Crying-It-Out: An Addendum

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I recently posted information on crying-it-out and received some interesting comments, but one was a particularly interesting question that I felt warranted a fuller explanation for everyone.  You see, the person questioned the conclusions from the Middlemiss study which found high cortisol activity in children undergoing a sleep training program in New Zealand.  The commenter rightly points out that the research itself does not show a cortisol spike pre- to post-bedtime and so instead believes the high cortisol found in the infants on both days one and three is due to general all-around stress and that it might be very different for a child in his or her own home undergoing CIO.

This is where I need to explain.  We all know the limitations of science – the best study is still hardly conclusive.  After all, there hasn’t been (and never will be) a study that actually shows that smoking causes cancer, despite the general knowledge that it, in fact, does.  That’s not to say this one study provides anything near the level of evidence built up in the smoking case, but it does highlight that when examining research, we make logical deductions in order to analyze the results we’re presented with.  I do this each time I write about a study, though I don’t usually include this thought process because a) it’s long, and b) I imagine it’s generally boring.  However, for the sake of clarity, honesty, and an example, I have decided to share this process for anyone interested.  As with anything I write, you are free to disagree with the conclusions I’ve reached, but you will at least realize the process I go through as I read and review the literature cited in my posts.

The study:  The cortisol levels reported in the Middlemiss study were obtained at the beginning of the bedtime routine and 20 minutes after the child has fallen asleep.  On both days 1 and 3, the levels were elevated, but did not significantly increase pre- to post-sleep time.  As the commentator pointed out, someone could say that this is evidence that CIO does not cause an increase in cortisol.

Facts agreed upon:  Both the commentator and I agree that the levels of cortisol displayed by the infants is high.  There is no debate there.  As a reference point, the levels obtained in this study are higher than those obtained in other studies examining infant’s cortisol reactions to a known high-stressor[1][2].  This is echoed by the conclusions I cited from the researchers themselves that the cortisol levels displayed were indicative of “high levels of physiological distress”[3].

The problem:  There are two possibilities accounting for the cortisol data obtained:

(A) That the high-cortisol levels are associated with the sleep routine and the CIO methodology.

(B) That the infants are generally stressed and this high level of cortisol is indicative of all around stress, presumably due to being in a different environment from home (i.e., the sleep training centre).

I landed on the side of (A) which I will explain, but I will first explain why I did not land on (B).

The logical problem of (B):  First, we have the problem of the actual cortisol levels being as high as they are at the end of the day.  The natural circadian rhythm has individuals (children too) showing their highest levels earlier in the day with levels naturally declining over time (the rhythm is diurnal).  While this has been occasionally found to not be the case in certain individuals or infants, for it to be the case for all infants in the program is highly unlikely (for example, in one study using 11 infants, only 2 were found to have higher cortisol levels at night than morning[4]).  And if these results were being driven by four or five extremely high cases with the rest showing low cortisol activation, the researchers would be remiss and unethical not to mention that.  I don’t believe that to be the case.

The other reason to see consistently high cortisol levels is when there is chronic stress.  Day one of a program would not be enough to elicit this consistent level of stress suggested, particularly as the daytime portion of the program solely involves activities with mom.  As stated in the paper, “During infants’ awake times, mothers and infants could spend time in the shared lounge with other program participants, in the mothers’ room, or could run errands or take walks with their infants.”  Therefore, despite the new surroundings, the infants were with their mothers, and as Megan Gunner’s research has shown, parents serve a very important role in attenuating the cortisol stress response[5].  And given that the environment was new, it should not elicit a chronic stress response, but rather an increase which slowly decreases with time, the typical stressor response.  A chronic stress response would suggest that there are parenting issues at hand causing all children to have insecure, neglectful, or abusive parents—the primary reasons to see chronic stress in an infant[6].  This would mean that the stress response was a continuation of chronic stress in the home environment, and while there were reported sleep problems in these families, there is no reason to believe that there was child maltreatment in the form of neglect or abuse strong enough to elicit this type of chronic stress response, particularly as the mothers were not referred for any psychiatric help in addition to sleep training (and in fact, one of the requirements of the study was that mothers were not taking medication for post-partum depression).  One last reason I discount the chronic stress hypothesis is that while chronic stress initially results in the higher cortisol output later in the day, as time passes, chronic stress seems to change its effect on cortisol and results in a lowering of baseline cortisol[7], something that was not demonstrated in the current study if the stress had been ongoing for a period of time at home.

