep experts recommend turning off all screens at least two hours before you plan to go to sleep.

Since for many of us, winding down at night includes screen time—from watching television to gaming to working on the computer—taking a melatonin supplement to offset cases when our body isn't making enough seems like a straightforward solution.

Hesitancy to recommend melatonin use appears to center less on concerns over efficacy and more on concerns over safety.

But the synthetic melatonin that comes in a jar doesn’t work the same way as the melatonin produced by our brain. For starters, the melatonin supplement floods our body all at once rather than gradually building up with the setting of the sun. This rush might be one of the reasons for the extremely vivid dreams that many takers of melatonin report. And vivid dreams, of course, can affect our ability to sleep soundly.

And safe for some does not, of course, mean safe for all. The Mayo Clinic notes possible adverse interactions between melatonin and other medicines, including anticoagulants like blood thinners and drugs used to treat epilepsy and depression.

There are very few studies on the use of melatonin among children. In fact, melatonin is not registered for use in children anywhere in the world. Although limited, some of the existing studies suggest that melatonin shows promise for the safe and effective treatment of childhood sleep disorders. However, the NIH cautions that no long term studies have been done. 

The synthetic melatonin that comes in a jar doesn’t work the same way as the melatonin produced by our brain.

We know more about the effects of melatonin on other species. Studies have long shown that melatonin supplements affect the reproductive systems of rodents, sheep, and primates. Doses well below those that we give to our children show reduced fertility in rats and delayed onset of puberty in cats. Melatonin is, after all, a naturally produced hormone, and so to predict that it may have hormonal effects similar to those seen in other species would be a reasonable assumption.

Melatonin is poorly regulated in the United States

Adding to the uncertainties surrounding melatonin is that the supplement is only loosely regulated, at least in the United States. In many places, including Canada, the UK, the European Union, Japan, and Australia, melatonin is available only with a prescription from a doctor. But in the United States, you can buy it over-the-counter without a prescription. Melatonin is further considered a dietary supplement in the US, which means it is not as strictly regulated as other over-the-counter, nonprescription drugs. 

In the more extreme cases, the amount of melatonin found in the sample ranged from -83% to +478% from what was promised on the label!

In a 2017 study, scientists looked at 31 different melatonin supplements available for purchase in grocery stores and pharmacies. They found that the amount of melatonin found in more than 71% of the supplements they tested did not match the amount specified on the label within 10%. In the more extreme cases, the amount of melatonin found in the sample ranged from -83% to +478% from what was promised on the label! Even within the same jar/brand, dosages varied by as much as 465%. Although the authors declined to name the brands, the most variable was noted as a chewable tablet marketed for children.

Perhaps even more concerningly, the scientists found, using mass spectrometry, that 26% (or 8) of the supplements contained serotonin. Seratonin, a hormone with potentially harmful side effects if taken even in small doses, is considered a controlled substance and is used to treat neurological disorders.

Should you take melatonin?

A lack of long-term studies on the regular use of melatonin doesn't necessarily mean that if such studies were to be conducted the news would be bad. Instead, it means that we just don’t know.

If you're someone who takes melatonin regularly, you're taking on that risk to your long-term health. An investment in long term studies is clearly warranted, given the supplement’s popularity, and in the meantime, dosage regulation will be crucial for assuring its safety. 

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About the Author

Sabrina Stierwalt, PhD

Dr Sabrina Stierwalt earned a Ph.D. in Astronomy & Astrophysics from Cornell University and is now a Professor of Physics at Occidental College.