I have the benefit ( I say this loosely lol) of being half zimbabwean and half american. I was raised born and raised in southern Africa and moved to the US for college and subsequently had babies. It AMAZES me at the lack of connection the west has to matrescence. My partner and I were told we were "ruining" our kids for holding them and wearing them as well as breastfeeding past 1. I remember after giving birth the nurse insisted they sleep ABC " Alone, on their back, in a crib" . After one night of poor sleep constantly waking up to nurse my baby I said to hell with that and did what I had seen all my aunt, cousins, and sisters doing as a kid. Co-sleeping, babywearing are the basis of how we protect and take care of our offspring.
It's because Americans (and any place where the mother needs to work relatively quickly after birth) need to be able to sleep through the whole night (ish) and the baby crying wakes you up.
Yeah, well it's effective at making sure the parents sleep through the night and can perform effectively at work so they don't get fired and be unable to feed their kid
I developed chronic insomnia post partum. I would sleep less than 4 hours a night and was slowly losing my mind, health and happiness. I tried medication, supplements, sleep hygiene - everything. My daughter was getting up 3-5 times a night and would want to play for hours. Eventually my husband ended up handling almost all wake ups in an attempt to help me get out of the insomnia cycle. We were all exhausted. We ended up doing Taking Cara Babies - the gentle approach to sleep training when she was a year old. Within 2 nights she was trained. My heart hurt for her little cries those 2 nights, but my entire family’s health improved. She was and continues to be a very happy and congenial toddler and feel we are very close. For me, I wish I had done it sooner. I agree we need more research, but my biggest takeaway is that we should listen to our mother instincts! My opinion is some babies and moms may benefit from it - others may not.
I also developed insomnia postpartum. It was absolute hell. I did the newborn Taking Cara Babies program and never needed any sleep training beyond that (baby still woke through the night until 7 months, but it was typically once by then, maybe twice). And thank god I did because I absolutely could not have handled multiple long term night wakes in addition to the fact that my body just refused to shut down and sleep. So sorry you had to deal with that - it was one worst, most lonely times in my life.
I'm almost of the mind we don't really need research on this. We need support for parents and longer parental leaves so this issue doesn't become such a tortuous pressure-cooker. With how much kids grow and change in the early years, I really can't see how sleep training or not would be such a major factor versus the literally thousands of moments we spend nurturing, cuddling, assuring, holding boundaries and teaching skills. It just feels like another way to shame moms for choosing "wrong" or not.
Insomnia is awful, and I've struggled with it both in pregnancy and postpartum. I have found different methods to deal with it as I personally cannot cope with listening to a baby cry for extended periods. Also I don't really blame my babies for my insomnia, their wake ups certainly don't help but there are many nights when they're lying next to me sleeping peacefully while I stare at the ceiling.
Everything about childrearing is so emotive and it's hard not to feel defensive about choices made. There are many things I wish I had done differently with my firstborn based on what I know now. Our culture and society can make it really hard to follow what our babies expect from an evolutionary perspective, but that means we should be trying to change culture and society, not trying to change the babies.
I’m a SAHM to twins and I wish I had done sleep training even earlier. Sleep deprivation is torture and one bad night of crying is worth the peace that we have now. If moms want to co sleep and get up 6 times a night with their baby, that’s awesome! But I don’t
Technically I didn't have to "get up" 6 times a night as my baby was right next to me. Most of the time he would stir slightly and while laying down half asleep I'd nurse him and then continue sleeping. When we cosleep our sleep cycles (amongst other things) sync up which helps moms feel more rested. I think sleep deprivation sounds awful but I don't think training our babies not to cry for us is the only solution to the situation.
My experience currently! It was really hard when the 4 month regression hit, but then we started cosleeping (we are at 7 months now with every 90 min wake ups still) and maybe a few weeks in something clicked and the sleep cycles aligned and I’m rested and thriving. If someone would’ve told me I’d “wake up” every 90 minutes for 3+ months straight and still feel great I would’ve been SHOCKED. But it somehow works 🤷 happy I didn’t give up on it.
What I did give up on was trying to control his sleep and not being stressed about it takes a weight off.
I wish that had been my experience! After trying cosleeping (which did not help and increased wakeups for us) and 10 months of going back to working full time on no sleep, I couldn’t continue once she hit a year old. I really appreciated the Taking Cara Babies approach.
yeah I think across the board co sleeping increases wake ups -- had that too but again just the half asleep thing. apparently there's some evolutionary biological reason why the waking up more is beneficial. easier to say when you're not trying to balance that with modern life.
I was severely sleep deprived with my third who didn't sleep, on top of insomnia. The Taking Cara Babies program did nothing, I even hired a sleep consultant. He just didn't sleep until he got older. Co-sleeping was the only way to survive, and the nights of CIO were just torture on top of everything. Just adding this in for the moms reading here who want to just cry when they hear "I did such-and-such sleeping program" because it's not working. I had to delete some acquaintances who only had one baby and were claiming success with Cara lol, my mental health was so bad. He's 5 now, I eventually slept again.
I hear you - it is hard to describe how you feel after 10+ months of totally inadequate sleep, but it is definitely a form of torture. Each morning I commuted to work I would repeatedly slap myself in the face to stay awake - it felt ridiculous (because it was). It just wasn't workable for my situation.
I appreciate your writing - I found you through your pieces critiquing Erika Kosimar - but I think you are committing a few mistakes here.
First is your suspicion that if evolution and science don't match, the problem must be in the science. Evolution can provide a hypothesis - for example, that sleep training may cause developmental mental health issues - but science isn't obligated to confirm this hypothesis. It's possible that we evolved to cosleep AND that not cosleeping doesn't cause long-term harm. So to me, your claim sounds like a form of the appeal to nature fallacy - that only what we evolved to do is good and right, and the science is sus if it doesn't match it.