Now, some might be thinking that the new environment should elicit some stress response on the first day, but that then ignores the same high levels found on day three, when the new environment is not so new (children do adapt quickly, especially with a parent present).  So the high levels on both days seem to work to counter the idea that it’s the environment per se that’s causing a stress reaction.  But are there stressors that cause increases in evening cortisol?  Greg Miller and colleagues examined the type of stress by cortisol response[7] and found that afternoon/evening samples with an increase were linked to the following types of consistent stressors: physical threat, social threat, traumatic stressor, uncontrollable stressor, loss, and shame.  I don’t believe that these infants were faced with any of these types of stress on an ongoing basis or even on a regular basis when starting in the program so on top of discounting chronic stress, even the types of stressors known to elicit evening peaks, none of them seem relevant to the entire group of infants on hand.  Daytimes of spending time with mom, going for walks, and running errands or playing with other moms and kids is hardly under the category of these forms of stress, even if it does take place in a new environment.

Finally, there is research on the cortisol effects of beginning a new school year on school-aged children[8] and on starting daycare for infants and toddlers[9][10].  The school year research shows that the stress of the new school year leads to a greater decrease by the end of the day.  That is, the slope from morning until evening is steeper than when the child has adapted to the new school year.  Of course, this is research with older children so it’s questionable as to how pertinent it is, but it is there and to me, serves as just that added extra, not as a study that helped shape the view against (B).  The daycare research on infants and toddlers does find an increase in cortisol across the day in daycare (though in less than half of infants[10]), but – and this is a big ‘but’ – being in the new environment of daycare during an adaptation period with mom did not result in an increase in cortisol for the infants who were securely attached[9] (and remember that synchrony is a sign of secure attachment so it’s fair to assume these infants were at least relatively securely attached).  Mom’s presence in the new environment worked to eliminate the expected rise in cortisol from an infant being placed in a new environment.

Why I sided with (A):  It wasn’t just the lack of logical reasoning with (B) as to why I chose (A), there is the additional fact of mom’s cortisol levels.  Pre-sleep routine mom also showed signs of stress, as demonstrated by heightened cortisol levels.  Why would this be the case?  I do not believe it is because of the daytime environment, and because of the drop in cortisol for moms on day three (post-bedtime), it is clear mom’s cortisol can be reduced.  I believe it’s because she knew the routine was coming.  Now, does this mean baby knew the routine was coming?  No.  But it means there were cues to the nighttime routine beginning which the infant may have picked up on (they’ve been known to pick up on a lot), but it also means that mom was giving off cues signaling distress.  Remember that synchrony works both ways – mom picks up on infant emotions and vice versa.  A calm mom can elicit calmness in her infant.  A stressed mother can elicit stress and so a mother that is in sync with her child and starting to dread the CIO routine that is to come may very well elicit the high cortisol response in her infant.  The notion that because the saliva cortisol sample suggests a stress response 20 minutes prior to the initiation of the bedtime routine does not eliminate the notion that it was the impending bedtime routine that elicited the stress.  It simply requires that the infants either picked up on a cue to the impending bedtime routine (which is not unheard of) or that they picked up on mom’s stress about the impending bedtime routine.  Importantly though, the stress of CIO remained because if CIO did not cause stress, the levels of cortisol would have dropped during the bedtime routine and sleep period, which they did not.  By day 3, mom’s cortisol had dropped, but the infant would now be expecting the CIO routine – remember infants pick up on routines very easily and well – and thus the high cortisol pre- and post- on day 3 is, to me, indicative of the CIO routine.

