Is Child Sleep Developmental?

“Don’t worry about it, it’s developmental. She’ll sleep when she’s ready.”

I’ve seen and heard this advice given to tired moms by many well-meaning women across social media platforms, at play dates and in online moms’ groups. While many things regarding children, their habits and behavior have developmental aspects, and have to do with their development, I think “developmental” has become a bit of a trendy word. When put on the spot I doubt a whole lot of people could give an answer about exactly what this means. In this post, I’d love to dig into this a bit and answer the question- is child sleep developmental?

What does “developmental” mean?

Regarding children, developmental is a word that simply means anything concerning their natural development. I suspect that when people make claims that something is “developmental,” they actually mean that it is a developmental milestone, which is a behavior that cannot be achieved before a child is physically, cognitively, or emotionally ready.

Is sleep a developmental milestone?

No. Developmental milestones, by their very definition, happen during predictable ages for all children, with the exception of children who have delays and/or need interventions. Children develop in five main categories- cognitive, social/emotional, speech and language, fine motor skills and gross motor skills. Some examples of developmental milestones are learning to smile, crawl, walk, imitate sounds, wave, or tie your shoes. Most typically abled children hit these milestones within a few weeks or months of each other depending on the milestone, and once they achieve a milestone, they can’t “lose” it without some kind of significant event, illness, or trauma.

For clarity’s sake, let’s say we are talking about “sleeping through the night without intervention” or “sleeping at night without a significant amount of wakings.” Some newborns will surprise their parents and sleep through the night at a very young age. After working with hundreds of families, I know some families with 3, 4, and 5 year olds who have never gotten through a night without significant wakings and disruptions, even once. These same families are sleeping through the night within two weeks of responsive but consistent behavioral interventions.
With developmental milestones, it’s impossible to make the milestone happen before it is supposed to happen with behavioral interventions. Let’s talk for a moment about something us child development nerds know as the zone of proximal development. This term was coined by the psychologist Lev Vygotsky, and refers to the range of things that children can learn to do independently, with temporary assistance from a caregiver. Look at the image below- the zone of proximal development is between what a child is capable of doing independently and what they can’t do at all. Adults provide something called scaffolding, essentially bridging the gap and facilitating learning of a skill to move that skill from the zone of proximal development to something the child can do independently.

Imagine a child learning to read, with an adult sitting nearby. As a child gets stuck on a sound, the adult might help them sound it out to assist, teach them any sounds they may not know, and prevent frustration. As time goes on, the adult might wait longer and longer to jump in to help, as the child becomes more proficient in reading. Eventually, the child can sound out the words themselves! Now we can apply this to sleep. A baby may be struggling to connect sleep cycles and form the habit of falling asleep without intervention. An adult can scaffold this skill by providing an appropriate schedule, a good sleep environment, an opportunity to practice the skill as well as comforting if or when the baby gets frustrated. Eventually, they pull back that help little by little until the baby is falling asleep independently with no trouble. If the baby wasn’t developmentally able to progress in this skill, it would simply be impossible, with or without scaffolding, to develop.

A simpler way of explaining the zone of proximal development is an amazing phrase coined by Maria Montessori, “Help me to do it myself.” Children want (and need!) to be independent, but also need help and encouragement to get there. We should encourage and allow children to conquer skills that they can conquer!

For example, if you held your three month old by the hands and tried to make them practice walking for hours each day, you still couldn’t make them walk at 3 months old. If you showed your 12 month old over and over how to hold scissors and cut paper, they still wouldn’t have the fine motor skills to hold scissors and cut paper. They are physically, cognitively and developmentally incapable of doing so. Contrast that with behavioral sleep interventions, and almost all childrens’ sleep will improve greatly with behavioral interventions within days, from the very first day you bring them home from the hospital. No, I’m not even talking about full blown sleep training, but using flexible schedules, habits and routines from day one can help immensely in shaping the quantity and quality of sleep for your child and family. Clearly, sleep is something that is greatly affected by habits, and children are capable of independent sleep from an early age.

Good sleep quality and quantity, because it is so based in habits, is also something we can lose! Every parent knows that after a week on vacation and off schedule, sleep becomes a challenge when you get back home. Even us adults can get in the habit of a little too much Netflix before bed, staying up too late, or increasing our caffeine intake, and before we know it, we’ve gotten into a cycle of poor quality sleep. It is so clear how habits affect our sleep, whether we are discussing baby sleep or adult sleep!

So, even if it’s not a milestone, is sleep developmental?

There are certainly developmental considerations when it comes to sleep! Regarding child sleep, there are factors to be respected that have to do with a child’s development that make expectations surrounding sleep either “developmentally appropriate” or “developmentally inappropriate.” Let’s talk about some of these.

