Infant sleep deep dive
An addition to Parenting Translator's Sleep Training Deep Dive, incorporating a wider view on all things sleep
I’m really passionate about the area of infant sleep. Consequently, this article is really long. To read all of it, click the ‘read in app’ or ‘read online’ buttons.
Dr Cara Goodwin of the Parenting Translator newsletter recently wrote an article doing a deep dive into sleep training research. It was thoroughly researched and highly practical, and if you’re considering sleep training, I highly recommend that you read the full article, which I will link to at the bottom of this article.
To summarise, these are the questions addressed in the article, and a very brief summary of the answers:
Does sleep training improve infant sleep?
Sleep training may result in modest improvements in parent-reported sleep for children over 6 months old and may increase the length of the first stretch of sleep by about 15 minutes. However, these improvements are temporary, and sleep training does not guarantee that your child will be a good sleeper as they grow from infant to toddler and pre-schooler.
What about sleep training for infants under 6 months?
There is no evidence that any type of sleep intervention improves the sleep of young infants.
Does sleep training cause stress for infants?
The research is limited in this area, and we cannot yet conclusively say whether sleep training has a negative impact on infant’s cortisol levels.
Does sleep training have long-term negative impacts?
There is no evidence that sleep training results in long-term negative impacts, however the studies looking at long-term effects are all seriously limited which makes it impossible to form a definite conclusion.
Does sleep training improve parent mental health?
Sleep training may reduce symptoms of maternal depression, however, it is unclear if it is the sleep training or the personalised support that is providing the most impact.
An even deeper dive into infant sleep
While this article is the most thorough and unbiased article I’ve read regarding sleep training, I have a big problem with it. It does exactly what it says on the box – it is a deep dive on infant sleep training. However, I believe that if we’re talking about sleep training, it pays to situate the research within the wider realm of what our social expectations are around sleep, and the biological and evolutionary norms for sleep.
Sleep training is the dominant narrative in our society around infant sleep. In her article, Dr Cara Goodwin points out that two-thirds of parenting books advise parents to sleep train. Additionally, one study of over 2000 participants found that 64% of parents reported implementing a behavioural sleep intervention. There is also the pressure that most parents experience when it comes to considering infant sleep, with the question “does he/she sleep well?” coming just as frequently as “are they a good baby?”.
From my own interviews with new mothers, many report feeling pressured from every angle to sleep train. For example, one mother described it like this:
“I had felt the pressure to try it [sleep training], because people were kind of like talking about that as though it was an inevitable outcome. You would have to do that, because that's the only way they'll learn to sleep.”
And another said:
“The idea was that you're going to ruin your kid somehow if you don't get them to sleep [through sleep training]. The narrative is that it's going to make it really difficult for you down the track and that you're going to regret not teaching them. And I worried that I was doing something wrong.”
When we only talk about infant sleep through the narrative of sleep training, we risk causing unnecessary anxiety and stress on the many families who find that sleep training doesn’t work for them or align with their values. They may be left feeling as though any problems with their infant’s sleep are due to their own inability to train their child to sleep. It also leads many parents to fear that they have failed when, following sleep training, the improvements that they did notice in their baby’s sleep don’t last as long as they were led to believe they would.
So how did we get to the point where sleep training became the dominant narrative?
There isn’t just one factor that we can point to as the root cause of sleep training’s dominance. Instead, it’s a multitude of broad level societal changes that have occurred over the last 200 years which have entangled themselves together in such a way that our relationship with sleep has profoundly changed. Here’s my attempt at disentangling some of these factors:
Moving away from communal sleep spaces
For most of human history, sleeping together wasn’t just the norm, it was a necessity. When beds were little more than a thin strip of fabric on the ground, sleeping in close contact with others provided needed warmth. It wasn’t until the Victorian era that the upper classes starting routinely bisecting their houses and providing every family member with their own room. Within a few decades, the ideal of solitary sleep had spread throughout Europe and North America, providing privacy and a sense of moral superiority.
