Marilyn W. Edmunds, PhD, NP

Disclosures

February 05, 2003

Question

What are the data on safety and side effects of long-term administration of melatonin? Is there any information on use of melatonin with children?

Response from Laurie Scudder, MS, RN-C, PNP

 Response from Laurie Scudder, MS, RN-C, PNP Adjunct Assistant Professor, School of Health Sciences, George Washington University, Washington, DC, and Pediatric Nurse Practitioner in a primary care pediatric practice, Columbia, Md.

 

Melatonin is a naturally occurring hormone released by the pineal gland. Melatonin levels respond to an individual's natural circadian rhythms by increasing late in the afternoon/early evening and decreasing dramatically during the day. Light exposure, either natural or artificial, causes extremely rapid destruction of the hormone.[1] It has long been assumed that melatonin is responsible for sleep regulation, though the exact mechanism of action remains unknown.

Traditionally, it was believed that normal melatonin production decreased during adolescence, but a recent study that measured urinary metabolites of this hormone found that production remained virtually constant throughout childhood and adolescence; the perceived decrease was the result of stable levels in a larger body mass.[2] In fact, production remains constant throughout much of life.

Melatonin is 1 of only 2 hormones whose sale is not regulated by the US Food and Drug Administration. While not even available for purchase in some countries, such as Australia and the United Kingdom, it is sold over-the-counter in the United States.[3] While there is an enormous amount of anecdotal information available, there are few well-controlled studies that have examined safety, appropriate dosing including amounts and timing, use in special populations such as children or the elderly, side effects, or interactions with other products. However, the few published studies that have looked at use of melatonin in children have generally found the product to be safe, though most have focused on use in children with neurodevelopmental disabilities.

One study of 20 children with developmental disabilities found that children given melatonin fell asleep significantly more quickly, but did not experience overall longer sleep durations or wake less frequently.[4] A second slightly larger study of 46 children with neurodevelopmental disorders found that sleep improved in 34 of the children and none experienced side effects.[5] Only a very few studies have examined the use of this hormone in children without disability. For example, a study of 40 elementary school children without neurologic problems who were experiencing delayed sleep onset found that over the duration of the 4-week study, melatonin was relatively safe and significantly more effective than placebo in advancing sleep onset and increasing sleep. Of note, tests that examined attention span in these children found that, even in those whose sleep improved, measures of attention did not change.

The National Sleep Foundation[3] suggests that the product may be useful for teenagers who experience delayed-sleep-phase syndrome, an inability to fall asleep during the early nighttime hours that causes problems in awakening the next morning. However, appropriate dosing and duration of use in teenagers is not known.

Most studies have not reported significant side effects with use of the product. However, a newer study from the National Jewish Medical Center found that, in a small group of 23 adult asthma patients, melatonin could worsen asthma symptoms.[6] Anecdotally, melatonin has also been reported to worsen depression. Some patients report a "hangover" feeling after using this product.[7]

It should be noted that studies available have monitored use in children over a short period of time, as little as 1 month. In addition, the studies have focused on adolescents and older children, rather than infants and toddlers. While modest improvements in sleep have been found, those improvements are not due to fundamental changes in sleep hygiene. Without attention to critical lifelong good sleep habits, improvements are likely to be transient.

One area with substantial research is the use of melatonin for adults who experience jet lag. A recent Cochrane review[8] concluded that melatonin is effective in preventing or reducing jet lag, and occasional short-term use appears to be safe. The report recommended that its use be considered in adult travelers flying across 5 or more time zones, particularly in an easterly direction, and especially if they have experienced jet lag on previous journeys. Again, however, this recommendation is for adults and for short-term use.

The bottom line is that the "jury is still out" on long-term use of this product, particularly in younger children. For those nurse practitioners wishing to study the research, be cautioned that there are huge amounts of material available, ranging from scholarly works to some very questionable information. Claims have ranged from fantastic assertions that melatonin can increase longevity to modest claims that it is helpful for the prevention of jet lag.

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