Many biological effects of melatonin are produced through activation of melatonin receptors,
while others are due to its role as a pervasive and powerful antioxidant, with a particular role in the
protection of nuclear and mitochondrial DNA.
In mammals, melatonin is secreted into the blood by the pineal gland in the brain. Known as the
"hormone of darkness" it is secreted in darkness in both day-active (diurnal) and night-active (nocturnal) animals.
It may also be produced by a variety of peripheral cells such as bone marrow cells,
lymphocytes and epithelial cells. Usually, the melatonin concentration in these cells is much higher than
that found in the blood but it does not seem to be regulated by the photoperiod.
In humans, melatonin is secreted by the pineal gland in the brain and is involved in the biochemical process
of sleep, as well as light-dark cycling.32 The pineal gland makes serotonin, which then turns it into melatonin
when light decreases. Strong light, such as sunlight, slows melatonin production, whereas a completely dark room
increases melatonin.
The hormone melatonin is used to treat circadian rhythm sleep disorders and some types of insomnia.
Taking melatonin as a supplement stimulates sleep and can have a direct sedative effect.
The body produces less melatonin as we get older, which may explain why elderly people often have difficulty sleeping
and why melatonin supplements improve sleep in the elderly. A study of middle-aged adults with insomnia compared
melatonin levels with that of people of the same age without insomnia. Those with insomnia had significantly lower
levels of melatonin.
Melatonin promotes sleep in children as well. In a study of children with sleep disturbances resulting from school
phobia, their sleep improved after taking melatonin nightly for three weeks. Other studies have shown melatonin
useful in treating insomnia in schizophrenics, people with jet-lag, and those working graveyard shifts.
Melatonin has been useful in helping people get off sleeping medication. A double-blind, placebo-controlled study of
34 individuals who regularly used benzodiazepines as a sleep aid, found that controlled-released melatonin taken
nightly enabled them to discontinue the use of the drugs.
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Attenburrow MEJ, Dowling BA, Sharpley AL, Cowen PJ. Case-control study of evening melatonin concentration in primary insomnia. BMJ 1996 May;312(7041): 1263-4.
Boutin, Jean A.; Audinot, Valérie; Ferry, Gilles; Delagrange, Philippe. Molecular tools to study melatonin pathways and actions. Trends in Pharmacological Sciences 2005, 26 (8): 412-9.
Caniato, R; Filippini, R; Piovan, A; Puricelli, L; Borsarini, A; Cappelletti, EM. Melatonin in plants. Advances in experimental medicine and biology 2003, 527: 593-7.
Cardinali DP. Melatonin. Physiology and clinical applications. Vertex 2007 Jul-Aug;18(74): 288-93.
Challet, E. Minireview: Entrainment of the Suprachiasmatic Clockwork in Diurnal and Nocturnal Mammals. Endocrinology 2007, 148 (12): 5648-55.
Conti, Ario; Conconi, Stefano; Hertens, Elisabeth; Skwarlo-Sonta, Krystyna; Markowska, Magda; Maestroni, Georges J.M. Evidence for melatonin synthesis in mouse and human bone marrow cells. Journal of Pineal Research 2000, 28 (4): 193-202.
Fredricks, R. (2008). Healing & wholeness: Complementary and alternative therapies for mental health. Bloomington,IN: Authorhouse.
Garfinkel D, Zisapel N, Wainstein J, Laudon M. Facilitation of benzodiazepine discontinuation by melatonin: a new clinical approach. Arch Intern Med 1999 Nov;159(20): 2456-60.
Haimov I, Laudon M, Zisapel N, Souroujon M, Nof D, Shlitner A, Herer P, Tzischinsky O, Lavie P. Sleep disorders and melatonin rhythms in elderly people. BMJ 1994 Jul 16;309(6948): 167.
Hardeland, RüDiger. Antioxidative Protection by Melatonin: Multiplicity of Mechanisms from Radical Detoxification to Radical Avoidance. Endocrine 2005, 27 (2): 119-30..
Ivanenko A, Crabtree VM, Tauman R, Gozal D. Melatonin in children and adolescents with insomnia: a retrospective study. Clin Pediatr (Phila) 2003 Jan-Feb;42(1): 51-8.
Maestroni, Georges JM. The immunotherapeutic potential of melatonin. Expert Opinion on Investigational Drugs 2001, 10 (3): 467-76.
Paredes, S. D.; Korkmaz, A.; Manchester, L. C.; Tan, D.-X.; Reiter, R. J. Phytomelatonin: a review. Journal of Experimental Botany 2008, 60 (1): 57-69.
Reiter, Russel J.; Acuña-Castroviejo, Dario; Tan, DUN-Xian; Burkhardt, Susanne. Free Radical-Mediated Molecular Damage. Annals of the New York Academy of Sciences 2006, 939: 200-15.
Singer C, McArthur A, Hughes R, et al. Melatonin and sleep in the elderly. J Am Geriatr Soc 1996; 44: 51.
Shamir E, Laudon M, Barak Y, Anis Y, Rotenberg V, Elizur A, Zisapel N. Melatonin improves sleep quality of patients with chronic schizophrenia. J Clin Psychiatry 2000 May;61(5): 373-7.
Tomoda A, Miike T, Iwatani N, Ninomiya T, Mabe H, Kageshita T, Ito S. Effect of long-term melatonin administration on school-phobic children and adolescents with sleep disturbances. Curr Ther Res 1999;60: 607-12.
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