Our planet has day and night and human beings are day living (diurnal) animals, that means we are awake in daylight and asleep in the dark (as opposed to nocturnal animals that hunt and are active during the night and sleep during the day). Our sleeping and waking cycles are set by daylight and dark.

We have two sleep hormones called melatonin and cortisol. Babies are born with a very free flowing sleep and wake rhythm as they have been living in relative darkness of the womb for nine months. However, their diurnal rhythm develops in the weeks after birth. There are vital things you can do to stimulate your baby’s melatonin production at night. This will help them be awake in the day and sleep at night.

Melatonin is known as the sleep hormone and it peaks in the bloodstream just before we go to sleep. It is known as the “sleep trigger”.

Cortisol is known as the stress hormone, but it is also the hormone that wakes us up. Cortisol levels are at their lowest level about 3-5 hours after we fall asleep. They then rise slowly through the night – to peak around 8am.

At bedtime, we want melatonin to be high and cortisol to be low. During the night, melatonin will decrease, and cortisol will rise. At a certain point, the hormone levels cross – and the cortisol level is higher. This is the point at which we wake up. This applies to adults as much as it does to babies and children.

The level of cortisol rises naturally throughout the night – its job is to wake us up.

However cortisol levels can also be increased by other things – such as stress. This is the reason that when you are stressed as an adult, you may find yourself waking up on the dot of 4 or 5am every morning.

The reason this is happening, is that your cortisol levels were too high (from stress) when you went to bed – so the melatonin/ cortisol cross over point was much earlier than it should have been in the morning.

For babies and children – one of the main reasons cortisol levels can be too high, is from sleep deprivation. Sleep deprivation leads to stress – which leads to increased cortisol.

This means they will be going to sleep at night with high cortisol – and therefore waking too early in the morning.

When adults are tired, they wind down. When babies and children are tired, they get “wired” and don’t sleep.

So a cycle of sleep deprivation can start very easily in babies and children.

Putting them to bed later, to try to get them to sleep longer, will make the problem worse.

Counterintuitively, they need to go to sleep earlier, and have the proper amount of naps through the day, in order to sleep longer at night.

In summary – if your baby or child is regularly waking up early, and not napping through the day – it does not mean they have had enough sleep. It means their cortisol levels are too high when they go to bed and you need to look at ways of reducing this.

Babies left to cry themselves to sleep have high levels of cortisol even when they were asleep and not crying.

Children left to cry uncomforted for prolonged periods during the day and night will produce elevated cortisol.

Think like a cave man!

When our cave dwelling ancestors approached night-time, it became dark and cool. These two factors triggered melatonin production which, in turn, triggered sleep.

Replicate this at home. Lower the temperature – around 18 degrees is right for the nursery or your room – and darken the lights.

TV and computer screens decrease melatonin and increase cortisol so turn them off at least an hour before bedtime.

A bedtime routine for babies will help them know what’s coming. They will relax more quickly and be ready for sleep.

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References are reviewed on a regular basis and are updated when applicable.