Melatonin, a hormone naturally produced in the body, is sold over the counter (OTC) in the United States as a dietary supplement that induces sleep. The body produces melatonin at sunset every evening to prepare the body for sleep while it’s dark outside. Because it’s a naturally occurring hormone and because it’s readily sold OTC, many consumers consider the drug to be quite harmless. An Australian physiologist who’s studied the drug for 40 years, however, has recently issued a call for caution, especially when it’s given for children’s sleep problems.

Professor David Kennaway, Head of the Robinson Research Institute’s Circadian Physiology Laboratory at the University of Adelaide, South Australia, says the drug is not as harmless as many people think. His studies indicate serious side effects could occur in older children who were given melatonin for early childhood insomnia.

Melatonin is widely used in the livestock industry due to the physiological changes it causes to many body systems. It’s fed to goats and sheep to alter their seasonal sleep patterns so they produce more milk. Egg-laying poultry get melatonin so they will lay more eggs. Cattle earmarked for livestock shows, the beauty contests of the ranching industry, get melatonin supplements to stimulate lush hair growth during the summer.

“If doctors told parents that information (melatonin’s veterinary uses) before prescribing the drug to their children, I’m sure most would think twice about giving it to their child,” says Kennaway. In Australia, melatonin is a prescription drug approved to treat insomnia in patients 55 and older but it is frequently prescribed off-label (outside the limits for which it is approved).

The drug is sold as an OTC dietary supplement in the USA. As such, it has never been approved for use by the US Food and Drug Administration (FDA) and has never been systematically tested for safety and efficacy. Melatonin can be freely marketed in the US as long as labels and packaging literature do not claim the product will prevent, treat, or cure any specific ailments.

There is extensive scientific evidence that melatonin causes physiological changes in animal body systems that regulate reproduction, immunity, metabolism, and the cardiovascular system. There is little systematic study of the drug’s effectiveness and safety on humans of any age.

“Considering the small advances melatonin provides to the timing of sleep, and considering what we know about how melatonin works in the body, it is not worth the risk to child and adolescent safety," Kenneway says. Another concern is the potential for adverse drug interactions when it’s given to children who are also taking other medications, be they prescribed or OTC; without systematic testing in humans, the risk of adverse drug interactions is unknown at this time.


  1. "Warning On Use of Drug for Children's Sleep." The University of Adelaide News & Events. The University of Adelaide, 25 Feb. 2015. Web. 2 Apr. 2015.
  2. "Melatonin." American Cancer Society. American Cancer Society, 1 Nov. 2008. Web. 2 Apr. 2015.
  3. "Insomnia in Children." Cleveland Clinic Children's. Cleveland Clinic, 30 May 2013. Web. 2 Apr. 2015.
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