Baby sleep is complicated.
Once you have a baby you quickly learn that "sleeping like a baby" is a myth. A baby fighting sleep is one of the most common problems across families.
Even when all conditions are optimal for sleep, most babies cannot roll away and fall asleep like adults. Neither can they stay asleep for long stretches.
But why do babies fight sleep? How are their systems different than us that makes it hard to put themselves to sleep and stay asleep?
I got curious from a nervous system perspective and researched the topic.
In this article I explain why babies fight sleep using what science has discovered about sleep mechanisms of adults and babies, as well as how baby brain is different than adults.
How do we sleep?
Humans are wired for sleep at birth
Contrary to popular belief, babies know how to fall asleep by nature. Imagine your baby's life in the womb. Unborn babies are capable of falling asleep and waking up.
To understand how, let's have a look at how human body goes from wakefulness to sleep.
Our sleep is regulated by two mechanisms: circadian rhythm and sleep hemeostat.
Circadian rhythm follows Earth's rotation
Circadian clock is our natural, internal clock that is synchronized to the 24-hour rotation of the Earth. Circadian clock lets our body adjust to day and night cycles.
The word circadian comes from Latin. Circa means "around" and diēm means "day".
Circadian clocks are observed not only in animals, but also in plants, fungi and cynobacteria. In 2017, scientists who discovered how the circadian clock works won The Nobel Prize in Physiology or Medicine 2017. Their research revealed that the clock is controlled by certain genes and the proteins those genes encode.
In short, our genes are responsible for our circadian clock.
Although not clear when our circadian rhythm develops in the womb, we know that it is certainly formed by the third trimester. This is one of the explanations of how unborn babies fall asleep and wake up.
Sleep homeostat measures "sleep pressure"
Sleep homeostat is a biological sensor measuring our need for sleep at any given time. This need is also known as "sleep pressure." Sleep hemeostat is controlled by our hypothalamus.
Our body constantly measures sleep pressure. Sleep pressure is highest at night. This coincides with our circadian rhythm.
Babies and adults alike, we have a total daily sleep need that needs to be met. If our circadian timing and sleep pressure coincide, we can fall asleep easily. We can achieve this by going to bed when we are tired and sleeping for the right amount of hours. This amount should be long enough to give us rest and short enough to become tired again for next night's sleep.
Light resets our clock
Circadian rhythm is controlled by a small region in the hypothalamus called suprachiasmatic nucleus (SCN). SCN is the master clock in our body. The firing of the SCN neurons instructs our brain and other organs about what time of the day it is.
When we wake up in the morning, some specialized cells in the back of our eyes called the intrinsically photosensitive retinal ganglion cells (ipRGCs) get activated and pass the message "there's light" to the SCN.
Light is the main synchronizer of our clock. (Temperature and food are others.)
Biological rhythm settles gradually
Although it is known that newborns quickly adjust to light and dark exposure, other aspects of their biological clock is not matured.
For example, their cortisol rhythm is the opposite of an adult's. Adults have higher levels of cortisol in the morning. Cortisol levels of fetuses and newborns, on the other hand, are higher in the evening, when they are supposed to be winding down.
Melatonin rhythm is also not present until babies are 2 months old.
In short, newborn babies don’t know what time of day it is. They establish a rhythm by approximately 4 months of age.
Babies sleep differently than adults
Although the main 2 mechanisms (circadian rhythm and sleep hemeostat) are present in both adults and babies, baby sleep is a little different than adult sleep.
Adults spend 20-25% of the night in REM (rapid eye movement, in other words, active) sleep. Our sleep cycles take 90-120 minutes.
In babies, REM and non-REM (deep) sleep share equal percentages. Also, a baby's sleep cycles are shorter. They last only about 50 minutes for the first nine months.
Why do babies spend more time in active sleep?
Babies benefit from shallow sleep because their needs are frequent. By staying in REM sleep for longer, they make sure to wake up to express their needs. The frequent need to be fed is a good example.
Adults wake up in between sleep cycles, but we don't put much thought into it. We might turn our pillow, change position, even visit the bathroom, and effortlesly, get back to sleep.