Second, I think the sentence "We have no idea if what I did to my son is okay, and I will forever be asking questions" is open ended and can make parents more anxious than they already are. Part of why I appreciate the work Emily Oster is that she helps lower concerns that lead anxious parents into thinking each and every one of our actions may cause long-term damage. IMO, kids are flexible, and being anxious about our every misstep may affect their mental health in other unintended ways.
All this said, I really do appreciate you critiquing the research in this piece. I just think it could benefit from tightening some of the claims around evolution, and steering clear of the fear-based claims that play into the culture war around sleep training. I hope this is helpful!
I really appreciated "Sweet Sleep" by La Leche League, that reviewed research on sleep training and co-sleeping. They mentioned in the book that research showed that sleep trained infants did not get better sleep, they were just quiet, but that they had as many wake ups as prior to "sleep training", and that their salivary cortisol was elevated at night even though they didn't cry out. I never went to the primary sources, because who has time for that, but I found that book useful for the other side of the research.
Came here to say this too - the data on infant wake-ups is very limited as it only takes into account any wake-ups that the parents report. Considering sleep training essentially teaches the infant not to signal to the parents during sleeping hours it’s pretty easy to see the limitations there!
It’s amazing that 100% of mothers don’t have depression in the US with the whole breastfeed but no cosleeping message! I’d also like to see exploration of the role of Back to Sleep on rates of maternal depression. Babies don’t sleep well on their backs in many cases.
I don't think this essay handles the "evolutionary evidence" around co-sleeping appropriately.
Our Hunter-gatherer ancestors also didn't use vaccines, and the clear pain-avoidance response shown by children and their parents could be taken as a clear "evolutionary evidence" that vaccines cause harm. As a science writer, I hope you can spot the fallacy here. Evolutionary impulse knows nothing about vaccines, and therefore should make zero contribution to our priors.
Nikhil Chaudhary handles the evolutionary role of co-sleeping appropriately - it indicates that in a hunter-gather environment, co-sleep is an effective way to shelter infants from the elements and predation. Given that we already know that infants in temperature controls homes away from predators are not in physical danger, we know the evolutionarily ingrained behaviors simply do not apply here. And since there is no evolutionary selection on the quality of infant or maternal sleep, we also know that evolution has nothing to say about this.
The danger of co-sleeping on the other hand, in terms of possibly suffocating infants, is real and documented in the modern environment. Since you read Oster, you know that this risk while real is somewhat overstated and may be driven primarily by parents sleeping on couches and/or in a state of intoxication. Of course those things also don't exist in a state of nature either.
If you want to co-sleep despite an absence of specific scientific support you are certainly welcome to do so. Oster frequently makes this point, that nothing in the consideration of science takes away the importance of individual agency in parenting.
But please don't mistake "your idea of what is natural" for "scientific evidence".
Ah yes, Jeff, thank you for bravely stepping in to compare co-sleeping with vaccines, the rhetorical equivalent of comparing a campfire to a centrifuge.
The idea that evolution “has nothing to say” about infant-maternal sleep because there wasn’t a randomized control trial conducted in the Pleistocene is, let’s just say, adorably reductive. Of course, evolution didn’t engineer for blackout curtains and memory foam mattresses; it engineered for survival, which just so happened to favor the babies who stayed close to their parents and didn’t freeze to death or get eaten by leopards. To suggest that those survival strategies are now entirely obsolete because we invented thermostats is like saying hunger cues no longer matter because we have Uber Eats.
You cite Nikhil Chaudhary approvingly, but then you declare that since evolution didn’t select for maternal sleep quality, it must be irrelevant, as if sleep deprivation hasn’t been shown to degrade maternal responsiveness, lactation, and mental health, all of which very much do affect infant survival and maternal fitness. Evolution, it turns out, isn’t as narrowly blinkered as your argument.
This whole “your idea of what is natural isn’t scientific evidence” line is a straw man. Nobody is saying natural equals good, full stop. The point is that an evolutionary lens informs scientific hypotheses; it doesn’t replace evidence, it helps frame it.
So yes, Jeff, we agree: don’t mistake instinct for proof. But also don’t mistake pedantic contrarianism for clarity. The science here is evolving. kind of like our species. Try to keep up.
OP says "I believe the evolutionary science behind co-sleeping (and maternal responsiveness to crying) is so compelling that we would need many, replicated, high-quality studies in order for me to be convinced that it’s totally safe and has no negative effects on children or mothers." This is not framing evidence, this is replacing evidence.
I think the unintuitive safety of vaccines is a compelling example, but there are a lot "evolutionary instincts" which are maladaptive today. Eating sweets is a evolutionary impulse - It's clearly telling us "something" that the body wants to eat sweets, but it's not a good prior for optimal nutrition.
I don't know anyone making an evolutionary argument in favor of sweets, but in fact you will find a lot of bad takes on the Internet that come from the supposed wisdom of our evolutionary instincts. I don't wish to take those on as priors, actually.
We're supposed to be taking parenting tips from the ancestral past, but we're talking about a time and place with an infant mortality rate was x10 higher than what we have today. Its no leap to say the driving considerations behind infant health in that environment are just vastly different - as different as eating sweets in a cafeteria is from scarfing wild fruit before a long winter.
If you are saying we should follow available scientific evidence from modern environment, and disregard the biases going into that, I can agree with you there.
I don’t think the evidence in favor of sleep training is at all comparable to the evidence for the efficacy and safety of vaccines. We have a strong drive to avoid puncture wounds and introduction of foreign substances to the body. An organism lacking this drive cannot survive long.
However, we also have plenty of evidence to update on this prior: in the specific case of properly developed vaccines, injection is not dangerous and in fact salutary. And the downside risk of being unvaccinated can be serious. This does not mean the drive to avoid wounds and foreign substances is completely upended!
Likewise, we have a strong drive, shared with all primates, to maintain close physical content throughout infancy. Is this drive causing some harm? Does the intervention of sleep training have some benefit comparable to vaccines? It seems to me that we have 1/100,000th of the evidence compared to vaccination, for a much less well defined problem and benefit. There’s also a good amount of evidence that withholding physical touch and reassurance can have catastrophic effects at high “doses” (Romanian orphanages, Harlow’s “wire mother” experiments, still face experiment, etc)
It could well be that these effects are non linear, and don’t appear until you reach a certain threshold of withholding. But letting a baby cry it out night after night seems like a significant dose.
