How Does Melatonin Affect Sleep?

12 min read

Last Modified 22 July 2022 First Added 21 July 2020

By Nat Took

Melatonin definition:

n. an amine hormone, produced mainly by the pineal gland as a metabolic product of the neurotransmitter serotonin, that helps to regulate seasonal changes in physiology and may also influence puberty. It is implicated in the initiation of sleep and in the regulation of the sleep–wake cycle. Melatonin has been investigated in clinical studies as a hypnotic and for the management of circadian rhythm sleep disorders. Although these studies are as yet inconclusive, melatonin is widely available as an over-the-counter medication.

Sleeping during the night and being awake during the day is a natural part of human life. This pattern is controlled by your circadian rhythm. You will probably notice that you are more alert or sleepy at different times of the day and the rhythm will rise and fall, again due to your circadian rhythm. This is all controlled by the Suprachiasmatic Nucleus (SCN) in the hypothalamus, which in turn controls body temperature and hormones that cause and stop sleep. One of these hormones is melatonin, which helps you to fall asleep.

What is melatonin?

Melatonin is a hormone that is naturally produced by the body. The hormone signals to the body that it is time to sleep. That’s why it’s often called the “sleep hormone”.

Discovered in 1958 by American physician Aaron B. Lerner and his colleagues at Yale University School of Medicine, melatonin was named for its ability to reverse the skin darkening effects of melanocyte-stimulating hormone. The chemical formula for melatonin is C13H16N2O2 meaning it contains thirteen atoms of carbon, sixteen of hydrogen, two of nitrogen and two of oxygen which are synthesised by the body through a variety of chemical processes from another hormone called L-tryptophan.

Released in humans by a small, pea-shaped endocrine gland in the brain called the pineal gland, melatonin is a hormone commonly associated with sleep. It’s primarily released at night, though is more accurately a regulating hormone that plays a part in many animal and botanical functions. This ranges from helping to synchronise circadian rhythms to triggering seasonal fattening, moulting and hibernation of animals. Melatonin is even responsible for defending against oxidative stress in plants.

Commonly used in the treatments of sleep disorders, though with mixed evidence of efficacy, it is a prescription-only medication in the UK. It is approved for medical use in the European Union, but has not received approval for medical use by the Food and Drug Administration (FDA) in the US.

Despite its uncertain effects as a medication, however, its role in the human body is not disputed – it plays an important part in the regulation of sleep cycles. The production of melatonin is directly influenced by the detection of light and dark by the retina. In short, our bodies find it more difficult to produce this sleep hormone when our environments are bright. On the flip side, dark bedrooms and a lack of light help our bodies increase our melatonin levels.

A second and interesting role of melatonin in the body is its connection to ageing. Melatonin is both an antioxidant and connected to the modulation of certain functions of the immune system. Its production declines with age, leading to scientific associations between melatonin and a number of age-related diseases.

So, what exactly are hormones?

Hormones are the body’s chemical messengers. They are released by endocrine glands and travel through your bloodstream to different parts of the body. They tell different tissues and muscles what to do.

There are three classes of hormones:

  • Eicosanoids;
  • Steroids;
  • Amino Acids.

Within these classes, hormones have a wide variety of chemical structures. The hormone binds to specific receptor proteins in cells which lead to the cell changing its function.

Hormones affect many processes in the body, such as mood, growth and metabolism. Generally, they regulate physiology and behaviour.

Where is melatonin produced?

In the body, melatonin is secreted by the pineal gland. The pineal gland is a small, pea-sized gland located just above the middle of your brain. In shape, the gland represents a pine cone, which its name is derived from. This gland is found in the brain of most vertebrates.

How melatonin works in the body

Once released into the blood, melatonin activates melatonin receptors, and it also has a role as an antioxidant. Sleep promoting effects have been linked to the activation of the MT1 (though there are other receptors that have different functions). When activated this receptor inhibits brain activity.

How melatonin regulates sleep

When you’re exposed to light, the light travels down the optic nerve of the eye until it reaches the SCN. The SCN then signals to produce hormones such as cortisol and to raise your body temperature, which causes you to start waking up. The SNC also inhibits the release of melatonin at this time. In the evening, when not as much light enters the optic nerve, the SCN stops inhibiting melatonin, which then starts the sleep process.

