Is melatonin safe for long-term use as a sleep aid?

Does melatonin actually help adults with chronic insomnia?

For most adults with chronic insomnia, melatonin does not meaningfully improve sleep. A 2022 meta-analysis of 24 randomized controlled trials found that melatonin was not significantly better than placebo at reducing the time it takes to fall asleep, increasing total sleep time, or improving sleep efficiency in adults without other health conditions [4]. This means that if you are an otherwise healthy adult struggling with insomnia, melatonin is unlikely to give you the extra sleep you might hope for.

Even in studies that did show a benefit, the effect was small. For example, in children and adolescents, melatonin increased total sleep by about 30 minutes and reduced sleep latency by about 18 minutes—modest gains that come with a threefold increase in non-serious side effects like headache and daytime drowsiness [1]. For adults, the evidence is even weaker: the same meta-analysis found no significant effect on these same outcomes [4]. So while melatonin is often marketed as a natural sleep aid, the data suggest its real-world impact is minimal for most adults.

Is melatonin safe for children and teenagers?

Melatonin should not be a first-choice treatment for children with chronic insomnia, and long-term use requires caution. A 2023 systematic review and meta-analysis of eight trials involving 419 children and adolescents found that while melatonin modestly improved sleep (30 minutes more sleep, 18 minutes faster falling asleep), it also increased the risk of non-serious side effects by more than three times (relative risk 3.44) [1]. The authors rated the evidence as 'very low certainty' and emphasized that melatonin should only be considered after sleep hygiene and non-drug approaches have failed, and only for short-term, carefully monitored use [1].

Long-term use is especially common in younger children, yet safety data are sparse. A Danish nationwide study of over 43,000 children and young adults found that 17% of 5- to 9-year-olds and 14% of 10- to 13-year-olds were still taking melatonin 12 months after their first prescription, often without breaks [2]. Many of these children had underlying psychiatric conditions, but the study noted that long-term safety data are lacking [2]. Another review of melatonin in children with autism spectrum disorder found that a prolonged-release formulation was safe for up to 3 months, with side effects like fatigue (6.3%) and mood swings (4.2%), but no effects on growth or puberty; however, data for immediate-release melatonin—the kind most commonly sold over the counter—are not available [5].

Worryingly, melatonin is being used in very young children without evidence. A 2024 survey of over 3,000 caregivers of infants and toddlers (0–36 months) found that 1.7% had given melatonin to their child, often without a healthcare professional's recommendation and for unsupported reasons like 'more restful sleep' [6]. The authors stressed that there are no safety or efficacy data for children under 2 years old [6]. Given the lack of regulatory oversight and the fact that melatonin supplements often contain different amounts than listed on the label, this is a significant concern [6][8].

Does the type of melatonin or dose affect safety?

Yes, the formulation and dose matter for both safety and effectiveness. Immediate-release melatonin is short-acting (3–4 hours), while prolonged-release formulations maintain therapeutic levels throughout the night [5]. The prolonged-release version approved for children with autism has the most long-term safety data, showing no evidence of tolerance, withdrawal, or effects on height, BMI, or pubertal development after extended use [5]. However, most over-the-counter melatonin is immediate-release, and its long-term safety has not been studied [5].

Dose also plays a role. A 2023 randomized trial of 1,793 adults found that 5 mg of melatonin was safe (12% reported mild side effects, none severe) and improved sleep quality, but it was no more effective than 15 mg of CBD alone [3]. Higher doses are not necessarily better, and they may increase side effects like headache and drowsiness [7]. The most common side effects across studies are mild—headache, daytime sleepiness, and gastrointestinal issues—but serious adverse events have not been systematically tracked in long-term use [1][7].

Drug interactions are another consideration. Melatonin is metabolized by the liver enzyme CYP1A2, so medications that affect this enzyme (like some antidepressants, caffeine, and the blood thinner warfarin) can alter melatonin levels [5]. This means that if you take other medications, the safety profile of melatonin may change, and dose adjustments might be needed.

About These Sources

This answer is built on 8 peer-reviewed studies — published from 2022 to 2024, 2 from 2024 or later, 5 in Q1 journals, collectively cited 265 times — selected as the most relevant from 12 studies that passed quality screening, drawn from 65 papers retrieved from a database of over 500 million.

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