Does it work?
Some basics about melatonin, first.
- Natural (endogenous) melatonin is derived from the neurotransmitter, serotonin, in a chemical process which takes place only during the night. Endogenous melatonin is naturally low during the day and high during the evening as it is inhibited by exposure to light due to the ultrasensitivity of the pineal gland to circadian and seasonal rhythms and cues, the strongest of which is light.
- Melatonin is key to modulating the circadian clock in the brain because it signals day-night information to a specific pacemaker in the brain called the suprachiasmatic nucleus. However, secretion of endogenous melatonin is also easily altered by environmental factors like exposure to bright light during the evening or the introduction of a late meal or heavy exercise at bedtime. Other circadian rhythms in other parts of the body can be influenced by disruptions in endogenous melatonin secretion as well, including the digestive system, the systems which regulate core body temperature, even blood pressure and reproductive cycles.
- Endogenous melatonin also acts as a vasodilator in the skin, increasing blood flow which results in heat loss and lowered body temperature. These physiological processes, in turn, support the sleeping process.
- Interestingly, endogenous melatonin is not essential for circadian rhythms; the removal of the pineal gland shows very little impact on these rhythms in humans.
- Abnormalities in endogenous melatonin secretion are most commonly associated with the following three psychiatric disorders: Seasonal Affective Disorder (SAD) with winter depression, major depressive disorder, and premenstrual disorder (PMDD). These disorders, in turn, can have a major impact on sleep function, potentially leading to hypersomnia and overeating.
- While we secrete our own melatonin in the pineal gland, there is also a manmade form of melatonin (exogenous) which you can also take in pill form. It is rapidly absorbed (within 30 minutes) and has a 40-60 minute half life (meaning it is metabolized and eliminated within this amount of time).
- We can purchase exogenous melatonin as an over-the-counter drug because the FDA classifies it as a food supplement and does not require rigorous data supporting its safety, composition or effectiveness.
- The exogenous (manmade) form of melatonin is used in two ways: to potentially help shift circadian sleep phases into a more normal pattern, and to serve as a sleep inducer or maintenance drug. Its effect on the suprachriasmatic nucleus is directly related to the amount of endogenous melatonin already being supplied by the pineal gland: those with shortages in endogenous melatonin will feel stronger effects if they take exogenous melatonin.
- Studies show varying rates of therapeutic success in using exogenous melatonin. The risks of using exogenous melatonin are still unknown; no public health risks have emerged anecdotally. The most common potential side effect is headache. It is considered nonaddicting.
- Researchers still cannot agree on an optimal dosage of exogenous melatonin for most people as they have yet to discover a consistent dose-response relationship in studies (the lowest amount which can be shown to be effective).
- The effectiveness of exogenous melatonin depends upon the time of day it is administered, though researchers have yet to define an accurate window of time for taking it; the range is as broad as 30 minutes to 3 hours. It has been noted that if people take exogenous melatonin during the day, it may result in impaired function while driving a car, operating machinery or during job performance.
- The reason why research is so inconclusive about exogenous melatonin usage resides in the fact that while many studies have been conducted, the variables (dosage, type of subject tested, timing of dosage) vary wildly and cannot be cross compared.
Cleveland Clinic || Melatonin Supplement Review
Mayo Clinic/Dr. Brent Bauer || Is melatonin a helpful sleep aid — and what should I know about melatonin side effects?
Wise Geek || What Are the Pros and Cons of a Melatonin Sleep Aid?
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Resources consulted
"Biochemical Pharmacology of Sleep." Chokroverty, S. From Sleep Disorders Medicine; Butterworth Heinemann, 1999.
"Circadian Rhythm Sleep Disorders." Berry, RB. From Fundamentals of Sleep Medicine; Elsevier, 2012.
"Clinical Pharmacology of Other Drugs Used as Hypnotics." Buysse, DJ. From Principles and Practices of Sleep Medicine, eds. Kryger, Roth and Dement; Elsevier: 2011.
"Melatonin and the Regulation of Sleep and Circadian Rhythms." Guardiola-Lemaitre, B and Quera-Salva, MA. From Principles and Practices of Sleep Medicine, eds. Kryger, Roth and Dement; Elsevier: 2011.
"Pharmacologic Treatments: Other Medications." Krystal, AD. From Principles and Practices of Sleep Medicine, eds. Kryger, Roth and Dement; Elsevier: 2011.
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SleepyHeadCENTRAL strongly encourages people with ongoing sleep health problems to approach a medical professional to determine appropriate differential diagnoses and treatment. This post, like all other posts on SHC, is not intended to substitute for medical advice.