Babies wake up in between their sleep cycles too. But unlike adults, they might need help putting themselves back to sleep. You might be curious why. I will explain this in a minute.
Sleep cannot be taught but self-regulation can (over a very long time)
Most people think that sleep can be taught. But children's bodies know how to sleep.
The problem with baby sleep is that babies cannot take the necessary steps to bring themselves to the edge of sleep. In other words, a baby's self-regulation skills take time to mature.
Imagine how you prepare yourself for sleep. You plan to stop eating after a certain hour before bedtime. Maybe you take a bath. You may also be putting on your favorite pjs to get in the mood. Watching or reading something are also good ways to wind down.
In bed, you might place your pillow in a particular way. You might pull your leg towards your stomach, or lay on your belly in order to fall asleep.
All of these are the things you do (maybe even without realizing) to bring your nervous system to a state that's suitable for sleep.
A baby has similar needs to wind down. But they cannot anticipate sleep from hours in advance, like adults do. Because they cannot prepare themselves for sleep, their nervous system needs help to transition into an unconscious state.
Now let's have a look at why self-regulation is crucial for unassisted sleep.
Self-regulation is our ability to redirect our emotions, thoughts and behaviors. Some self-regulation examples are calming down after feeling frustration, focusing on a task, or changing our behavior according to expected outcomes.
Self-regulation is an imaginary brain muscle. We use it intentionally. Getting ourselves to a sleepy state is a self-regulation outcome. Same applies to going back to sleep after an interruption.
In sleep training contexts, self-regulation is referred to as self-soothing.
Sleep experts and some of the very tired parents rush to teach babies self-soothing. Several training methods are common. Most of these methods involve letting babies "cry-it-out" for varying amounts of times with varied amount of parental support. Behaviorist perspective says that these methods teach babies to be independent.
To understand why this is misleading, let's see what baby brain looks like.
Developed hippocampus and amygdala, undeveloped prefrontal cortex
Babies are born with a developed hippocampus and amygdala. Hippocampus is responsible for learning and long-term memory, and amygdala is responsible for memory processing, decision-making and emotional responses. These responses include our fight-flight-freeze reactions to stressful situations.
Baby brain does what it has to do. It learns and it reacts to danger.
This means that babies are wired to feel fear and other strong emotions when they are in stress.
Sleep is unknown territory for babies. It is a state of total vulnerability. If we were living in the wild, sleeping in unsafe settings would cost us our lives. Babies are coded to survive. For the same reason, they want to be safe in their sleep.
When babies get stressed in bed, their amygdala makes sure to trigger fight-flight-freeze response. For us adults, there is only one way to get out of that response and that is to engage our sense-making brain parts.
The part of our brain that is responsible for logical reasoning is the prefrontal cortex. Prefrontal cortex is important for decision making and moderating social behavior.
Prefrontal cortex has a big part in self-regulation. The important thing is, when babies are born, their prefrontal cortex is not matured. In fact, it keeps developing and maturing until our mid-twenties!
Human brain takes time to mature. Expecting a baby to self-soothe ignores human brain's developmental steps.
3 ideas to help baby brain sleep better
When it comes to baby sleep, behaviorist models seem to dominate the space. While it is true that sleep is a behavior, we must consider all the unknowns behind this behavior before we take actions to alter it.
Just like other human behaviors, behaviors of babies and children should be looked into with curiosity.
What causes "bad" sleep behavior?
There are so many unknowns to this question. Science has still a lot to discover on sleep and baby brain.
However, we can use our knowledge on brain to help our babies sleep better. Of course, love, tolerance, compassion and empathy should always lead the way when in doubt.
Here are 3 ideas to help you investigate your baby's sleep:
1) Watch for circadian rhythm and sleep pressure
"Put your baby on a routine" is a common advice that circles around. This advice makes sense if we use it mindfully. A good start is arranging our baby's day according to their body's needs, rather than strict schedules posted online.
Babies and adults go to sleep more easily when the circadian rhythm and sleep pressure overlap. This means, we can drift off more easily when we are "tired enough" in the "right time of the day".