Advent of electric lights
In addition to sleeping communally, for thousands of years people went to bed when it was dark and got up when it got light. While they may have been in bed for 10 or more hours, they weren’t asleep the whole time, and they didn’t expect to be. As well as experiencing a fair amount of time in bed before the onset of sleep (which differs dramatically compared to the 15 minute sleep onset we now experience), they also predominantly experienced bi-phasic sleep. In between the two major sleep intervals, they had an hour or more of quiet wakefulness. However, with the introduction of electric lighting about 150 years ago, came the opportunity to stay up later. This resulted in compressed sleep, making it abnormal to be awake in bed.
Pathologising sleep
Not only is being awake during the night now considered abnormal, in many instances we’ve now pathologized it. We label it insomnia and prescribe pills to treat it. In many ways, the hustle culture that we live in contributes to this even further as it suggests that it is unproductive to be in bed and not sleeping, so we feel pressured to idealise our sleep.
Emphasis on independence
Our culture also impacts sleep by over-focusing on the ideal of independence. With the rise of Behaviourism (an early branch of psychology that emphasised the idea that all behaviour is conditioned through interactions with the environment) came the idea that solitary infant sleep should be enforced so as to avoid coddling the child. Some influential parenting experts of the time even went so far as to claim that responding to an infant’s cries was akin to sowing the seeds of communism. According to behaviourist principles, an infant could be trained to sleep though the night by repeatedly ignoring their instinct to cry out when alone.
Unrealistic expectations of infant sleep
During the 1950s and 1960s when sleep researchers first started quantifying infant sleep, breastfeeding rates were at an all-time low. The vast majority of infants left the hospital relying on formula as their only source of nutrition. The problem with current sleep recommendations and expectations is that they are largely based on the infants studied in this time period. There are significant differences in sleep patterns between breastfed and formula fed infants, as formula is more difficult to digest, causing formula fed infants to sleep longer at an earlier age. Expecting a breastfed infant to consolidate sleep into the 4+ hour chunks that a formula fed infant is capable of is unrealistic given the easily digestible nature of breastmilk, particularly in the first few months.
Capitalist elements
There are also capitalist undertones behind sleep training. A baby who has their own sleep space requires a cot, bedding, white noise machine, special night lights, soft toys with an internal heartbeat mechanism, sleep suits, and more. Advertising and social media influencers push the need to buy all these things, each claiming that this product will solve your baby’s sleep problems and guarantee that they will sleep through the night. Additionally, there is also the rise of the infant sleep coach, who would be out of a job if parents embraced biologically normal infant sleep. To maximise profits, the sleep training industry (which is valued at least at $325 million globally) needs people to believe that an infant waking through the night is a problem to be solved.
The overall trend
Our understanding of and relationship to sleep has warped dramatically over the last 200 years. Where we once slept communally and expected night wakings for both adults and infants, we now expect to sleep undisturbed and solitary. This has led to, in my opinion, unrealistic expectations of what normal infant sleep should look like and has pushed many parents to accept sleep training as the only option.
Sleep training is a profoundly modern, Western notion
When we situate sleep training amid the broader framework of biologically and evolutionarily normal sleep, we better understand that sleep training shouldn’t be the dominant narrative. In fact, most research on sleep, and indeed, most psychological research in general, has been conducted on a narrow subset of participants – those from Western, educated, industrialised, rich, democratic (WEIRD) nations. By over-relying on these research findings, we risk generalising conclusions to populations which differ dramatically.
For example, in Australia, the US, and other WEIRD countries, we typically come at infant sleep research from the perspective that co-sleeping and night waking are undesirable. However, when we look at cross-cultural research, we see that co-sleeping is considered common throughout many other countries. In Brazil, 45% of children co-sleep at 12 months. In China, 37.6% of school aged children were still sharing a bed, and in India the number of co-sleeping school children is even higher at 93%. Clearly not all cultures consider sleep training as a necessary step in teaching children how to sleep.
“If anthropological evidence on infant sleep and development were integrated and used as a starting point to inform infant sleep research, there is no doubt that the question we would be asking is not if it is safe for an infant to sleep next to its breast feeding mother, but rather, is it safe not to!”
