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Melatonin and Serotonin: How Hormones Help Us to Fall Asleep

Melatonin and Serotonin: How Hormones Help Us to Fall Asleep

There are many factors that can affect how well we sleep at night, but one which is often overlooked is our hormone levels. Besides helping us to reproduce, grow, and regulate our appetite, hormones also play an important role in regulating our sleep-wake cycle, or circadian rhythm. The three main hormones responsible for this are melatonin, serotonin, and cortisol. To give you a better insight into these three powerful hormones, we’ll take a look at their role within the sleep-wake cycle and discuss how each helps us to fall asleep.

What is a circadian rhythm?

Can you identify the points you feel more sluggish or energised during the day? This is down to your circadian rhythm or circadian cycle. Regulated by a collection of nerve cells in the brain called your hypothalamus, your circadian rhythm is the body’s 24-hour intrinsic clock that governs your sleep-wake cycle. Humans are diurnal, which means we’re programmed to rest at night and operate during the day. With good sleep hygiene, these highs and lows aren’t so obvious. But if you’re sleep-deprived, you may find yourself losing energy by lunchtime.

It’s also worth mentioning that your circadian rhythm functions best with order and routine. Practising good sleep hygiene and maintaining regular sleeping habits are essential to keeping your rhythms in order. Late-night parties, moonlight studying, and jet lag can run riot with your circadian rhythm and make you feel irritable. There are certain steps you can take to try and improve the quality of your sleep, so you can wake up feeling energised.

Which hormones are used to regulate sleep?



Production of melatonin is stimulated as darkness starts to fall, usually coinciding with sunset. Your brain starts releasing this chemical a few hours before you go to bed, signalling to your body that it’s time to wind down. Nowadays, staying awake with artificial lighting or looking at TV or phone screens can impact upon your natural melatonin production. Light stimulation can delay melatonin production to later on in the evening, depriving your body of enough time to relax before you go to bed. The blue light emanating from your electronic devices inhibits the production of melatonin, confusing your body as to when it should be asleep or awake.


Serotonin is often described as the body’s ‘happiness’ hormone. It’s a feel-good neurotransmitter that’s involved in countless bodily functions, including emotions, mood, appetite and memory, as well as sleep. While its exact function is still relatively unknown to scientists, high levels of serotonin are associated with wakefulness and lower levels with sleep. Serotonin is also unique in the fact that it makes us more energised as well as being an essential hormone in making us sleepy. Experts have found this hormone offers sleep-promoting brain factors and also promotes wakefulness.i It comes as no surprise, therefore, that serotonin deficiencies have been linked to sleep disturbances.


Often known as your ‘stress hormone’, cortisol levels peak just before you rouse in the morning. It plays the essential role of waking up the body, turning on your energy reserves and revving up your appetite. But since cortisol primes the body for action, it can make it much harder to sleep if secreted near bedtime, or frequently throughout the day during high-stress periods. That’s why prioritising relaxation techniques//B684REM sleep//B646sleep hub//H38.


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