Finding the overlap might be tricky for parents. That's why observing awake windows and adjusting sleep times according to the baby's cues is a good idea.
Most parents notice sleep signals a lot later than children start giving them away. Some observation will do the trick.
For example, a first sleep cue can be the baby's blank stare or lack of enthusiasm towards activities they normally care about. Scratching ears, rubbing eyes and yawning follow. When the baby has gotten to the stage of crying for sleep, they have already become overtired and you might have missed the sweet spot for sleep.
Watching the sleep cues give you the opportunity to move the baby to a calm space where there is little stimulation. A calm environment is the first step of putting our body to sleep.
2) Expose the baby to natural sunlight during the day, go for red light during the night
Light resets our circadian clock. But not all light is the same.
Sunlight is white, but it consists of different wavelengths, thus different colors of light. (Imagine a rainbow.)
Morning sunlight has a higher proportion of blue, while evening light is higher in red.
Blue-rich daylight signals daytime to our circadian clock. It increases alertness by elevating the hormones cortisol and serotonin and by suppressing the sleep hormone melatonin.
Our living room, although a well lit one, has five times less light than a gloomy day outside and 30 times less light than a sunny day. That's why it's important to expose our children to natural daylight every day.
When the evening settles, we can try to diminish artificial lights. We will still need light during bedtime and night wakings though. To get around this, we can use red lightbulbs. Red light does not disturb sleep because its long wavelength does not intervene with our melatonin rhythm.
3) Help baby's self-regulation through co-regulation
Babies might get stressed out during the day because of multiple reasons we might not be aware of.
They might be scared of a facial expression and bottle up the feeling. They might be having a hard time adjusting to their new skills. Whatever the reason might be, babies can go to bed with lots of feelings.
Adults are not much different. We too run a checklist of our day right before we go to sleep. We want to settle conflicts with our loved ones. We turn to our partner for extra comfort. All of these are the things we do to settle our nervous system to transition to a sleepy state.
Similarly, a baby needs help with self-regulation before and during sleep. This is no different than a baby's need for support when they encounter a stressful situation during the day. After all, parenting and nighttime parenting are not two separate things.
For example, imagine a leashed dog barking at your kid from a distance. Your kid is not in physical danger but still, she is under stress. Her body reacts to stress with fight-flight-freeze response. Her reasoning is not matured yet and it's clear that she cannot calm herself down using logical arguments ("a leashed dog cannot harm me"). What would you do other than holding her close and telling that it is going to be all right?
Pre-sleep stress is no different. It takes tolerance and time to teach your baby to self-regulate. The most straightforward way is to "lend" your regulation skills to her. This is called co-regulation.
One way to co-regulate is to respond to our child's needs with sensitivity. According to research, a parent's emotional availability in sleep settings promotes feelings of safety and security, resulting in better-regulated child sleep.
In another research, mother's support in early childhood had a relationship with healthy development of hippocampus, a brain region key to memory and stress modulation.
But we cannot rush self-regulation. It's a long process mirroring our parent-child relationship. That's why, letting babies cry on their own is far from teaching them how to calm their difficult emotions.
In fact, research showed that babies left to cry-it-out did learn to cry less and go to sleep faster. The interesting part is, their cortisol levels sky-rocketed even though their behavior did not show stress. What's more, because these babies did not transmit any stress signs, their mothers' cortisol levels dropped, causing an asynchronization in mother-baby physiology.
Brain and sleep knowledge can enlighten our very unique journey of parenting. If we have a baby fighting sleep, we can start observing our baby for her developmental and emotional cues. This way we can lean on our parenting instincts with greater confidence, finding courage in what our heart tells us to do.
Key take aways
😴 Sleep is complicated and baby sleep is even more complicated. Science has still a lot to discover in both domains.
🛌 Body systems and daylight has a strong relationship. The time we go to sleep and how tired we are influences our sleep.
💤 Baby brain already knows how to sleep. But they need help to bring themselves to a sleepy state.
😌 Self-soothing should not be rushed. Human brain matures over a long period of time.
❤️ Knowing about developmental stages of the brain can free us of complicated parenting advice.