The Light and Dark Side of Melatonin

"Short-term melatonin use is generally safe in adults, but there is less known about long-term use," says Abigail Strang, MD, sleep medicine doctor, Wilmington, Delaware.

"Unfortunately, there has been insufficient research to confirm the long-term safety of melatonin," says David Neubauer, MD, Johns Hopkins University School of Medicine.

Melatonin supplementation has increased since the beginning of the pandemic when insomnia cases exploded.  "While there had been a steady rise in melatonin use from about 2010 to 2019, in 2020, there was a huge sales increase of 42% over the previous year," reports Neubauer.

Melatonin is a hormone produced in the brain's pineal gland in response to darkness. It assists with the timing of our circadian rhythm (our 24-hour internal clock) and with sleep. When daylight decreases, the pineal gland produces melatonin to prepare the body for sleep. 

More melatonin is released during darkness and less when exposed to light. Morning light causes the body to stop producing melatonin, but exposure to light during the night can block its production.

The melatonin sold in the U.S. is synthetic and is classified as a dietary supplement. It's sold OTC (over the counter) and not by prescription. Synthetic melatonin is unregulated since the FDA (Food and Drug Administration) doesn't regulate supplements. And because its production is not standardized, the quality of a given OTC melatonin product can be questionable because the amount of the hormone can vary.

In many other countries, melatonin is prescribed. Since there's so little regulation of dietary supplements, "One might consider purchasing melatonin with a USP Verified mark, meaning that the products follow some quality control measures," Strang says.

The AASM (American Academy of Sleep Medicine) states that a "USP Verified mark indicates that the product was produced in a facility following the Good Manufacturing Practices (GMP) Standards. These products meet some production quality control measures, including containing the amount of an ingredient on the label, without harmful levels of specific contaminants."

Be aware, though, that the USP Verified mark program is voluntary and that the AASM reports that "only four products, all with either 3 mg or 5 mg of melatonin, have received the USP Verified mark."

Neubauer reports that the FDA reviews neither the efficacy nor safety of dietary supplement products before selling them. "The FDA usually only gets involved if there are complaints of safety issues or when products make inaccurate health claims," he says.

Neubauer adds that unlike medications approved by the FDA for specific conditions, dietary supplements are not required to show they're effective.

The main reason people take melatonin seems to be to treat insomnia. Allison Freiman, 52, of Binghamton, New York, has been taking two 10 mg melatonin gummies every night for the past year. She says she doesn't feel tired at night when she doesn't take it.

"It helps me feel tired and relaxed," she explains. She did not discuss her melatonin use with her doctor or experience any side effects.

There's getting to sleep, and then there's staying asleep. "Research shows that melatonin may be beneficial in helping people fall asleep more quickly and that it might advance and stabilize the timing of the sleep-wake cycle," Neubauer says. However, he cautions melatonin is "less likely to help people remain asleep through the night."

Francisco Rodriguez, 52, of New York City, takes 10 mg of melatonin daily and has been using it for four years. "I decided to take it because I suffer from insomnia due to bipolar disorder," he explains. "It helps me get over the anxiety that develops with sleep deprivation." 

Rodriguez's nurse practitioner recommended melatonin. He reports no side effects and says he feels safe taking it.

According to Strang, "Melatonin can be effective in circadian rhythm disorders like jet lag and delayed sleep phase disorder, especially if used at certain times."

"In addition to using supplemental melatonin in these disorders, there are natural ways to increase your body's production of melatonin, such as adjusting exposure to bright light in the evening," she adds. "If insomnia is caused by other causes, such as anxiety before surgery, melatonin will be less likely to be effective."

Neubauer adds that melatonin "may be helpful in reducing jet lag symptoms and for certain other sleep disorders, such as REM sleep behavior disorder and circadian rhythm sleep-wake phase disorder, delayed type." 

He adds, "Since melatonin has antioxidant properties, it has been suggested as possibly helpful in a long list of other health conditions."

"Melatonin is available with a wide range of doses, some of which are surprisingly high," Neubauer says.  

"Typically, doses ranging from 0.5 mg to 3 mg are used for sleep onset difficulties. Unlike many medications where an exact dose is specified, there is less precision in melatonin dosing since it functions primarily as a signal to the circadian system."

Neubauer reports no "absolute contraindications to melatonin use," but cautions patients with autoimmune conditions and pregnant and lactating women to avoid taking melatonin.

Neubauer reports that while there is probably a slight risk of melatonin interacting negatively with other substances or medications, he advises caution in patients who take sedating medications, anticoagulants, antihypertensives, anticonvulsants and immunosuppressants. 

Of course, when taking any supplement, patients should let their PCP (Primary Care Physician) know if they plan to use or are taking melatonin.

Possible reported side effects include daytime drowsiness, headache, nausea, vivid dreams and nightmares. 

"Generally, melatonin is regarded as safe at recommended doses for at least short periods of time," Neubauer says.

As part of the aging process, melatonin production decreases. "Older individuals may have more medical conditions and may be on more medications," Strang advises, "so the use of melatonin supplements should be discussed with a health care provider to ensure safety and minimize drug interactions."

In general, if you're taking or plan to take melatonin (or any dietary supplement, for that matter), it's wise to discuss it with your doctor. 

Be sure to tell them all your medicines, including prescription, OTC medicines, supplements, vitamins, herbs and homeopathic remedies. This way, your PCP can "help with dosage, monitor for side effects, and ensure there are no drug-drug interactions," Strang says.

While melatonin can help treat children diagnosed with neurodevelopmental disorders, Neubauer recommends caution when using melatonin with children. 

"Keep it out of reach of small children, as there have been reports of overdoses," he says. "This is especially the case since gummy melatonin products can resemble candy."

For more information about children and melatonin, see the American Academy of Sleep Medicine's position here.