Other conclusions:  I must add though that this debate has nothing to do with what I perceive to be the most important conclusion gleaned from this research—that infants who are not crying are still experiencing distress.  Parents typically speak of CIO as being a few days of hell but then everything is fine.  What the Middlemiss study showed us, though, is that that may not always be the case.  Opponents of CIO techniques typically state that CIO teaches infants that someone will not always be there to help them when they are distressed, and here is research supporting that.  There are infants who very clearly and quickly learned that their cries were not going to be responded to in any manner and so stopped crying after only two nights.  And yet their distress levels remained very high.  So they didn’t learn to “self-soothe”, they learned to keep quiet and preserve energy (as crying results in a large energy expenditure relative to other activities[11]).  If no one is coming to help you, you simply waste energy by calling out.  It doesn’t make you less scared, alone, or distressed.

There will always be the question of how long this distress continues on for.  No one expects this rise in cortisol to continue forever, but the fact that it happens at all tells me that we’re not doing our infants any service by utilizing CIO techniques.  Why?  Because it seems clear that the first lesson they learned is that they can’t trust that mom will be there to help.  Whatever else comes next, that’s a pretty shitty lesson to learn so early in life.  The fact that one of the “positive” side effects of CIO, as reported by the Sleep review[12] is fewer bouts of crying at all times suggests that these infants are internalizing and extending this message.  Further support for this comes from the same daycare research[10] as infants who were insecurely attached demonstrated consistently high cortisol levels during both the time when mom was there and after she left, despite showing low levels of crying and fussing behaviour.  As to the question of how long the distress continues for, again the daycare research may provide some hint.  Securely attached infants, when separated from their mothers, demonstrated the rise in cortisol that the insecurely attached infants showed during the adaptation period.  These levels did not drop for nine days (the longest they measured cortisol before a 5-month follow up).  Fussing and crying behaviour decreased over the nine days (though for securely attached infants, it was still higher than when mom was there), but cortisol levels remained equally high from day one through day nine.  It’s also worth noting that these infants did have someone to respond to their distress at daycare – they were not left alone – and yet they continued to show physiological distress at the separation from their mother.

I know some people will make different conclusions based on the studies I’ve discussed above and the possibilities surrounding them.  That’s fine.  But I was asked why I stated this (with a hint that I was being dishonest in my reporting) and I have always strived to be transparent so this is a long-winded way of being transparent.  Hopefully this helps provide information for those who want more and further explains why I feel that CIO is not the way to go.


[1] White BP, Gunnar MR, Larson MC, Donzella B, Barr RG.  Behavioral and physiological responsivity, sleep, and patterns of daily cortisol production in infants with and without colic.  Child Development 2000; 71: 862-877.

[2] Goldberg S, Levitan R, Leung E, Masellis M, Basile VS, Nemeroff CB, Atkinson L.  Cortison concentrations in 12- to 18-month-old infants: stability over time, location, and stressor.  Biological Psychiatry 2003; 54: 719-726.

[3] Middlemiss W, Granger DA, Goldberg WA, Nathans L.  Asynchrony of mother-infant hypothalamic-pituitary-adrenal axis activity following extinction of infant crying responses induced during the transition to sleep.  Early Human Development in press.

[4] Kiess W, Meidert A, Dressendorfer RA, Schriever K, Kessler U, Konig A, Schwarz HP, Strasburger CJ.  Salivary cortisol levels throughout childhood and adolescence: relation with age, pubertal stage, and weight.  Pediatric Research 1995; 37: 502-506.

[5] Gunnar, M. R. (2006). Social regulation of stress in early childhood. In K. McCartney & D. Phillips (Eds.), Blackwell Handbook of Early Childhood Development (pp. 106-125). Malden: Blackwell Publishing.