The point is that there *is* no scientific evidence, in essence, on this question. The RCT discussed is self evidently almost entirely worthless, except to rule out that either sleep training or not sleep training will cause overwhelmingly massive long term harm. The evolutionary evidence is that some 99.99% of all human babies that have ever been born have co-slept with their mothers, and there is literally no evidence that this is actually harmful outside of other kinds of pathological modern situations. If you can’t see this is an obvious slam dunk for trusting the prior over the one mediocre piece of science, well…I’m praying for you.
There actually is scientific evidence that it co-sleeping poses a rare risk of accidental suffocation of infants. This is why the AAP and NHS advice against it.
OP doesn't address this. Instead she analyzes the studies saying there are no downsides of sleep training, and concludes those studies aren't good enough. And on that basis, that is without any supporting experimental evidence, decides sleep training must be harmful or risky for the well-being of children in a way not detected by studies.
Would be better for OP to just say she's chancing the (rare) risk of suffocation because co-sleeping brings the family comfort and joy, which is an entirely legitimate choice for a parent to make.
There's not, though; that's what all the discussion of scientists failing to distinguish between different details of the context of co-sleeping is about. There's no study suggestion that co-sleeping supine with a breast-feeding mother, without a pillow or excess linens, etc, is any suffocation risk whatsoever.
Breastsleeping does more than protect infants from the elements and predation. It confers protection from SIDS, facilitates extended breastfeeding, and improves sleep quality for mothers.
I know right! my first woke up crying evert 15 min even when I was next to him and boob was available. It wasn't until I sleep trained him at 6 months that we all got some sleep and he started waking up only at 6am, which was clearly hunger after 10h of sleep and so I breastfed him.
Thank you for this extremely nuanced article! As a FTM, I was terrified of SIDS and so I got TCB's newborn course and followed everything she said to a T, minus the whole drowsy but awake, don't nurse to sleep BS (does that work for anyone??). My daughter was sleeping 12 hours by 12 weeks alone in her crib. I congratulated myself for following the rules and having a wonderful sleeper. And then around 8 months, she started teething, she got a couple ear infections, and her separation anxiety kicked into high gear. I tried letting her cry but caved after five minutes when I could tell she was truly panicking. And then I read Sweet Sleep (LLL) and Dr. James McKenna's book, memorized the Safe Sleep Seven, and taught us both how to safely breastsleep and bedshare. Total gamechanger. I was sleeping better than I had since before I got pregnant - having her next to me, once I got used to it and stopped holding myself rigidly in place out of fear of crushing her to death, was SO much more restful than waking up 20 times a night to stare at the monitor glaring in my face to make sure she was breathing. We always started her out in her own bed and brought her to our bed after her first wake, but I continued bedsharing with her through weaning at 22 months old, up until she randomly started sleeping through the night in her own bed of her own accord at 2.5 years old. Which was great timing because I was newly pregnant with my son, whom I have bedshared with since birth (he is almost 8 months old). This time around it was a total no-brainer. He can sleep with me as long as he needs to. I feel like I get really good sleep even though he nurses about every two hours around the clock, and I love having him right there with me. Trying to do it any other way feels like such a waste of energy and precious time with my baby. I work outside the home full-time, so maybe I'd feel differently if I didn't, but for us, for now, it's the perfect fit.
I think the most fascinating thing for me was before when i worried about putting my newborn in the crib i would wake and panic searching for her in the sheets.
As soon as i said to hell with it and let her sleep next to me they vanished. Instantly vanished.
I’m not sure what that says about bedsharing but it sure is interesting.
Also, thank you for putting into words the way i felt reading that study, and most, sleep training studies. I just ended up feeling very…not reassured.
Every mother I've ever spoken to reports the same--waking up in deep confusion trying to find where the baby is in the bed. Every bedsharing mother I've spoken to reports it went away when they started bedsharing.
Before I started bedsharing with my first, I would wake in a panic saying, “Baby, baby” and looking for her frantically. My subconscious could not reconcile her being any distance from me during sleep. So fascinating!
My parent and their ancestors are from a “family bed” culture (there’s a special word for the bed that everyone in the entire household sleeps on together, for them it was 7 people) and they disliked their experience so much they were determined to rise above poverty and eventually buy a house where every kid had their own room with a door that closed. So I have observed the maternal instinct can go either direction. I feel like the family bed concept is romanticised by affluent westerners, and also taken out of context with other cultural practices. I don’t think the benefits translate directly to us in the west, as in my heritage culture, the bed sharing pairs with other aspects such as waking with the sun/going to sleep at sunset (much harder to go to sleep with your baby when the sun sets at 4:30pm in the winter in the US when your job ends at 5pm), postpartum rest (where the mother recovers at home for 1 month while female relatives come over and take care of the house and chores AND baby), infant pottying (it’s useful to sleep with baby when you don’t have a laundry machine or diapers, so you can potty them when they wake in the middle of the night. turns out a lot of babies wake and cry because they need to pee!), and filial piety + anti-individualism + corporal discipline (I have observed the kids in the US to overall have a way different relationship with their parents). My parents worshiped their ancestors and had the winter months as holiday, we americans worship work productivity and never rest. The benefits of sleep practices from one doesn’t feel like a useful point of comparison to the other.
Very interesting analysis! I am very swayed by your argument that everyone used to
Co sleep. Here in Austria, das familienbett “family bed” is very common. Several friends removed all wardrobes and furniture to create a 3 meter wide bed to accommodate all family members. At the hospital where I gave birth, midwives encouraged me to sleep with my newborn in the hospital bed. On the other side , it’s weird because I haven’t seen a single doctor promoting co sleeping on social media. For example, I follow @thatsleepdoc on instagram and he’s very adamant that sleep Training is better for parents- helps them be more responsive, get better sleep, and feel less frustration and there are no long term consequences for kids. Granted, he’s in the USA, speaking to an American audience who needs to go back to work and truly cannot cope with months of poor sleep.
