Over-the-counter melatonin is fairly commonly being used by patients on their own as a treatment for insomnia, sometimes without the clinician even knowing about it. Patients often ask clinicians if it will be OK if they take melatonin. Also, some clinicians recommend melatonin to treat either insomnia, delayed sleep phase disorder, and several other conditions. For all these reasons, it is important that clinicians learn about melatonin.
What is melatonin?
It bugs me when patients (and even some scientific articles!) refer to melatonin as a “dietary supplement.” Melatonin is not something we require in our diet–it is a natural hormone that is produced (from the amino acid tryptophan) and secreted by the pineal gland. The secretion of melatonin is affected by the light-dark cycle and this hormone is very important in maintaining our circadian rhythm.
What does melatonin do?
It is important to realize that melatonin has two separate effects on sleep because these two effects are relevant to its use as a hypnotic and as a “chronobiotic” (medication that affects circadian rhythms).
1. Most importantly, melatonin alters the circadian rhythm, facilitating the onset of sleep indirectly. What effect it has on the circadian rhythm depends on what time it is given. Most frequently, it is given in the evening, in which case it tends to produce a phase advance, i.e., earlier onset of sleep. It is probably due to its chronobiotic effect that melatonin may help delayed sleep phase disorder and improv e circadian rhythm disturbances in persons who do shift work, have jet lag, or are blind (Zhdanova, 2005; Auld et al., 2017).
2. Melatonin also decreases alertness and the core body temperature, both of which make it more likely that the person will feel sleepy (Arendt and Skene, 2005).
Melatonin in older adults
Melatonin secretion is believed to decrease with age and, on an average, peak melatonin levels have been found to be lower in older adults (Zhdanova et al., 1998). But, this may not be true for all older adults (e.g., Zeitzer et al., 1999). The functional potency of melatonin receptors may also be lower in older adults (Zhdanova, 2005). These issues are important because it has been suggested that melatonin treatment for insomnia may be more helpful in older adults than in younger patients. Also, melatonin has been used in case reports and open-label studies to treat sundowning in patients with major neurocognitive disorder (dementia). Whether or not these uses are appropriate is discussed other pages on this website (see Related Pages below).
Does it work for the treatment of insomnia and/or of delayed sleep phase disorder? Is it safe to take–short term and long term? For answers to these questions, click on the links under Related Pages below.
Arendt J. Melatonin and human rhythms. Chronobiol Int. 2006;23(1-2):21-37. Review. PubMed PMID: 16687277.
Arendt J, Skene DJ. Melatonin as a chronobiotic. Sleep Med Rev. 2005 Feb;9(1):25-39. Review. PubMed PMID: 15649736.
Zawilska JB, Skene DJ, Arendt J. Physiology and pharmacology of melatonin in relation to biological rhythms. Pharmacol Rep. 2009 May-Jun;61(3):383-410. Review. PubMed PMID: 19605939.
Zeitzer JM, Daniels JE, Duffy JF, Klerman EB, Shanahan TL, Dijk DJ, Czeisler CA. Do plasma melatonin concentrations decline with age? Am J Med. 1999 Nov;107(5):432-6. PubMed PMID: 10569297.
Zhdanova IV. Melatonin as a hypnotic: pro. Sleep Med Rev. 2005 Feb;9(1):51-65. Review. PubMed PMID: 15649738.
Zhdanova IV, Wurtman RJ, Balcioglu A, Kartashov AI, Lynch HJ. Endogenous melatonin levels and the fate of exogenous melatonin: age effects. J Gerontol A Biol Sci Med Sci. 1998 Jul;53(4):B293-8. PubMed PMID: 18314560.
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