-Dr James McKenna
Co-sleeping as the dominant narrative
Given everything that we’ve discussed, we need to understand that an infant waking during the night and expecting physical closeness or another feed isn’t the big problem that our societal conditioning has led us to believe it is. Indeed, the question should be less “should I sleep train?”, and more “should I provide my child with the sleep environment that they are evolutionarily and biologically primed to expect through co-sleeping?”. Let’s answer the same questions as in the original article, but this time asking them about co-sleeping. To clarify, co-sleeping can mean many things, from sleeping together in the same room, to accidentally falling asleep together on a couch (which is not considered a safe form of co-sleeping), to sleeping together on the same prepared sleep surface. For the purpose of this review, co-sleeping will refer exclusively (unless stated otherwise) to sleeping together on the same sleep surface, prepared for safe bedsharing.
Does co-sleeping improve infant sleep?
Co-sleeping is associated with increased infant/maternal night interactions, increased overnight breastfeeding, increased movement overnight, and increased awakenings compared to solitary sleep. By those metrics, co-sleeping doesn’t work.
However, co-sleeping results in reduced overall wake times for both mother and infant, resulting in more total sleep. It seems likely that the increased proximity inherent in co-sleeping means that parents are more aware of night wakefulness, yet by the same token they are also able to respond to the wakefulness quickly, enabling everyone to return to sleep swiftly.
It should also be noted that there appears to be some difference between intentional co-sleepers (those who choose to sleep with their child because they believe that it is the best arrangement for them), and reactive co-sleepers (those who prefer to sleep separately, but who are sleeping with their child because their child won’t sleep well alone). In this study, both intentional and reactive co-sleepers reported similar levels of potentially problematic sleep behaviour, which were significantly higher than those reported by parents of solitary sleepers. However, when these behaviours were weighted by parental judgement, the scores for intentional co-sleepers dropped substantially, to the point that they were equivalent to those of the solitary sleeping group. It appears that intentional co-sleepers are observing these potentially problematic sleep behaviours, yet do not consider these behaviours inconvenient or troubling.
What about co-sleeping for infants under 6 months?
Co-sleeping may be particularly beneficial for younger infants, and newborns in particular. Co-sleeping helps babies regulate their temperature, breathing, and heart rate. Co-sleeping also facilitates the breastfeeding relationship, with this study from Professor Helen Ball indicating that mothers who initially want to breastfeed can generally handle the sleep disruption of breastfeeding without bed-sharing for only 6 weeks before turning to other alternatives. She also found that almost all mothers who breastfed beyond 8 weeks incorporated co-sleeping into their sleep routine.
The combination of breastfeeding and planned co-sleeping may also reduce the possibility of SIDS and suffocation. It has been found that breastfeeding mothers automatically assume a protective position when sleeping with their infant - facing towards her infant with her knees drawn up under the baby’s feet and her arm positioned above the baby’s head. This position both facilitates breastfeeding (which in itself is a protective factor for SIDS risk), but also ensures that the baby can’t slip below the blankets or wiggle towards the pillows. Finally, although it is impossible to state causality, it should be noted that a large international survey indicated that cultures with the highest rates of bedsharing often had the lowest rates of SIDS.
Does co-sleeping cause stress for infants?
There is one study that I am aware of that examined infant cortisol levels and examined the association between these cortisol levels and night-time parenting practices. This study indicates that co-sleeping was associated with an increase in cortisol levels at the end of bedtime. However, given that this study was conducted on a sample where co-sleeping was not normative, these results should be interpreted with caution. On one hand, it is possible that co-sleeping predicts less optimal cortisol patterning. However, it is also possible that the increase in cortisol reflects greater familial stress that has been shown to accompany extended co-sleeping in cultures where co-sleeping is less socially accepted.
On the contrary, there are also studies which showed that infants who predominantly co-slept showed less cortisol reactivity to mild stressors at 5 weeks, 12 months of age, and between 3 to 8 years of age. It appears that the greater physical contact with parents inherent in co-sleeping provides more opportunities for parental co-regulation, which influences the functioning of the physiological stress system.
Does co-sleeping cause long-term negative impacts?
A meta-analysis of 15 cross-sectional studies found some evidence that co-sleeping was related to several sleep disturbances in childhood. However, these studies did not control for reactive bed-sharing (which is where co-sleeping occurs as a parental response to existing sleep problems). Consequently, some co-sleeping may be reflective of pre-existing sleep disturbances, rather than being the cause of them.