How can understanding melatonin help you sleep better?

If you’re having difficulty sleeping, it could be due to your exposure to light, which confuses your signalling system. Jason Piper, a certified sleep coach and founder of Build Better Sleep told us:

Melatonin is also known as the Dracula hormone because it only comes out at night. It is produced in the pineal gland and released when it is dark out. It helps us to feel sleepy, entrain our circadian rhythm, and is the body’s strongest antioxidant.

The body has natural rhythms that wake us up and put us to sleep. This is very useful. In the morning our cortisol levels naturally rise to wake us up and prime us for the day. Cortisol is useful in the morning as it makes us alert, clear thinking, and gives us energy. At night as the sun sets, our eyes register the changing light and melatonin is released so that we feel sleepy, so we can rest and repair the body overnight.

If you think back to a time before electricity, this worked perfectly. We were up at daylight to hunt,  farm, and gather. All of the days’ activities were done during daylight hours and then night time was dedicated to sleeping.

Fast forward to today, and most of us are living disconnected from our biological clocks and this is wreaking havoc on our bodies. We wake up and head off to spend most of the day inside a building under dim lighting, compared to the sun. We then come home and turn on bright lights, compared to what’s outside when it’s dark. This action tells the body it’s still daytime. This is why a number of people are having a hard time falling asleep. They are sending mixed signals to their brain.

In addition, Bart Wolbers, a researcher and science writer at Alex Fergus added:

Melatonin is often called the “hormone of darkness”. Levels of the hormone are increased after both blue and green light are absent from the environment. Blue and green light are part of the “visible light spectrum”, together with red, orange, yellow, and intermediary colours.

Traditionally, during millions of years of human evolution, sunlight was the main source of blue and green light exposure. Bright light that enters the eye suppresses melatonin levels and absence of that light, as you now know, increases them.

There are indications – although science is not 100% clear on this – that melatonin helps you sleep quicker, get into deep sleep, and aids in keeping you asleep.

The best way to boost melatonin levels, that doesn’t have any side-effects, is to wear red-tinted blue-blocking glasses before bedtime. The reason for wearing blue-blocking glasses at nighttime is because artificial light – coming from light bulbs, smartphones, television screens, billboards, and other tech – all put out unprecedented amounts of blue and green light.

Modern technology, since the invention of the Edison bulb in 1879, has thus altered the human relationship to dark and light rhythms. The campfires, oil lamps, and candles that were used before that time almost exclusively put out red and infrared light and don’t disrupt your melatonin levels.

As sleep is naturally regulated by day and night, it stands to reason that artificial light causes some of us to find it difficult to sleep. Blue light found in energy-efficient lighting and screens seems, in particular, to be disruptive. But it’s not all about light, there other areas that can also affect how well you sleep. If you want to sleep better naturally, try the following:

1. Reduce blue light exposure in the evening
2. Increase your exposure to bright light during the day
3. Reduce your caffeine intake later in the day
4. Have consistent bed and waking times
5. Minimise noise and light in the bedroom

Using melatonin supplements

If you find it hard to sleep naturally, you could try a melatonin supplement to help you to sleep. In the UK, melatonin is available as a prescription-only medicine and so needs to be prescribed by your GP. By taking melatonin you may help to induce your body’s sleep cycle.

Some people use melatonin for jet lag, to regulate sleep during shift work or for insomnia and other sleep problems.

Melatonin dosage

How much melatonin you should take varies between different people. Other factors, such as weight and overall health can affect how your body responds to the supplements. It’s advised by the National Sleep Foundation that 0.2 milligrams to 5 milligrams can be taken by adults. This should be taken one hour before bed.

When taking melatonin tablets it’s best to start with a low dose, so that you can check for side effects. If your sleep doesn’t improve, and there are no side effects, you can gradually increase the dose until you sleep better. However, you should not get over the 5mg dosage unless recommended by your doctor.

