What Is Melatonin And How Does It Affect Our Sleep?

Sleep contends in the same league as food, water and shelter when it comes to the very basic necessities to survive. A lack of sleep increases the risk of depression, heart disease, diminished cognition, memory impairments… the list goes on and on. The factors that influence sleep are numerous, such as mood, genetic dispositions, diseases etc. But, perhaps the most influential factor is exposure to light.

Sleep Inertia

A lack of sleep increases the risk of depression, heart disease, diminished cognition, memory impairments… the list never ends. Credits:PrinceOfLove/Shutterstock

The brain determines the degree of exposure by assessing the concentration of a particular hormone in our blood vessels. The concentration of this single hormone is known to have serious implications for sleep cycles, as well as reproduction. This hormone is known as melatonin.

Melatonin for Food

Melatonin is a small hormone whose secretion regulates sleep and other periodic activities in humans, as well as other animals. Spikes and slumps in its concentration allow an animal to discern vital information about the lighting conditions of its environment. The instructions to its organs are then given accordingly.

Melatonin structure

Melatonin structure. (Photo Credit : phenida@PHENTANYL / Wikimedia Commons)

For instance, a spike in melatonin implies that the lights have died; the Sun has set and it’s time to sleep. The brain then orders a decrease in motor activity, induces fatigue, and lowers the overall temperature of the body. On the other hand, a slump in melatonin communicates that the Sun is out and bright. This demands heightened attention, rapid response time and an energetic mood.

Melatonin is secreted by the pineal gland, which lies between the two hemispheres of the brain. This tiny gland is named so because its appearance is reminiscent of a pinecone. Animals with a pineal gland that malfunctions, whether due to natural circumstances or human interference, demonstrate a distorted pattern of sleep and reproduction.

Pineal gland brain

Pineal gland. (Photo Credit : Life Science Databases(LSDB) / Wikimedia Commons)

For instance, animals like hamsters breed in a particular season in which their gonads become activated. Other times, or in non-breeding seasons, their fecundity becomes impotent. Around the onset of the breeding season, the gonads must be rejuvenated. One major hint is the length of each day, or the photoperiod, which is determined by assessing the levels of melatonin in the body. Without a pineal gland, a hamster’s preparation for the breeding season would be incomplete, thereby leading to deleterious effects on the survival of the species.

Melatonin inhibits the function of gonads. With this knowledge, we can alter the procreation abilities of animals. For instance, sheep are known to breed only once in a given year; however, with careful melatonin treatment, they can be urged to breed twice!

Melatonin for sleep

The eyes are the windows through which light enters the body. A pattern of light and dark spots is etched on the retina, which is the projection screen of the eye. This information is relayed to the suprachiasmatic nucleus (SCN) in the hypothalamus, an area known to keep our biological clock ticking. The information then descends to the cervical ganglia through fibers extending from the hypothalamus. Finally, it is transmitted to the pineal gland via threads of neurons that climb upwards. There, melatonin attaches to two receptors, which we call Mel1A and Mel2B.

It is the dramatic dependence of melatonin’s synthesis on the operation of the eye that blind people find it notoriously difficult to fall asleep. On the contrary, sleep can be delayed by subjecting our eyes to a constant shower of bright light. While the Sun was the primary source of light for prehistoric man, the modern man discovered fire, invented lamps and now, phones. Yes, our smartphones have subtly distorted our biological clock.

Tired businessman sleeping on a laptop with clock in the background

The untimely rousing of our senses when they should be relaxing has adverse effects on our physical and mental health. (Photo Credit: Ollyy / Shutterstock)

However, it is only blue light that suppresses melatonin and replenishes cognition, blue light that so profusely emanates from our favorite devices. The untimely rousing of our senses when they should be relaxing can have adverse effects on our physical and mental health. This blue light is known to increase the risk of cancer, diabetes and obesity!

That being said, it is imperative to remember that these are merely correlations: blue light itself doesn’t cause cancer, or at least, we haven’t gathered substantial evidence confirming this. In fact, the true purpose of melatonin still eludes scientists. We only know that it is correlated to seasonal or Circadian rhythms and the onset of puberty.

Still, due to blue light’s disruptive effects on sleep, scientists recommend using goggles that are impervious to blue wavelengths, but welcome more red and green light. While red is the least harmful of all wavelengths, green light stretches the Circadian rhythm by half of what blue does (1.5 hours versus 3 hours).

internet addict man awake at night in bed with mobile phone

To avoid invigorating any of the melatonin hormones, avoid using your phone 2-3 hours before bed. (Photo credit: Focus Pocus LTD / fotolia)

If you can’t buy goggles, you can download display-altering applications like f.lux that suppresses the glut of blue emitted by your display. Or, to avoid invigorating any melatonin hormones at all, avoid using your phone 2-3 hours before bed.

Lastly, administrating melatonin has become a nifty solution to treat sleep disorders, but like any other drug, its dosage must be carefully formulated. Too low, and it is ineffectual, but too high and the slump in temperature can cause hypothermia! Supplements are known to neutralize jet lag and even deter insomnia. However, its safety is only guaranteed for temporary help; a lack of long-term studies prevents it from being sanctioned as a long-term remedy.


  1. Colorado State University
  2. Massachusetts Institute of Technology
  3. Harvard University
  4. National Institutes of Health (NIH)
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About the Author:

Akash Peshin is an Electronic Engineer from the University of Mumbai, India and a science writer at ScienceABC. Enamored with science ever since discovering a picture book about Saturn at the age of 7, he believes that what fundamentally fuels this passion is his curiosity and appetite for wonder.

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