American infant advice is so faulty that when my husband and I brought our newborn first baby home, we were absolutely shocked that she didn't want to sleep alone in the flat, hard, cold bassinet we'd procured for her. We did do minimal sleep training with her, but it was hell. I still sleep with our second who is nearly two and breastfeed her 2-3 times a night and I still get so much more sleep than I did with my first!
One of my twins (fraternal) stopped waking up after 3 nights, and the other NEVER stopped crying and never stopped needing to be near me at night for years until he was 6 or 7. Individual differences might be key here. Sleep training can work for some kids but not all.
The son, E., who needed to be near me at night, at age 3 or 4, would every night come into my room (very close by, where I slept in a double bed with my husband). I eventually put down a mat right by my side of the bed, and E would just lie down on the mat and sleep. My husband was fine with that and E didn't try to get up in bed with me. But E also required that I lay down with him to fall asleep each night, which I did. But this was difficult since I would sometimes fall asleep there, it would take a long time, and so that would occupy my evening. My husband got mad and decided we just needed to try 'cry it out' one more time,no more coddling. So my husband commandeered the situation and basically was there with E in a hammer lock head hold while E cried and flailed and protested and I kept away in a separate room. E cried for hours, and my husband was determined to keep E from running to Mommy. E did not stop crying. Finally at 4am I went and took over. My husband was grumpy and tried and ready to give up. He went to his bed, and I lay down with E and helped him fall asleep. The crying has been so severe that the next day, the neighbors expressed concern about the 5 hours of crying. Result: My husband gave up with the nightime need for my son to fall asleep with me in bed with him, so I just had to lay down and help E go to sleep, off and on, for the following many years (until E was 9 or so). There is much more to this story, including, dated from that head-lock incident, E avoidant with my husband, disliking his father, and missing out on a father-son relationship.
I was so fortunate to have an angel of a lactation consultant who gave me so much practical advice that saved my sanity.
She taught me how to breastfeed laying on my side, she taught me how to wash a baby's bottom under a tap, she told me that she regretted sleep training her first child and that of all her three children her first was far more anxious and had MORE separation anxiety when they were older.
Her practical and sane advice really set me up and guided me. Everyone deserves an angel like her.
Wonderful article. I was somehow lucky enough to grow up in a family in America where cosleeping & breastfeeding at night was modeled to me. Once baby & I figured out the side-lying breastfeeding, which took a couple weeks to master with the first one, sleep deprivation wasn’t an issue. I raised 5 babies that way (which seemed totally doable because the newborn stage was not stressful!) All went on to become independent sleepers when they were ready. I truly can’t imagine doing it another way.
Also, the immigrants I've worked with from MX and Central America were kinda similar to the Hadza when lectured about not co-sleeping. They're kind of like "you want me to put my baby WHERE at night??"
Well, that seems a little strong. RCTs are a nearly miraculous tool for figuring out facts for which you actually have the statistical power to possibly figure them out. The problem comes when people then figure that, since a good RCT (really a meta-analysis) is better than anything else, *any* RCT must be the best thing going in its field. But you just obviously don’t have the statistical power to measure something like long-term social benefits of cosleeping, nowhere close. So here the RCT is irrelevant.
I think RCTs aren't great for some questions and not others, like when the conditions of the study aren't easily recreated or naturally occurring in real life. Minute 18 of that podcast is where I talked about it.
Here's a different perspective on the review of the literature on sleep training, which I found convincing when deciding for myself and my baby: https://pudding.cool/2024/07/sleep-training/
I'll also note that it seems like sleep training, when discussed in these contexts, often seems to be presented in a very extreme way, as in the introductory anecdote (I wouldn't want to listen to my baby scream for two hours either!), but doesn't need to be approached that way.
We set a 15 minute limit, which seemed pretty similar to the amount of time that he would scream in the car at that point, and I would go and soothe him until he fell asleep (sometimes nursing to sleep, sometimes rocking, whatever) if he was still crying at 15 minutes. Doing that took about a week before he would fuss for a couple minutes and then fall asleep. He now just rolls over and falls asleep when I put him down. He also continues to wake up once or twice a night for a snack, and I continue to respond to that. But what he no longer did was go down in his crib, then wake up 45 minutes later, then cosleep with me and wake up constantly throughout the night to snack/cry/roll around in the bed while I stayed awake and miserable. My sleep and quality of life improved massively as a result. I'm sure there are babies for whom that approach wouldn't work, but just wanted to share a different anecdote from more of a middle ground, which is where I think many people end up.
So nice to hear of another mom doing a middle ground approach! After co-sleeping for the first six months of my daughter's life, we recently did a middle ground approach where I sit in the rocking chair next to her crib while she figures out how to fall asleep. Sometimes she cries, but I'm there to reassure her she's not alone. The first few months of co-sleeping were so beneficial for both of us, but around six months she decided she'd had it and wanted her own space, I kid you not. Co-sleeping suddenly became torturous and she refused to go to sleep at the beginning of the night. She'd been napping in her crib since she was 2 months so I guess she liked it there enough to want to transfer completely!
I have the benefit ( I say this loosely lol) of being half zimbabwean and half american. I was raised born and raised in southern Africa and moved to the US for college and subsequently had babies. It AMAZES me at the lack of connection the west has to matrescence. My partner and I were told we were "ruining" our kids for holding them and wearing them as well as breastfeeding past 1. I remember after giving birth the nurse insisted they sleep ABC " Alone, on their back, in a crib" . After one night of poor sleep constantly waking up to nurse my baby I said to hell with that and did what I had seen all my aunt, cousins, and sisters doing as a kid. Co-sleeping, babywearing are the basis of how we protect and take care of our offspring.
It's because Americans (and any place where the mother needs to work relatively quickly after birth) need to be able to sleep through the whole night (ish) and the baby crying wakes you up.
