The short answer to your question is that for healthy kids, melatonin is probably safe and effective in small doses, under the direction of a physician, for two to four weeks. Outside of these conditions, things get more complicated.

Good quality sleep is essential for our health and well-being, so it is not a surprise that tired parents would like help in getting their kids to sleep better. Melatonin is a hormone produced by the brain following the patterns of darkness and light. Darkness stimulates its production, causing sleepiness, and light inhibits it, causing wakefulness. Melatonin has been used for decades in adults for sleep problems due to jet lag and insomnia.

Melatonin is the only hormone that is available in the US without a prescription. Curiously, the FDA has labeled melatonin as a "dietary supplement" even though it has nothing to do with nutrition. Because it is not categorized as a medication, melatonin manufacturers do not have to meet the standards of safety and efficacy as do other medications. Because there is no standardization of manufacturing, there can be variations in the absorption from brand to brand. Since melatonin is now being marketed for use in children, there is concern that parents may have the unfounded belief that this synthetically manufactured hormone is a "natural dietary supplement" which has been proven safe to use for kids as a long-term sleep aid — which of course, is not true.

There have been a handful of studies over the last twenty years on melatonin in children. Most of the studies were done in children with neurodevelopmental disorders like autism or ADHD, in whom disordered sleep is a serious problem. The studies show that melatonin does shorten the period of falling asleep by 15-25 minutes. The studies were less than four weeks in duration and there are not sufficient data to say whether using melatonin in children for periods longer than four weeks is safe or effective.

Minor side effects of melatonin can include headache, nightmares, decreased appetite, and drowsiness the next day. It may also interact with medications used to treat medical conditions, and with other hormones that affect fertility and sexual development. For these reasons, its long-term use in pre-pubertal children should only be on the advice of a physician.

Here are a few tips for establishing good sleep habits in kids:

Have a consistent bedtime routine with a stable bedtime and waking time, with age-appropriate expectations for number of hours of sleep

Look for cues of the natural evening melatonin surge in your child (yawning, and rubbing of eyes) and set her bedtime accordingly. Studies have shown that if a child's bedtime is set before the melatonin surge, then it will take longer for your child to fall asleep.

Don't inhibit the natural production of melatonin by too much light in the evening. Consider turning down the lights about an hour before bedtime

Avoid electronic use for at least an hour before bedtime. iPads and similar tablets emit blue light that inhibits melatonin production.

Morning sunlight is important for wakefulness in the morning, so pull back any light-blocking drapes in the morning before your child wakes up

Avoid the stimulation of exercise, big meals, and television for at least an hour before bedtime

If your child is still having problems falling asleep, then see your doctor.