[6] Cichetti D, Rogosh FA, Gunnar MR, Toth SL.  The differential impacts of early physical and sexual abuse and internalizing problems on daytime cortisol rhythm in school-aged children.  Child Development 2010; 81: 252-269.

[7] Miller GE, Chen E, Zhou ES.  If it goes up, must it come down?  Chronic stress and the hypothalamic-pituitary-adrenocortical axis in humans.  Psychological Bulletin 2007; 133: 25-45.

[8] Bruce J, Davis EP, Gunnar MR.  Individual differences in children’s cortisol response to the beginning of a new school year.  Psychoeuroendocrinology 2002; 27: 635-650.

[9] Ahnert L, Gunnar MR, Lamb ME, Barthel M.  Transition to child care: associations with infant-mother attachment, infant negative emotion, and cortisol elevations.  Child Development 2004; 75: 639-650.

[10] Watamura SE, Donzella B, Alwin J, Gunnar MR.  Morning-to-afternoon increases in cortisol concentrations for infants and toddlers at child care: age differences and behavioral correlates.  Child Development 2003; 74: 1006-1020.

[11] Thureen PJ, Phillips RE, Baron KA, DeMarie MP, Hay Jr WW.  Direct measurement of the energy expenditure of physical activity in preterm infants.  Journal of Applied Physiology 1998; 85: 223-230.

[12] Mindell JA, Kuhn B, Lewin DS, Meltzer LJ, Sadeh A.  Behavioral treatment of bedtime problems and night wakings in infants and young children.  Sleep 2006; 29: 1263-1276.

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  1. says

    I really appreciate this post. I have seen plenty of bloggers write about why we shouldn’t use CIO, and many of them cite science, but your writing on this topic is by FAR the most thoughtful and most honest representation of the science I’ve seen. Your point about how much we delve into the limitations of any study is interesting. I struggle with the same thing. I often find myself starting to write a post on a new study that I think is interesting, and then I find that I have to spend more time and words on trying to describe the limitations of the study than I do on the actual data and the coolness of it. This is a reality of science, and it is why we generally require a few studies before we start to accept that a hypothesis has some real weight to it. However, it is not always the best fodder for blog posts! All of this being said, I do think it is really important to describe the limitations of a study. The Middlemiss study, to my mind, has many limitations. The standard deviations for the data are enormous, there are no cortisol measurements from other timepoints (plus some samples from the home environment would be useful), and there is no control group. I don’t know why the authors didn’t look at trends in individual babies instead of lumping them into one big group with huge variability. All this on top of the fact that it was in a strange environment makes it difficult to interpret. In my mind, the limitations of the study are so great that we can really only speculate about the meaning of the data, and I don’t think it adds much to our understanding of what happens during CIO. You clearly disagree, but with this post, your readers can at least have an appreciation that the science and its interpretation is not cut-and-dry. This is a real service to your readers – both in their understanding of the topic and in their appreciation for how science is done. I truly appreciate it.

    Meanwhile, I clearly have a lot of interest in this topic, and I need to write about it on my own blog instead of leaving ridiculous long comments on yours. Maybe then you’ll come over to comment on my blog, and we can continue the discussion.

    Best wishes,

    • says


      I would go ahead and write on it! The more there is out there, the better I think, especially balanced, well-researched points of view. We may disagree on findings, but when doesn’t that happen in science? Notably though, the authors did run their analyses with and without outliers to ensure the integrity of the results so I do believe that helps assuage any concerns over the high standard deviations. But I, like you, believe a within-subjects comparison would be highly helpful in better understanding the data. (And of course, different data collection like a control group, but that becomes much harder to ask for post-hoc.)


  2. Estherar says

    I don’t think we have enough information to conclude (a) or (b). And it’s highly unlikely that infants’ cortisol levels were high pre-sleep on day 1 because of CIO that hadn’t been initiated yet.

    What may be key to the high cortisol levels is a point I’m not clear upon – who is actually doing the saliva sampling and the pre-bedtime care in the infants? From the article:

    “At all transitions to sleep, nurses
    and mothers would attend to preparing infants for transition to
    sleep by changing, feeding, and other naptime or bedtime activities.”