There's no medical reason to do sleep training.
I went back to work within a month of giving birth, and I did not sleep train. I think also being exposed to bedsharing helps normalize it as well.
Oh, for sure not everybody needs to sleep train, but it IS effective for getting a kid to sleep through the night if needed!
It’s cruel
Yeah, well it's effective at making sure the parents sleep through the night and can perform effectively at work so they don't get fired and be unable to feed their kid
In the article above is says that the mothers in the trial don't actually sleep much better, even if the infants are sleeping longer 🤷♀️
Did you read it?
The baby learns nobody cares that he’s sad, lonely, hungry.
Nope Peter. Breastmilk is free....
I developed chronic insomnia post partum. I would sleep less than 4 hours a night and was slowly losing my mind, health and happiness. I tried medication, supplements, sleep hygiene - everything. My daughter was getting up 3-5 times a night and would want to play for hours. Eventually my husband ended up handling almost all wake ups in an attempt to help me get out of the insomnia cycle. We were all exhausted. We ended up doing Taking Cara Babies - the gentle approach to sleep training when she was a year old. Within 2 nights she was trained. My heart hurt for her little cries those 2 nights, but my entire family’s health improved. She was and continues to be a very happy and congenial toddler and feel we are very close. For me, I wish I had done it sooner. I agree we need more research, but my biggest takeaway is that we should listen to our mother instincts! My opinion is some babies and moms may benefit from it - others may not.
I also developed insomnia postpartum. It was absolute hell. I did the newborn Taking Cara Babies program and never needed any sleep training beyond that (baby still woke through the night until 7 months, but it was typically once by then, maybe twice). And thank god I did because I absolutely could not have handled multiple long term night wakes in addition to the fact that my body just refused to shut down and sleep. So sorry you had to deal with that - it was one worst, most lonely times in my life.
I'm almost of the mind we don't really need research on this. We need support for parents and longer parental leaves so this issue doesn't become such a tortuous pressure-cooker. With how much kids grow and change in the early years, I really can't see how sleep training or not would be such a major factor versus the literally thousands of moments we spend nurturing, cuddling, assuring, holding boundaries and teaching skills. It just feels like another way to shame moms for choosing "wrong" or not.
Insomnia is awful, and I've struggled with it both in pregnancy and postpartum. I have found different methods to deal with it as I personally cannot cope with listening to a baby cry for extended periods. Also I don't really blame my babies for my insomnia, their wake ups certainly don't help but there are many nights when they're lying next to me sleeping peacefully while I stare at the ceiling.
Everything about childrearing is so emotive and it's hard not to feel defensive about choices made. There are many things I wish I had done differently with my firstborn based on what I know now. Our culture and society can make it really hard to follow what our babies expect from an evolutionary perspective, but that means we should be trying to change culture and society, not trying to change the babies.
YES, and how even would you account for all of the many moments of connection/disconnection that happen apart from sleep in a parent and child's day?
I’m a SAHM to twins and I wish I had done sleep training even earlier. Sleep deprivation is torture and one bad night of crying is worth the peace that we have now. If moms want to co sleep and get up 6 times a night with their baby, that’s awesome! But I don’t
Technically I didn't have to "get up" 6 times a night as my baby was right next to me. Most of the time he would stir slightly and while laying down half asleep I'd nurse him and then continue sleeping. When we cosleep our sleep cycles (amongst other things) sync up which helps moms feel more rested. I think sleep deprivation sounds awful but I don't think training our babies not to cry for us is the only solution to the situation.
My experience currently! It was really hard when the 4 month regression hit, but then we started cosleeping (we are at 7 months now with every 90 min wake ups still) and maybe a few weeks in something clicked and the sleep cycles aligned and I’m rested and thriving. If someone would’ve told me I’d “wake up” every 90 minutes for 3+ months straight and still feel great I would’ve been SHOCKED. But it somehow works 🤷 happy I didn’t give up on it.
What I did give up on was trying to control his sleep and not being stressed about it takes a weight off.
I wish that had been my experience! After trying cosleeping (which did not help and increased wakeups for us) and 10 months of going back to working full time on no sleep, I couldn’t continue once she hit a year old. I really appreciated the Taking Cara Babies approach.
yeah I think across the board co sleeping increases wake ups -- had that too but again just the half asleep thing. apparently there's some evolutionary biological reason why the waking up more is beneficial. easier to say when you're not trying to balance that with modern life.
it's all very difficult!
I was severely sleep deprived with my third who didn't sleep, on top of insomnia. The Taking Cara Babies program did nothing, I even hired a sleep consultant. He just didn't sleep until he got older. Co-sleeping was the only way to survive, and the nights of CIO were just torture on top of everything. Just adding this in for the moms reading here who want to just cry when they hear "I did such-and-such sleeping program" because it's not working. I had to delete some acquaintances who only had one baby and were claiming success with Cara lol, my mental health was so bad. He's 5 now, I eventually slept again.
I hear you - it is hard to describe how you feel after 10+ months of totally inadequate sleep, but it is definitely a form of torture. Each morning I commuted to work I would repeatedly slap myself in the face to stay awake - it felt ridiculous (because it was). It just wasn't workable for my situation.
I appreciate your writing - I found you through your pieces critiquing Erika Kosimar - but I think you are committing a few mistakes here.
First is your suspicion that if evolution and science don't match, the problem must be in the science. Evolution can provide a hypothesis - for example, that sleep training may cause developmental mental health issues - but science isn't obligated to confirm this hypothesis. It's possible that we evolved to cosleep AND that not cosleeping doesn't cause long-term harm. So to me, your claim sounds like a form of the appeal to nature fallacy - that only what we evolved to do is good and right, and the science is sus if it doesn't match it.
Second, I think the sentence "We have no idea if what I did to my son is okay, and I will forever be asking questions" is open ended and can make parents more anxious than they already are. Part of why I appreciate the work Emily Oster is that she helps lower concerns that lead anxious parents into thinking each and every one of our actions may cause long-term damage. IMO, kids are flexible, and being anxious about our every misstep may affect their mental health in other unintended ways.