Developmental factors that affect sleep:

Newborn: When babies are first born, it would be developmentally inappropriate to expect certain things regarding their sleep. For example, because their little tummy is the size of a cherry when they’re born, we can’t expect them to sleep longer than around 3 hours without needing a feeding. And while some babies can fall asleep without intervention, we can’t expect that of all babies. Sleep happens when needs are met and babies are comfortable enough to sleep. Think about this- just a few short days or weeks ago, your baby was inside of you, having every need met. It was the perfect temperature, the perfect snugness, they were never hungry, and they didn’t know what a cold wet diaper felt like! Now, they’re learning to live in a world where they are separated from your body and they do get hungry, too cold, too warm, startled, tired and overstimulated. Any number of these things could make it difficult for them to fall asleep without extra soothing measures like sucking to sleep or rocking to sleep. So while you can start to practice putting them down awake (and if the thought of practicing without concrete “results” doesn’t stress you out in this postpartum period, then you absolutely should practice!), you can’t expect every baby to be able to obtain this skill before around 3 months of age. For reference, I practiced with my second son every single day, and the first time he ever fell asleep independently without nursing, rocking or being held was 7 weeks old.

Around 4 months of age, sleep cycles become more like adult sleep cycles. Though sleep cycles continue to be about half the length of adult sleep cycles (therefore providing twice the opportunity as adults have for night wakings!) there is nothing more to “wait for” in terms of sleep cycle maturity. They go through the same phases as adult sleep in the same order. However, at this age, the majority of babies still need a night feeding, and therefore you can’t necessarily expect consistency in “sleeping through the night.”

Around 6 months of age, give or take a little bit, infants experience a cognitive change called object permanence. This can cause separation anxiety. The best way to help a child learn to be comfortable again during a period of separation anxiety is to play peekaboo, walk around the corner and pop back out, or leave the room for a moment and come back. Just like when you leave a child at daycare or with a babysitter (even if the babysitter is a beloved grandparent OR EVEN THEIR OTHER PARENT!) and they cry because of the separation, sometimes a baby will cry at bedtime because they anticipate the separation. However, the way to help them through this and become comfortable again is not to never leave their sight. The way to help them through this is to show them that, over and over, when you leave, you always come back. 

Around 2-3 years old, when imagination develops, children become capable of having nightmares, as well as being “afraid of the dark.” These are real fears and should be considered and addressed. However, think about how we address other fears our children have about necessary things- for instance, going to the doctor for a shot. We may give extra comfort, help them play doctor, let them watch videos, talk them through things, but ultimately, we help guide them through the fear and still take them to the doctor for their shots. You should give extra reassurance, but should not create a long-term dependence on you for your child to be able to sleep.

During other developmental milestones being hit from infancy through toddlerhood, sleep can be disrupted. Have you ever noticed that when a baby learns to pull up to standing, or learns to crawl, that sleep gets a little messy? It’s because they are being biologically driven to practice this skill until they perfect it, even between sleep cycles and while asleep! Anticipate these changes and developmental considerations, and just try not to fall back into too many dependent habits during these times.

Note: This is not an exhaustive list of developmental factors that can affect sleep, but I hope it gives you an idea of what you can expect, how child development can impact sleep and other behavior, and thoughts on how to get through it!

If sleeping through the night isn’t developmental, what is it?

Sleep, and how well we sleep, is mainly a combination of personality and behavior, or the age old duo of nature and nurture. Essentially, how well we naturally sleep from the getgo often comes down to temperament, and how well we sleep overall comes down to environment and habits, which you as the parent provide for the child! Some habits are correlated with reduced sleep quality, and some habits are correlated with better sleep quality. Habits like keeping a consistent bedtime routine, an age appropriate schedule, and teaching your child to fall asleep and back to sleep without needing intervention are proven through research to improve sleep quality. This means that how well your baby sleeps can absolutely be molded through behavioral strategies such as sleep training.

If sleeping is essential, shouldn’t it just come naturally?

Truly one of life’s great questions, ha! But in all honesty, you could say that about many things. Plenty of us need the help of skilled lactation consultants to successfully breastfeed. Some children even need frenectomies to release tongue ties in order to transfer milk successfully. Many children benefit from physical and occupational therapy in order to achieve things that come more easily to others. Sleep does come easily to some people, but for others it requires more work, and sometimes expert help is indispensable, just like with everything else!

Does this mean I need to sleep train at a certain age?

No. Sleep training is a way to change behavior if your child is not getting the sleep they need, or to help your child sleep better without needing habits you may find problematic to your own sleep as well as theirs (for example, needing to bounce them on a yoga ball over and over throughout the night, being awake hours each night causing you both to lose necessary sleep). If you are being safe regarding sleep, and are happy with the amount of sleep you and your child are getting, you are fine! That may change sometime in the future, and that’s fine too!

So there you have it- I hope this helps you to feel more informed about what aspects of child sleep are up to development, and helps you to feel confident in implementing behavioral strategies if it’s the right time for your family!


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I’m Katelyn,
Award-winning pediatric sleep consultant, child development expert, and most importantly, wife and mom.
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