    “At this time, mothers received instructions regarding how
    to complete their own salivary sampling. In addition, mothers were
    informed that nurses would collect infants’ salivary samples…”

    vs. “Infants’ saliva was collected by mothers using microsponges.” later on in the paragraph.

    So if an infant was being handled pre-bedtime by a strange nurse (very possibly a different nurse each day), the high cortisol levels might be attributed to that.

    Since cortisol levels were not measured later on in the night nor during the day when they spent time with their mothers, we really can’t assume that the children were chronically stressed due to the unfamiliar environment, just that they were stressed around bedtime. what we can say, though, is that CIO doesn’t, apparently, contribute to a further rise in stress hormones beyond the stress experienced pre-bedtime (which would mean, not very much). Controls where Mom does all the pre-bedtime care and sampling, sampling cortisol levels during intervention at the child’s home, and sampling children in hospital who didn’t require a sleep intervention might help clarify these issues.

    There is also no evidence that you need perfect endocrine synchrony for a secure attachment to form or be maintained. The authors themselves expected this asynchrony to happen, and expected it to be temporary – synchrony will be restored once baby picks up on Mom’s lack of distress and realizes that learning to self-soothe isn’t as terrible as it seems. It’s a pity they only sampled cortisol on days 1 and 3, because a longer observation period might help determine when this happens and also help plot the “area under the curve” of elevated cortisol exposure (which would help compare this type of stress to other stresses, e.g., vaccinations, daycare attendance etc.). The asynchrony would also be consistent with Winnicott’s concept of a good enough mother:

    “The good-enough mother…starts off with an almost complete adaptation to her infant’s needs, and as time proceeds she adapts less and less completely, gradually, according to the infant’s growing ability to deal with her failure”

    Namely, temporary periods of asynchrony initiated by either the mother or the infant, while the other adapts.

    Alll in all, an interesting pilot study, but not at all the “CIO kills babies’ brains just like child abuse!!!!” that you were no doubt hoping for.

    • says

      A couple small comments:
      1) Nighttime has presumably been a stressful time for these families, leading to their presence at a sleep training clinic. That fact may account for the rise in cortisol seen in pre-bedtime sleep. However, as you rightly point out, nurses handled naps and so if the infants became aware that they were going to be separated from mom yet again, that may also have led to the increase and would also be linked to CIO methods.
      2) I would honestly be happy to see no ill-effects of CIO because it’s used so commonly. However, as I mentioned, I don’t even see the neurological evidence for “killing brain cells” (which isn’t it at all) being the main point or even necessary to argue harm. To me, the biggest problem is the “message” being taught to the infants about how they will be responded to when in stress. Even using Winnicott’s view of the good-enough mother involves responsiveness and knowing when your infant is ready to adapt. Not forcing the adaptation onto the infant. There’s a crucial distinction there and it’s why there’s ample research onto the negative effects of not being responsive to distress. The question is whether CIO on its own is enough non-responsiveness to cause problems.

      • Estherar says

        I’m not talking about stress that results from anticipated separation from Mom, but rather the stress of being cared for by a stranger, or having a stranger in close proximity. The babies had no way of anticipating on day 1 pre-bedtime that the appearance of a stranger would herald separation from Mom or CIO, so any rise in cortisol levels would probably be due to the stranger’s presence, rather than what she may or may not have represented later on.

        The rest of your post makes some interesting assumptions about infants and parents who sleep-train:

        1) That CIO sends a “message” to the child that she can’t depend upon the parent to respond to her cries. However, it’s quite clear that they also quickly learn that parents *do* respond, just not when they need to sleep (or in the case of Ferber – not in the way the baby might prefer at the time), and that Mommy will appear again in the morning. Which is possibly why you often hear of babies’ improved daytime disposition following successful sleep training (besides the simple fact that a better-rested baby makes for a better-disposed one, of course). In fact, I’ve heard quite a few parents attest to the fact that they become more responsive to their infant’s cries after they learn to self-soothe, because it’s far more likely their cries mean physical distress and not just bedtime fussing.