All this said, I really do appreciate you critiquing the research in this piece. I just think it could benefit from tightening some of the claims around evolution, and steering clear of the fear-based claims that play into the culture war around sleep training. I hope this is helpful!
I really appreciated "Sweet Sleep" by La Leche League, that reviewed research on sleep training and co-sleeping. They mentioned in the book that research showed that sleep trained infants did not get better sleep, they were just quiet, but that they had as many wake ups as prior to "sleep training", and that their salivary cortisol was elevated at night even though they didn't cry out. I never went to the primary sources, because who has time for that, but I found that book useful for the other side of the research.
Came here to say this too - the data on infant wake-ups is very limited as it only takes into account any wake-ups that the parents report. Considering sleep training essentially teaches the infant not to signal to the parents during sleeping hours it’s pretty easy to see the limitations there!
It’s amazing that 100% of mothers don’t have depression in the US with the whole breastfeed but no cosleeping message! I’d also like to see exploration of the role of Back to Sleep on rates of maternal depression. Babies don’t sleep well on their backs in many cases.
My son always rolls onto his side which works out great for the side-lying nursing he does all night
I don't think this essay handles the "evolutionary evidence" around co-sleeping appropriately.
Our Hunter-gatherer ancestors also didn't use vaccines, and the clear pain-avoidance response shown by children and their parents could be taken as a clear "evolutionary evidence" that vaccines cause harm. As a science writer, I hope you can spot the fallacy here. Evolutionary impulse knows nothing about vaccines, and therefore should make zero contribution to our priors.
Nikhil Chaudhary handles the evolutionary role of co-sleeping appropriately - it indicates that in a hunter-gather environment, co-sleep is an effective way to shelter infants from the elements and predation. Given that we already know that infants in temperature controls homes away from predators are not in physical danger, we know the evolutionarily ingrained behaviors simply do not apply here. And since there is no evolutionary selection on the quality of infant or maternal sleep, we also know that evolution has nothing to say about this.
The danger of co-sleeping on the other hand, in terms of possibly suffocating infants, is real and documented in the modern environment. Since you read Oster, you know that this risk while real is somewhat overstated and may be driven primarily by parents sleeping on couches and/or in a state of intoxication. Of course those things also don't exist in a state of nature either.
If you want to co-sleep despite an absence of specific scientific support you are certainly welcome to do so. Oster frequently makes this point, that nothing in the consideration of science takes away the importance of individual agency in parenting.
But please don't mistake "your idea of what is natural" for "scientific evidence".
Ah yes, Jeff, thank you for bravely stepping in to compare co-sleeping with vaccines, the rhetorical equivalent of comparing a campfire to a centrifuge.
The idea that evolution “has nothing to say” about infant-maternal sleep because there wasn’t a randomized control trial conducted in the Pleistocene is, let’s just say, adorably reductive. Of course, evolution didn’t engineer for blackout curtains and memory foam mattresses; it engineered for survival, which just so happened to favor the babies who stayed close to their parents and didn’t freeze to death or get eaten by leopards. To suggest that those survival strategies are now entirely obsolete because we invented thermostats is like saying hunger cues no longer matter because we have Uber Eats.
You cite Nikhil Chaudhary approvingly, but then you declare that since evolution didn’t select for maternal sleep quality, it must be irrelevant, as if sleep deprivation hasn’t been shown to degrade maternal responsiveness, lactation, and mental health, all of which very much do affect infant survival and maternal fitness. Evolution, it turns out, isn’t as narrowly blinkered as your argument.
This whole “your idea of what is natural isn’t scientific evidence” line is a straw man. Nobody is saying natural equals good, full stop. The point is that an evolutionary lens informs scientific hypotheses; it doesn’t replace evidence, it helps frame it.
So yes, Jeff, we agree: don’t mistake instinct for proof. But also don’t mistake pedantic contrarianism for clarity. The science here is evolving. kind of like our species. Try to keep up.
OP says "I believe the evolutionary science behind co-sleeping (and maternal responsiveness to crying) is so compelling that we would need many, replicated, high-quality studies in order for me to be convinced that it’s totally safe and has no negative effects on children or mothers." This is not framing evidence, this is replacing evidence.
I think the unintuitive safety of vaccines is a compelling example, but there are a lot "evolutionary instincts" which are maladaptive today. Eating sweets is a evolutionary impulse - It's clearly telling us "something" that the body wants to eat sweets, but it's not a good prior for optimal nutrition.
I don't know anyone making an evolutionary argument in favor of sweets, but in fact you will find a lot of bad takes on the Internet that come from the supposed wisdom of our evolutionary instincts. I don't wish to take those on as priors, actually.
We're supposed to be taking parenting tips from the ancestral past, but we're talking about a time and place with an infant mortality rate was x10 higher than what we have today. Its no leap to say the driving considerations behind infant health in that environment are just vastly different - as different as eating sweets in a cafeteria is from scarfing wild fruit before a long winter.
If you are saying we should follow available scientific evidence from modern environment, and disregard the biases going into that, I can agree with you there.
I don’t think the evidence in favor of sleep training is at all comparable to the evidence for the efficacy and safety of vaccines. We have a strong drive to avoid puncture wounds and introduction of foreign substances to the body. An organism lacking this drive cannot survive long.
However, we also have plenty of evidence to update on this prior: in the specific case of properly developed vaccines, injection is not dangerous and in fact salutary. And the downside risk of being unvaccinated can be serious. This does not mean the drive to avoid wounds and foreign substances is completely upended!
Likewise, we have a strong drive, shared with all primates, to maintain close physical content throughout infancy. Is this drive causing some harm? Does the intervention of sleep training have some benefit comparable to vaccines? It seems to me that we have 1/100,000th of the evidence compared to vaccination, for a much less well defined problem and benefit. There’s also a good amount of evidence that withholding physical touch and reassurance can have catastrophic effects at high “doses” (Romanian orphanages, Harlow’s “wire mother” experiments, still face experiment, etc)
It could well be that these effects are non linear, and don’t appear until you reach a certain threshold of withholding. But letting a baby cry it out night after night seems like a significant dose.
