Sleep is not just about routines, bedtime or sleep training methods. At the heart of your child’s sleep are two very powerful hormones working behind the scenes: melatonin and cortisol. When these two hormones are in balance, sleep comes more easily. When they are disrupted, sleep can become fragmented, unpredictable and down right, exhausting for both parents and children.
Understanding how melatonin and cortisol work, how they develop in babies and children, and how sleep training interacts with these hormones can completely change the way you approach sleep. Instead of guessing or feeling anxious about “doing the wrong things”, you can make informed, confident decisions that support your child’s biology.
This guide will walk you through everything you need to know, clearly, calmly and with no fear.
The Basics: Why Hormones Matter for Sleep
Sleep is regulated by the brain, not by willpower. Children do not “fight sleep” on purpose. When a child struggles with sleep, it is often their internal system is out of sync. Their are two hormones that play a central role in this:
- Melatonin: the hormone that signals sleep
- Cortisol: the hormone that signals alertness and stress
These hormones work hand-in-hand and follow a daily rhythm (circadian rhythm, AKA the body clock) and respond strongly to light, timing, routines, and stress. Sleep training, when done correctly works with these hormones, not against them.
Melatonin: The Sleep Hormone
What is melatonin?
Melatonin is often called the “sleepy hormone”, but it does not magically make you fall asleep. Rather, it signals to the brain that it is time to rest. Think of melatonin as the body’s night-time messenger.
Scientifically, melatonin is released by the pineal gland in the brain in response to darkness. When melatonin levels rise, the body begins to feel sleepy, calm and ready for sleep.
When do babies start producing melatonin?
What differs babies from adults is that babies do not yet have a mature melatonin rhythm. This develops as time goes by.
- 0 – 6 weeks: Melatonin production is minimal and irregular
- 6 – 8 weeks: Melatonin production begins
- 3 – 4 months: A more predictable circadian rhythm starts to form
- 6 months onward: Melatonin patterns become more established
Alongside the 4-month regression, this is one major reason why newborns have irregular sleep cycles.
Melatonin in Toddlers and Young Children
In toddlers and young children, melatonin is generally produced earlier in the evening (compared to adults). This means:
- It is best to put children to bed earlier
- Keeping children up too late can cause more problems
- Overtiredness can suppress melatonin release
When melatonin is released at the right time (every night), children fall asleep more easily and get longer stretches.
What Affects Melatonin Levels?
Several factors can have a direct impact with melatonin production.
- Light exposure: Bright lights (especially blue lights) can suppress melatonin. One of the biggest causes of this comes from our own devices – TVs, tablets and phones.
- Late bedtimes: Missing the ‘melatonin window’ can make children feel wired instead of sleepy. This is when you end up seeing a overhyped baby.
- Inconsistent schedules: When you do not have a consistent schedule, it does not give your child’s body the opportunity to learn what to expect next. It throws off the body clock.
- Overtiredness: Contrary to popular belief, being tired or overtired will not lead to more melatonin production. It will actually lead to less, making it harder to fall asleep and stay asleep throughout the night.
Sounds crazy, but sleep is indeed an art!
Cortisol: The Alertness and Stress Hormone
Cortisol is often misunderstood as the “bad” hormone and one that you do not want to increase. Cortisol is actually a very important hormone and one that has a direct association to survival. Cortisol plays a key role in:
- Helping us wake up in the morning
- Staying alert
- Responding to danger or stress
- Regulating blood sugar and energy
What we do not want is for cortisol to be released at the wrong times.
The Cortisol Flow
When thinking about healthy sleep-wake cycles, this is how cortisol plays out:
- Cortisol is highest in the morning, helping us wake up.
- Cortisol gradually decreases throughout the day
- Cortisol has the biggest dip at night, allowing melatonin to kick in.
Cortisol’s Link to Overtired Children
When children become overtired, cortisol levels rise to keep them going (yes, this also occurs in the evening as their body is now on overdrive). When a cortisol spike occurs, this can lead to:
- Bedtime resistance
- Hyperactive before bedtime
- Unable to fall asleep
- Multiple wake ups at night
- Early morning wake up
This is why, contrary to popular belief, the worst thing to do to your child is try to get them to feel overtired so they get a long stretch of night sleep.
Cortisol and Stress in Children
A major concern for parents when it comes to sleep training is the rise of cortisol and their children’s stress level. It is important to realise that short term cortisol strikes are in fact very normal and has no harm on your children. Of course cortisol spikes can come at various degrees, and therefore, it is recommended to choose the smoothest training methods.
It is also important to bear in mind that cortisol does not just spike when being trained. When your child is in fact overtired and over stretched, this also causes a cortisol spike. The main difference is cortisol spike with sleep training can be managed and is very short term, whereas an untrained baby will continue to have cortisol spikes on a daily occasion. This can come from:
- Inconsistent routines
- Missed naps
- Overstimulation / overtiredness
Melatonin and Cortisol: The Happy Marriage
Melatonin and cortisol work hand in hand and very much, in opposition. As melatonin rises at night, cortisol should fall and as cortisol rises in the morning, melatonin should fall.
This is why it is crucial to allow for this natural flow to happen. When overtired, when cortisol begins to be released and is too high at night, melatonin struggles to do its job. This imbalance is one of the most common reasons why children struggle to fall asleep and stay asleep.
Sleep Training
The goal of sleep training is to help your child fall asleep independently by linking sleep cycles. In order to this we need to help their body develop predictable sleep patters. It is by no means about forcing sleep or ignoring needs.
With sleep training, being consistent is the key to what allows hormones to regulate. When bedtime, routines and responses are all predictable, your child’s body will naturally know when to release melatonin and cortisol. The brain will simply learn what to expect.
Bedtime Routine
Bedtime routine is a perfect example, it is not just a habit it is a biological signal. Creating a calm, predictable and systematic routine can help lower cortisol, encourage melatonin release and prepare the nervous system to sleep.
Effective routines are always:
- Calm
- Screen-free
- Repetitive
- 30 minutes long
Night Wake-Ups
As highlighted in previous blogs, we all go through sleep cycles and have a brief awakening before drifting off to our next sleep cycle. When a child wakes between sleep cycles, their cortisol briefly rises. If your child is dependent on a sleep prop (external help – feeding to sleep, rocking, being held) to fall asleep, they will need help to go back to sleep as the cortisol would be high enough.
With sleep training, your coach will gentle teach the brain to
- Settle without cortisol spikes
- Transition between sleep cycles independently
- Maintain deeper, more restorative sleep
Therefore, sleep training is not about controlling children. It is more about supporting healthy brain development, protecting sleep quality, reducing chronic cortisol elevation, helping families function better.
When rested children are:
- More emotionally regulated
- Better able to learn
- More resilient
- Happier overall
Final Thoughts
Melatonin and cortisol and not bizarre scientific concepts, they are working with your child’s body clock day and night. When you understand them, sleep stops feeling like such a puzzle.
Sleep training, when done properly, supports your child’s hormonal balance and long-term wellbeing. It is not about perfection, ir is about consistency, predictability and trust in your child’s ability to learn new skills.
In the end, sleep is a skill. Hormones guide the process and with the right support, better sleep is absolutely possible for the whole family.