        2) That parents are somehow forcing adaptation on their infants before they’re ready. In your, only the infant is allowed to initiate any and all changes and it’s the mother who has to adapt (in this case, sometimes maintaining insane levels of fatigue). Winnicott very much talks about adaptation being a two-way street. Besides, initiating sleep training can be also be seen as the response to a mother’s correct perception that her infant (and she herself) need better quality sleep. Responding to an infants *needs*, even if it looks “really really mean” to Doc Sears and causes the infant temporary distress.

        Sorry, if you want to argue harm, you need to demonstrate actual harm as a result of CIO. Even cortisol increases are meaningless without a negative clinical effect that can reliably be attributed to sleep training. Otherwise, all you can legitimately do is express your dislike of a practice of which you don’t approve.

        • says

          It all depends what the pattern of behaviour was like at home. Many families try forms of CIO on their own at home, or even have infants separated from them for bedtime. Thus many infants most likely *do* realize that a separation from mom is imminent. The presence of strangers is not known to result in cortisol increases for infants when in the presence of mom, so I struggle with that interpretation. Possible, but in my mind, based on previous research, not probable.

          As to the assumptions –
          1) Sleep is just as important a time for an infant as the rest of the day. So even if a child only learns that parents don’t respond certain times, it’s still a message. I’m not sure how you claim that children learn parents *do* respond based on sleep training. The idea of self-soothing is interesting because it’s one we’ve put on infants. I’ve written elsewhere that self-soothing in the form of emotion regulation in older children is associated with responsiveness to distress in infancy. Self-soothing doesn’t seem to happen from being left on one’s own.

          2) I don’t doubt that there is a change in disposition for some families. In some cases, there are legitimate sleep concerns for an infant, but that is hardly the norm for people employing sleep training (at least as far as I’ve heard). Infants are supposed to rouse at night – it’s part of how we’ve evolved in terms of feedings and size of belly and make-up of breastmilk and just the sheer need to make sure oneself is safe. Physical distress isn’t the only type of distress – psychological distress is equally important and is often ignored.

          3) Adaptation does go both ways. However, I do not believe that forcing an infant to undergo separation and distress is “adaptive”. Mom generally knows when her infant is able to handle certain transitions and if there’s massive fussing and high cortisol levels, her infant isn’t able to handle the transition at that point.

          Of course, all of this would be primarily moot if we still had set-ups that were safe for baby to sleep with mom, which is what they are biologically wired to expect.

          As I said, you’re free to disagree, but I stand by my statements and the research cited. Sometimes before we get research demonstrating the effects, we have to rely upon what research is done and how we apply it to the case in point. Trust me, if I get a chance in the future, I will study CIO and other forms of sleep to see if there are reliable deficits.

          • Estherar says

            The presence of a stranger is associated with cortisol elevations. See van Bakel et al., Stress reactivity in 15-month-old infants: links with infant temperament, cognitive competence, and attachment security. Dev Psychobiol. 2004 Apr;44(3):157-67. If a stranger were to handle the babies while present, this would probably induce even greater stress (perhaps akin to a physical examination, which is a known stressor).

            1) Sleep is, indeed, a very important time of the day for an infant, as it is for us all. If infants don’t get enough of it (or large enough stretches of uninterrupted sleep), their physical and mental health will suffer. Sleep training clearly does not send the message to infants that parents won’t respond at all when they cry – I have yet to hear of a baby who stopped crying for any other needs as a result of being sleep trained. What it does seem to teach is that there are times when an active parental response isn’t appropriate, and Mommy will be back in the morning regardless. Self-soothing (and behavioral and endocrine self-regulation) is probably the next adaptive step, though the Middlemiss study doesn’t, unfortunately, address this. But we can see a similar pattern in other situations, such as daycare attendance, or, in fact, the physiological downregulation of the HPA axis that happens in the first few months of life.