The point is that there *is* no scientific evidence, in essence, on this question. The RCT discussed is self evidently almost entirely worthless, except to rule out that either sleep training or not sleep training will cause overwhelmingly massive long term harm. The evolutionary evidence is that some 99.99% of all human babies that have ever been born have co-slept with their mothers, and there is literally no evidence that this is actually harmful outside of other kinds of pathological modern situations. If you can’t see this is an obvious slam dunk for trusting the prior over the one mediocre piece of science, well…I’m praying for you.
There actually is scientific evidence that it co-sleeping poses a rare risk of accidental suffocation of infants. This is why the AAP and NHS advice against it.
OP doesn't address this. Instead she analyzes the studies saying there are no downsides of sleep training, and concludes those studies aren't good enough. And on that basis, that is without any supporting experimental evidence, decides sleep training must be harmful or risky for the well-being of children in a way not detected by studies.
Would be better for OP to just say she's chancing the (rare) risk of suffocation because co-sleeping brings the family comfort and joy, which is an entirely legitimate choice for a parent to make.
There's not, though; that's what all the discussion of scientists failing to distinguish between different details of the context of co-sleeping is about. There's no study suggestion that co-sleeping supine with a breast-feeding mother, without a pillow or excess linens, etc, is any suffocation risk whatsoever.
Don't worry, Jeff, you're fighting chatGPT on this one
Breastsleeping does more than protect infants from the elements and predation. It confers protection from SIDS, facilitates extended breastfeeding, and improves sleep quality for mothers.
How I wish this was true for me! I have tried to tried to breastsleep but found out that my baby woke even *more* often and I got zero sleep.
I know right! my first woke up crying evert 15 min even when I was next to him and boob was available. It wasn't until I sleep trained him at 6 months that we all got some sleep and he started waking up only at 6am, which was clearly hunger after 10h of sleep and so I breastfed him.
Thank you, Jeff. Well articulated. I agree wholeheartedly.
Huh? *no* selection for quality of sleep? That’s a rather absurd overstatement.
Thank you for this extremely nuanced article! As a FTM, I was terrified of SIDS and so I got TCB's newborn course and followed everything she said to a T, minus the whole drowsy but awake, don't nurse to sleep BS (does that work for anyone??). My daughter was sleeping 12 hours by 12 weeks alone in her crib. I congratulated myself for following the rules and having a wonderful sleeper. And then around 8 months, she started teething, she got a couple ear infections, and her separation anxiety kicked into high gear. I tried letting her cry but caved after five minutes when I could tell she was truly panicking. And then I read Sweet Sleep (LLL) and Dr. James McKenna's book, memorized the Safe Sleep Seven, and taught us both how to safely breastsleep and bedshare. Total gamechanger. I was sleeping better than I had since before I got pregnant - having her next to me, once I got used to it and stopped holding myself rigidly in place out of fear of crushing her to death, was SO much more restful than waking up 20 times a night to stare at the monitor glaring in my face to make sure she was breathing. We always started her out in her own bed and brought her to our bed after her first wake, but I continued bedsharing with her through weaning at 22 months old, up until she randomly started sleeping through the night in her own bed of her own accord at 2.5 years old. Which was great timing because I was newly pregnant with my son, whom I have bedshared with since birth (he is almost 8 months old). This time around it was a total no-brainer. He can sleep with me as long as he needs to. I feel like I get really good sleep even though he nurses about every two hours around the clock, and I love having him right there with me. Trying to do it any other way feels like such a waste of energy and precious time with my baby. I work outside the home full-time, so maybe I'd feel differently if I didn't, but for us, for now, it's the perfect fit.
I think the most fascinating thing for me was before when i worried about putting my newborn in the crib i would wake and panic searching for her in the sheets.
As soon as i said to hell with it and let her sleep next to me they vanished. Instantly vanished.
I’m not sure what that says about bedsharing but it sure is interesting.
Also, thank you for putting into words the way i felt reading that study, and most, sleep training studies. I just ended up feeling very…not reassured.
Every mother I've ever spoken to reports the same--waking up in deep confusion trying to find where the baby is in the bed. Every bedsharing mother I've spoken to reports it went away when they started bedsharing.
I wonder if it’s because we are subconsciously aware of where they are at all times
Before I started bedsharing with my first, I would wake in a panic saying, “Baby, baby” and looking for her frantically. My subconscious could not reconcile her being any distance from me during sleep. So fascinating!
Yes this exactly
My parent and their ancestors are from a “family bed” culture (there’s a special word for the bed that everyone in the entire household sleeps on together, for them it was 7 people) and they disliked their experience so much they were determined to rise above poverty and eventually buy a house where every kid had their own room with a door that closed. So I have observed the maternal instinct can go either direction. I feel like the family bed concept is romanticised by affluent westerners, and also taken out of context with other cultural practices. I don’t think the benefits translate directly to us in the west, as in my heritage culture, the bed sharing pairs with other aspects such as waking with the sun/going to sleep at sunset (much harder to go to sleep with your baby when the sun sets at 4:30pm in the winter in the US when your job ends at 5pm), postpartum rest (where the mother recovers at home for 1 month while female relatives come over and take care of the house and chores AND baby), infant pottying (it’s useful to sleep with baby when you don’t have a laundry machine or diapers, so you can potty them when they wake in the middle of the night. turns out a lot of babies wake and cry because they need to pee!), and filial piety + anti-individualism + corporal discipline (I have observed the kids in the US to overall have a way different relationship with their parents). My parents worshiped their ancestors and had the winter months as holiday, we americans worship work productivity and never rest. The benefits of sleep practices from one doesn’t feel like a useful point of comparison to the other.