There are a handful of longitudinal studies examining long term effects of co-sleeping. One longitudinal study of preschoolers found that while intentional co-sleeping children took longer to fall asleep independently and sleep through the night than their solitary sleeping counterparts, the intentional co-sleeping children were also more likely to be self-reliant and exhibited more social independence. Another study examined the link between early room-sharing and behaviour at between 6-8 years of age and found that there was no link between early room-sharing and sleep or behaviour problems. On the contrary, increased weeks of room-sharing in the first 6 months was predictive of more prosocial behaviour in middle childhood. Finally, this 18 year study tracking infants to adulthood found no negative impacts of bedsharing. On the other hand, there is some evidence demonstrating positive psychological benefits of early co-sleeping on self-esteem and overall life satisfaction.
Does co-sleeping improve parent mental health?
There appears to be a bi-directional link between perception of sleep problems and maternal depression. Perception of sleep problems contributes to shortened maternal sleep, which contributes to depressive symptoms, as described here. Conversely, experiencing depressive symptoms is predictive of a mother describing her infant’s sleep as problematic, as described here.
Given what we have discussed above about the variability in labelling infant sleep as problematic by whether co-sleeping was intentional or reactive, this study which examined the consistency of sleeping arrangements may be particularly relevant. They found that with an increase in hours spent co-sleeping came a reduction in maternal depressive symptoms. They also found that both habitual co-sleepers and non-co-sleepers had an increased quality of mother-infant interaction compared to inconsistent co-sleepers. Another study found that co-sleeping was only associated with a decrease in marital satisfaction when it was reactive as opposed to intentional.
On the whole, it appears that only reactive co-sleeping is associated with decreases in maternal mental health and marital satisfaction.
How do I co-sleep?
If you’ve decided that co-sleeping is something you want to try, you need to know that it’s not as simple as bringing your newborn into bed with you. Our modern sleeping surfaces were not designed with co-sleeping in mind. Fortunately, there are simple steps you can take to ensure that your bed is a safe sleep surface. Ensure that there are no extra pillows, stuffed animals, or infant sleep positioners in the bed (your own pillow is fine). Remove heavy blankets. Make sure there are no cords in the sleeping area. Make sure that your mattress is firm enough that your baby doesn’t get stuck rolling towards you. Be mindful of cracks where baby can get stuck (such as between the mattress and the wall), and of the fall height from the bed to the floor. You may choose to move your mattress to the floor or attach a sidecar cot. More information about the Safe Sleep Seven can be found at La Leche League International.
What about if co-sleeping isn’t for me?
Hopefully, this article has helped you realise that it is possible to reject modern cultural expectations and return to a biologically and evolutionarily supported sleeping arrangement without negative impacts.
However, I also acknowledge that co-sleeping isn’t right for everyone. It does need to be stated that unsafe co-sleeping and bed-sharing can increase the risk of SIDS and suffocation. For these reasons, if the parents are smokers, go to bed with alcohol in their systems, or take medications that cause drowsiness, co-sleeping should be avoided. Additionally, if the baby is premature or has chronic illnesses, they are already at an increased risk of SIDS, so co-sleeping should be delayed until the baby is healthy and full-term. Finally, formula-feeding doubles the risk of SIDS, and as formula-feeding mothers do not assume the natural protective curl around their infants in the same way as breastfeeding mothers, the baby is at a higher risk of moving upwards towards pillows or down under the bedding. However, there is evidence that from 4 months of age, bed-sharing no longer significantly contributes to the risk of SIDS (as long as the parents are not smoking).
There are plenty of other reasons that may contribute to you not feeling comfortable with co-sleeping, anything from work arrangements to family pressures. And that’s ok. There are still plenty of other things beside co-sleeping that you can do to reduce the impact of sleep problem perception.
1. Get more information about what developmentally appropriate expectations for infant sleep are.
Due to the aforementioned pioneering sleep research on formula fed infants, the expectations around infant sleep that many of us have will only lead to frustration. In general, babies (but particularly breastfed babies) will wake up more times through the night than you would expect, and will take longer to “sleep through the night” than you would expect. This is normal. In fact, an informal poll of almost 10 000 people by Lucy Webber (IBCLC) indicated that 91% of 4-6 month old babies wake through the night, 93% of 9-12 month old babies wake through the night, and even 71% of 3-4 year old children still wake through the night. Night waking is normal!