            2) Funny, because I’ve heard quite a few concerns regarding the baby’s lack of sleep (“How can that child get by on so little sleep?”) as well as parental fatigue as being a reason to CIO. Other parents learn this in retrospect when their cranky, high-needs baby suddenly turns, post CIO, into an even-tempered, smiley baby who’s a delight to be around. Either way, precious few otherwise loving parents initiate CIO out of utter disregard for the baby.

            Babies may rouse during the night to feed, but it’s the rare normally growing baby> 4-6 months old who needs to feed several times during the night. Certainly no infant needs to wake every 45 minutes to feed, as some parents report. This is one of the reasons why no medical authority recommends CIO before that age (other reasons being the development of sleep patterns in infants and the aforementioned adjustment of the HPA axis, all which happen in early infancy). What happens in practice in older infants is that they feed more during the day to make up for the lost feeds at night. I certainly don’t know of any child above 4-6 months who started losing weight as a result of CIO (in contrast to programs initiated much earlier, e.g., Ezzo).

            3) You don’t have any evidence of cortisol elevations right now, and babies’ (and toddlers’) lives are full of adaptations that they may not like and may fuss about. Unless you’re suggesting that if a 1 year old pitches a fit on his first day at daycare, Mom should just give up her job and stay home – and we know for sure, unlike CIO, that this is a stressor that raises cortisol. Transitions are hard on the human race in general; we’re “biologically wired” to like our routines. Doesn’t mean we never should change anything in a baby’s life for fear of “breaking” her.

            I’ve taken enough of your blog space, and I apologize for this; I can only wish that if you do decide to study CIO, you re-examine your biases on the subject and adjust accordingly (or perhaps work with another researcher coming from the “other side”).

          • says

            First off, the van Bekel et al study does not demonstrate that the presence of a stranger elicits a high cortisol reaction. It shows that a stranger who also makes a scary robot go off (which children show visible fear of) causes an increase in cortisol – and as they said, it was fear of the robot that was positively correlated with cortisol, not fear of the stranger (which most children did not show). In fact, the findings of the van Bekel et al. study suggest that damage to the attachment relationship would be more detrimental to later stress reactions given their cognitive competency x attachment status interaction findings – that infants who showed higher cognitive competency and insecure attachment had the largest cortisol gains in the stranger/robot situation. I take it to suggest that infants who understood the threat and knew they didn’t have a secure base showed the highest stress reaction.

            Even the physical examination stressors cease to show up in most children past four months so the idea that the presence of a nurse (who actually should not have been around 20 minutes prior to the onset of the bedtime routine) caused it still is not supported by evidence.

            Sleep is important, but the idea that infants require the type of sleep we expect of them isn’t supported in the literature or cross-culturally. I acknowledge there will be cases where infants show a severe sleep disorder and that will need to be dealt with, but the idea that night wakings or trouble falling asleep at a set bedtime is “bad” just doesn’t hold much water. Travel around the world and you’ll find infants doing just great going to bed at 11pm or waking every hour – these behaviours are expected in other cultures and thus not treated with fear and panic. Of course, in these cultures mothers tend to have lots of support and so don’t suffer from PPD which is, in my opinion, one of the biggest contributors to infants’ fussy behaviours during the day. I realize sleep training may help mom get the sleep and stop suffering and that’s why in the original article I said I thought sleep training was the lesser of two evils, but I firmly believe we shouldn’t be pitting mom against baby, but instead work to find ways to help mom with PPD without resorting to sleep training.

            While you talk of success stories, I am aware of far more negative outcomes associated with CIO (though I fully acknowledge it’s most likely due to the circles I travel in). Parents speaking of the damage done to their relationship with their child and their child’s behaviour. This is also where I think that child temperament and characteristics are going to be huge. Do I think CIO will damage all children? No (though I still don’t agree with the message it sends at such a young age). But I do think there are high-needs or highly-sensitive children where it can cause an extreme amount of damage and so we need to be very careful promoting it as being appropriate for all children and families.