Very interesting analysis! I am very swayed by your argument that everyone used to
Co sleep. Here in Austria, das familienbett “family bed” is very common. Several friends removed all wardrobes and furniture to create a 3 meter wide bed to accommodate all family members. At the hospital where I gave birth, midwives encouraged me to sleep with my newborn in the hospital bed. On the other side , it’s weird because I haven’t seen a single doctor promoting co sleeping on social media. For example, I follow @thatsleepdoc on instagram and he’s very adamant that sleep Training is better for parents- helps them be more responsive, get better sleep, and feel less frustration and there are no long term consequences for kids. Granted, he’s in the USA, speaking to an American audience who needs to go back to work and truly cannot cope with months of poor sleep.
American infant advice is so faulty that when my husband and I brought our newborn first baby home, we were absolutely shocked that she didn't want to sleep alone in the flat, hard, cold bassinet we'd procured for her. We did do minimal sleep training with her, but it was hell. I still sleep with our second who is nearly two and breastfeed her 2-3 times a night and I still get so much more sleep than I did with my first!
One of my twins (fraternal) stopped waking up after 3 nights, and the other NEVER stopped crying and never stopped needing to be near me at night for years until he was 6 or 7. Individual differences might be key here. Sleep training can work for some kids but not all.
The son, E., who needed to be near me at night, at age 3 or 4, would every night come into my room (very close by, where I slept in a double bed with my husband). I eventually put down a mat right by my side of the bed, and E would just lie down on the mat and sleep. My husband was fine with that and E didn't try to get up in bed with me. But E also required that I lay down with him to fall asleep each night, which I did. But this was difficult since I would sometimes fall asleep there, it would take a long time, and so that would occupy my evening. My husband got mad and decided we just needed to try 'cry it out' one more time,no more coddling. So my husband commandeered the situation and basically was there with E in a hammer lock head hold while E cried and flailed and protested and I kept away in a separate room. E cried for hours, and my husband was determined to keep E from running to Mommy. E did not stop crying. Finally at 4am I went and took over. My husband was grumpy and tried and ready to give up. He went to his bed, and I lay down with E and helped him fall asleep. The crying has been so severe that the next day, the neighbors expressed concern about the 5 hours of crying. Result: My husband gave up with the nightime need for my son to fall asleep with me in bed with him, so I just had to lay down and help E go to sleep, off and on, for the following many years (until E was 9 or so). There is much more to this story, including, dated from that head-lock incident, E avoidant with my husband, disliking his father, and missing out on a father-son relationship.
I was so fortunate to have an angel of a lactation consultant who gave me so much practical advice that saved my sanity.
She taught me how to breastfeed laying on my side, she taught me how to wash a baby's bottom under a tap, she told me that she regretted sleep training her first child and that of all her three children her first was far more anxious and had MORE separation anxiety when they were older.
Her practical and sane advice really set me up and guided me. Everyone deserves an angel like her.
Wonderful article. I was somehow lucky enough to grow up in a family in America where cosleeping & breastfeeding at night was modeled to me. Once baby & I figured out the side-lying breastfeeding, which took a couple weeks to master with the first one, sleep deprivation wasn’t an issue. I raised 5 babies that way (which seemed totally doable because the newborn stage was not stressful!) All went on to become independent sleepers when they were ready. I truly can’t imagine doing it another way.
Great take! I have the same frustrations/disagreements around the obsession with RCTs as the holy grail of science as if they represented real life when they do not. Discussed this with Emily Oster on her podcast when I went on to discuss midwifery!: https://podcasts.apple.com/us/podcast/parentdata-with-emily-oster/id1633515294?i=1000672478249
Also, the immigrants I've worked with from MX and Central America were kinda similar to the Hadza when lectured about not co-sleeping. They're kind of like "you want me to put my baby WHERE at night??"
Well, that seems a little strong. RCTs are a nearly miraculous tool for figuring out facts for which you actually have the statistical power to possibly figure them out. The problem comes when people then figure that, since a good RCT (really a meta-analysis) is better than anything else, *any* RCT must be the best thing going in its field. But you just obviously don’t have the statistical power to measure something like long-term social benefits of cosleeping, nowhere close. So here the RCT is irrelevant.
I think RCTs aren't great for some questions and not others, like when the conditions of the study aren't easily recreated or naturally occurring in real life. Minute 18 of that podcast is where I talked about it.
Here's a different perspective on the review of the literature on sleep training, which I found convincing when deciding for myself and my baby: https://pudding.cool/2024/07/sleep-training/
I'll also note that it seems like sleep training, when discussed in these contexts, often seems to be presented in a very extreme way, as in the introductory anecdote (I wouldn't want to listen to my baby scream for two hours either!), but doesn't need to be approached that way.
We set a 15 minute limit, which seemed pretty similar to the amount of time that he would scream in the car at that point, and I would go and soothe him until he fell asleep (sometimes nursing to sleep, sometimes rocking, whatever) if he was still crying at 15 minutes. Doing that took about a week before he would fuss for a couple minutes and then fall asleep. He now just rolls over and falls asleep when I put him down. He also continues to wake up once or twice a night for a snack, and I continue to respond to that. But what he no longer did was go down in his crib, then wake up 45 minutes later, then cosleep with me and wake up constantly throughout the night to snack/cry/roll around in the bed while I stayed awake and miserable. My sleep and quality of life improved massively as a result. I'm sure there are babies for whom that approach wouldn't work, but just wanted to share a different anecdote from more of a middle ground, which is where I think many people end up.
So nice to hear of another mom doing a middle ground approach! After co-sleeping for the first six months of my daughter's life, we recently did a middle ground approach where I sit in the rocking chair next to her crib while she figures out how to fall asleep. Sometimes she cries, but I'm there to reassure her she's not alone. The first few months of co-sleeping were so beneficial for both of us, but around six months she decided she'd had it and wanted her own space, I kid you not. Co-sleeping suddenly became torturous and she refused to go to sleep at the beginning of the night. She'd been napping in her crib since she was 2 months so I guess she liked it there enough to want to transfer completely!