In general, many people find that simply having a better understanding of what is developmentally appropriate helps. It allows us to shift our perception from “my child is still not sleeping through the night and that is a problem” to “my child is not sleeping through the night and that is normal and to be expected”.
2. Embrace “bad habits”.
Feeding to sleep, rocking to sleep, and cuddling to sleep are only a problem if they’re a problem for you. If you find that it works, that’s fantastic! There is plenty of evidence showing that breastmilk contains sleep-inducing hormones, which can make breastfeeding a really simple way to get your baby off to sleep. And many parents enjoy the reconnecting quiet time snuggled with their toddler or preschooler at the end of a day. Ignore what anyone else says about these being bad habits that you need to break. Your child will eventually outgrow the need for your constant presence at night. As Pinky McKay (IBCLC) says “if your child does still like to snuggle up to a breast when he’s twenty one – you can be sure it won’t be yours!”
It’s also worth noting that when we are told that we need to stop breastfeeding and rocking to sleep, we are often told to instead use sleep aids that can be even more inconvenient. For example, many sleep training books suggest that the room needs to be dark, that there should be a white noise machine, that baby should be in a special sleeping bag, and that you should be following the same routines before every nap and bedtime. Unfortunately, this can create nap anxiety for parents, as they feel the need to structure their whole routines around making it home for naptime.
“Bad habits” can simplify things for parents, in that they can know that their baby will fall asleep anytime, anywhere, without a structured sleep environment.
3. Sleep train.
I’m really not going to go into it too much. Personally, I believe that sleep training should be seen as a last resort choice, and the fact that so many families feel pressured to engage in it in the first few months of their children’s lives is symptomatic of the lack of support they are provided with, as well as the prevalence of unrealistic expectations around infant sleep. This is not to shame those who choose to sleep train. As discussed in the Parenting Translator article and touched on at the start of this article, there doesn’t seem to be any long lasting negative consequences of sleep training, and sleep training may offer some improvements to infant sleep and maternal mental health. While some opponents to sleep training argue that it can damage the attachment relationship and cause infant trauma, I believe that any outcomes depend more on the general trend rather than individual decisions. If sleep training occurs, but is embedded in a relationship of otherwise responsive and respectful parenting choices, any potential negative outcomes to the attachment relationship will be tempered. However, to restate my position, I believe that sleep training is generally unnecessary, and that the sleep problems that often cause parents to believe that sleep training is needed are no longer problematic when viewed through the lens of evolutionary and developmentally appropriate infant sleep expectations. If you want more information on sleep training, I highly recommend that you read the Parenting Translator article linked below.
Conclusion
We know that sleep training offers only modest improvements in sleep, and that these improvements are not long lasting. We don’t know if it causes long term harm. We do know that babies don’t like being sleep trained. We do know that many parents feel pressured to sleep train, as though it is the only option.
On the other hand, we also know that co-sleeping and responsive nighttime parenting reduces overall wake duration overnight for both parents and infants. We know that co-sleeping offers long term benefits. We know that co-sleeping promotes breastfeeding and can reduce the risk of SIDS. We know that being intentional about co-sleeping reduces the likelihood of viewing sleep disturbances as being problematic. And finally, we know that co-sleeping is biologically, evolutionarily, and cross-culturally normal.
There’s no right decision here. I’m simply presenting facts. Ultimately, it’s up to you to decide what you feel most comfortable with, and what you think will work best for you and your family.
I'd love to hear your thoughts! Have you ever felt pressured to avoid co-sleeping? Or maybe that your infant wanting your presence overnight was problematic? Adding to the conversation helps us all.
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This was really validating, thank you.
Thank you for calling this newsletter. It was important to me to do a thorough review of the research. You readers can find a direct link to the sleep newsletter here: https://open.substack.com/pub/parentingtranslator/p/sleep-training-deep-dive?r=kczpl&utm_medium=ios&utm_campaign=post