            As for the idea that it means you never adapt, that’s just silly. Of course we change and adapt, but doing so at the pace your child can handle and forcing something that is traumatic and not part of what they evolved to handle are different things. We sadly live in a very adult-centric world and we fail to consider the biological needs of children. I think if we had more respect for the developmental process, many of the newer practices we find in Western society would fall by the wayside. (Which includes the reliance on daycare as we know it here – the move away from family to care for a child is a sad state we live in and something I do not like seeing. It’s a necessity but not a good one in my opinion.)

            All that said, I appreciate your interest and you voicing your opinion. I have no problem with people disagreeing with anything I write or conclude :)

  3. Jespren says

    To me this is just another ‘water is wet’ topics. Are there studies being done on CIO and possible dangers/damages? Yes. Now can someone please explain why we need a study, with all it’s intrinsic limitations, to tell us that ignoring a baby’s only way to communicate is wrong? Dress it up however you like: mom needs sleep, baby needs more/better/longer/at this specific time sleep, crying doesn’t ‘hurt’ baby, baby needs to grow up, develope, learn etc. It all comes down to the same bottom line. Baby is saying, in the only way possible “mom, I need you!” And mom is saying “I’m ignoring you right now.”
    Sorry, I don’t need a study to tell me that isn’t a good idea.

    • says

      Wholeheartedly agree, but sadly people seem to want science to tell them it’s wrong! I think we’ve gone so far down the line of ignoring our instincts that we just don’t consider them anymore, or consider them as beneath rational thought.

  4. says

    Tracy, I love how calmy and rationally you discuss this topic with the commenters on this post! And I appreciate their respectful methods of disagreement. This is the sanest discussion of CIO studies I have see , and I have greatly enjoyed reading about it. To me, it comes down to my gut feelings. We didn’t do CIO with my baby because it felt wrong to leave him alone when he was crying and my whole being was telling me to comfort him. Now that he’s older (11 months) we challenge him a little bit to fall asleep in his crib instead of nursing, or with his dad instead of me – and actually, he himself has initiated some of these changes! It’s slow going, and I’m still up a fair bit during the night, but I feel good knowing we are working together and I’m confident he’ll sleep through the night when he’s ready

  5. Kat says

    Hi Tracy, Thanks for providing such in-depth analysis regarding research on CIO. As a mama who doesn’t let my baby cry it out because it feels wrong intuitively on every level, I have had comments from advocates of sleep training that it would take a staggering amount of time of CIO before negative physiological effects were to take place (cortisol release). So my question is: How much time was the babies studied crying for until they had a large cortisol release? I have tried searching online, but have never come across any actual time frames – just more broad statements like ‘prolonged’.

    Thanks for your time!

    • says

      It depends on what your friends are looking for. You can see cortisol spikes in children within 10-20 minutes of crying alone. It can be immediate if there’s fear or another process causing stress. Much of the issue is whether or not this type of stress is enough to cause problems and to that, there isn’t a conclusive amount. It will depend on child temperametemperame, overall parenting, etc. However, if you read the piece I did on why any of this cortisol matters, you’ll see that we are adapted to control this release of cortisol by offering comfort. For the brain, this comfort is what’s needed to thrive.


  1. […] 7. Middlemiss W., et al. (2012). “Asynchrony of mother-infant hypothalamic-pituitary-adrenal axis activity following extinction of infant crying responses induced during the transition to sleep.” Early Hum Dev 88(4): 227-232;  A letter submitted to the editor criticized the broad conclusions being made from this study. Middlemiss et al responded that their study is early in the field and small, not conclusive but still offering early insights into dissociation between behavior (babies that stop crying) and physiology (continued elevations in cortisol). I also found two blog posts of interest, one citing problems with the study, and another describing areas of validity. […]

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