It’s possible to use melatonin for children, generally if they have a disorder that stops them from sleeping. Though children should take a much smaller dose than adults.

Do melatonin supplements work?

There’s not enough evidence to clearly say whether or not taking melatonin for sleep works. Some studies show that they do, whereas others prove the opposite. Every person also reacts differently to supplements.

There is evidence that melatonin can reset the body clock. Although it’s not clear if exposure to light is more effective. The research does suggest that if melatonin is taken at an appropriate time it can improve sleep when used for shift work and jet lag.

Dr Bay Kelly comments on melatonin:

Melatonin is a hormone that is produced by the pineal gland that assists in triggering sleep. Melatonin production is closely related to light exposure and is more effectively produced in the dark. Establishing a regular sleep and waking cycle with light cues, can significantly help encourage melatonin production. Melatonin is produced by transforming an amino acid called tryptophan, meaning that dietary factors can affect melatonin production. Tryptophan can be found in foods such as chicken, dairy products, eggs, spinach, nuts, seeds and salmon. It’s also important to know that in order for your body to produce sufficient amounts of melatonin from tryptophan, sufficient amounts of zinc, B6 and magnesium are needed. Melatonin supplementation in doses ranging from 1-5 mg have been shown to be effective in those with trouble sleeping due to jet lag or shift work.

However, on the question of whether melatonin supplements will help us sleep, there is some debate. Liz Brown, sleep science coach and founder of SleepingLucid, gave us her opinion on melatonin as a supplement:

Melatonin a hormone produced by the pineal gland and is most active at night. The unique thing about the melatonin hormone is that its production is heavily affected by light as it can only be produced when one is in a dim-lighted area. An increased production in melatonin makes sleep more inviting.

“Melatonin supplements are helpful for some people who experience sleep problems. These supplements can come in pills, chewables, and liquids. If melatonin supplements are helping you sleep, you can take one daily for the next two months and check if it does indeed improve your sleep. It’s also important to be relaxed and in a dimly-lit place after taking melatonin supplements.

Side effects:

Melatonin is generally considered safe, with fewer side effects than other sleeping medicines. However, side effects can include headaches, dizziness, depression and stomach upsets, among others.

It’s also important to note that melatonin can cause issues if you’re taking other medicines, such as birth control and diabetes drugs.

Caleb Backe, a Certified Personal Trainer and Health Expert for Maple Holistics says:

Your body naturally produces melatonin to help you sleep but sometimes it doesn’t produce enough. In such cases, a melatonin supplement can be used to aid sleep when taken in the correct dosage. If you’re sleeping at a time that is out of your natural sleep-wake cycle and your brain isn’t producing melatonin yet, then taking a supplement may be just what you need to fall asleep. Getting the right dosage of melatonin varies between individuals. Too much melatonin can disrupt your optimal sleep-wake cycle.

What effect does synthetic melatonin have on the body?

While we know the importance of biosynthesised melatonin to the body and various bodily functions, the impact of synthetic melatonin is less well understood. However, melatonin has shown greater than placebo effects for a variety of sleep related issues including the onset of sleep, total sleep duration and sleep efficiency.

Though these effects are relatively low, with onset between six to eight minutes, duration by around twelve minutes and efficiency at 2.2%, they have been confirmed by a number of studies, but also by meta-analyses (studies of studies) which, with a high degree of confidence confirmed the effects.

Evidence of efficacy has led to the use of melatonin for the following conditions:

  • Jet lag: – while evidence is more comprehensive for the efficacy of melatonin for eastward flights, reviews in 2010 and 2014 found better than placebo improvements in sleep for jet lag.
  • Delayed sleep-wake phase disorder: – melatonin was found in a randomised trial to improve the quality of sleep and sleep onset.
  • Some sleep disorders in children: – a literature review in 2019 found that melatonin showed better than placebo effects for children with a variety of autism spectrum conditions.
  • Anxiety prior to surgery: – a 2015 review found strong evidence that melatonin reduced anxiety prior to surgery.
Overall, it may be best to try and improve your sleep naturally before taking melatonin supplements. However, if you still can’t sleep, be sure to consult your doctor.

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