Sleep training and cortisol

Sleep training, cortisol & stressed out babies...?

Jan 26, 2022
6 min read

I read an interesting article recently that was analysing different research on infant stress and cortisol levels, particularly in regards to "sleep training". 

Now, I don't actually like the name "sleep training". The "training" part of it makes the term sound unnatural and regimented. For the sake of this article I will call it sleep training though, because despite sleep training having a lot of connotations and interpretations, it generally just means a baby is learning the skill of falling asleep independently when they are developmentally ready to. This can be achieved through many many methods and there are countless arguments on either side of the sleep training fence - some are vehemently opposed to it and some aren't. A lot of the opposing views stem from a general misunderstanding about what sleep training actually means. By many, sleep training is viewed as being totally cry-based, as a parent abandoning their child to cry alone until they give up and fall asleep. Words like "cry-it-out" or "extinction" or "Ferber" feature here, however there are many many different forms of sleep training and they don't have to involve crying. (See HERE for more info).

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But what I want to focus on in this article is negating the broad claims that any form of sleep-training causes immense stress to a baby due to elevated cortisol levels, leading to emotional damage and long-term brain damage.

In actual fact, a good friend of mine was told this recently by a health practitioner who I can only describe as being incredibly misinformed, judgemental, old-fashioned and just plain wrong.

Lets go back to this research I'd read which focuses mainly on cortisol, the "stress hormone". Cortisol, despite it's (over-embellished) reputation as being extremely damaging for us, is a hormone that naturally features in our everyday lives. It isn't just related to profound stress and what I find most interesting is that studies have revealed the ways babies respond to different forms of stress and not all crying leads to a rise in cortisol levels. Also, not all cortisol elevations are necessarily bad or sustained. A baby will experience a rise in cortisol when something new or unexpected happens, like a newborn baby having a bath, or having their diaper changed, or a baby receiving an immunisation; this is why young babies often cry when being put in the bath or while being changed. We're certainly not going to stop bathing or changing our babies because it elevates their cortisol levels are we?! What ends up happening is that after a few days, babies do not react to the bath with a stress/cortisol response. This isn't because they've "given up crying" but simply because they have learnt from the experience and have moved through the stress response to a positive response.

Cortisol is not always the enemy we think it is.

In fact, it is a naturally released hormone as part of our circadian rhythm and studies have found that the levels of cortisol a baby releases during times of short term "stress" are lower (by 100-200%) than the cortisol levels babies (and adults) naturally produce throughout the course of each day as part of our body clock cycle. Cortisol is far higher too in babies and children who are overtired, than those who experience some form of sleep training.

 Furthermore, and this is super interesting, researchers have found that there is more sustained elevated cortisol in a child from an experience such as starting daycare, than there is after a few days of "sleep training". And this is referring to very traditional cry-it-out sleep training too (which we don't use in our Sleep Programs). I'm sure we can all agree that no one claims starting daycare can cause "permanent brain damage" or an "abandoned emotionally-crippled child" and yet, these are the phrases bandied around by sleep training scare-mongers.

No one likes hearing their baby cry, however crying doesn't mean your baby is being damaged each time they do it; that would be an extremely anti-survival outcome. The human race would not have survived if each time a baby cried they were being emotionally or mentally injured. Our countenances are not that delicate. By the time you have more than one child, you often have no choice but to let your baby cry at certain times - imagine this scenario: your toddler is toilet training and needs to go to the toilet (with your help) but your baby is tired and has started crying. You cannot leave the toddler to wet herself so you can comfort the baby, when you know the baby is actually fine, just tired. Of course you help the toddler and the baby just has to wait. These sorts of situations are commonplace when you have more than one child; our babies are not suffering long-term brain damage from being the youngest child and crying more often than their older sibling had to.

So yes, during a period of changing a baby's sleep habits there can be some crying, even with the gentlest methods - of course your baby is going to protest any change to the status quo! They are not protesting because they're traumatised, just because they are tired and want to go to sleep, but now the situation for sleep is a bit different and unexpected.

My 6 year old still responds like this. Almost every Sunday we have pancakes for breakfast, but occasionally, we don't. She wakes each Sunday expecting pancakes and if I tell her we're not having them that day, she cries and cries, she is genuinely devastated because it's not what she expected; it's different to the usual routine. To be honest, it must be quite confusing for her and it's unfair on my part because it occurs so inconsistently. If I decided we weren't having pancakes ever again on a Sunday, she'd protest the change, without a doubt, for a couple of Sundays, but then the no-pancakes would become the norm.

Protesting unexpected change is part of being human.

Your baby, in the context of a loving and responsive family environment, is not going to be placed under intense or irrevocable stress from a few days of guiding them towards new sleep habits. Even if you are using a cry-based method (and everyone is free to choose what they think is best for their family without judgement), your baby is not going to be damaged, your relationship with your baby is not going to be damaged, your baby is not going to learn that there is no one to comfort them... and how can you tell? Because I can guarantee you your baby will continue to cry for their needs to be met at other times during the day. They will still cry when they're hungry, when they're upset, when they're tired, when they're hurt. They will, however, most likely stop crying when going to sleep and that is because they've moved through the experience to form a positive response. They've learnt the new skill, it's not different or dramatic or unexpected for them anymore; it's just sleep and sleep is not complicated.

Sleep training does not exclusively mean cry-it-out. Sleep training does not mean you are causing your baby brain damage. Working gradually towards better sleep is, in the short and long term, going to mean your baby is in fact producing less cortisol overall than a baby who continues to be overtired or sleep deprived.

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"Two days in and you guys have changed my life!!!! I've been battling anywhere between 4-6 wake ups a night for over a MONTH! One day on the Program and she went down without a hassle at 7 PM (when I would previously have to rock for an hour or two). Many, many thanks! I'm seeing so much promise here and my baby is actually happier and less fussy today. The best part? Little to NO crying for us! I'm so glad I gave this Program a try over traditional sleep training methods. Babe and I are so happy." - Jamie 

"Less than a week into implementing the information from the Sleep Program, my little one was falling asleep by herself and staying asleep. This transformation took place without the need to let my baby 'cry it out'. I cannot recommend this Program enough. Buying this will literally change your life!" - Courtney 

"What I particularly love about the Little Ones strategies are that they are a more gentle alternative and can be tailored to your family so that you really see positive change to your baby's sleep. I am blown away by their comprehensive body of work." - Kate Johnson, Ph.D Sleep Physiology





Original Article: 


Shonkoff, J.P. and A.S. Garner. The lifelong effects of early childhood adversity and toxic stress. Pediatrics. 129(1): p. e232-46. 2012.

de Weerth, C., R.H. Zijl, and J.K. Buitelaar. Development of cortisol circadian rhythm in infancy. Early Hum Dev. 73(1-2): p. 39-52. 2003.

Gunnar, M.R. and B. Donzella. Social regulation of the cortisol levels in early human development. Psychoneuroendocrinology. 27(1-2): p. 199-220. 2002.

Gunnar, M.R., N.M. Talge, and A. Herrera. Stressor paradigms in developmental studies: what does and does not work to produce mean increases in salivary cortisol. Psychoneuroendocrinology. 34(7): p. 953-67. 2009.

Ahnert, L., M.R. Gunnar, M.E. Lamb, and M. Barthel. Transition to child care: associations with infant-mother attachment, infant negative emotion, and cortisol elevations. Child Dev. 75(3): p. 639-50. 2004.

Vermeer, H.J. and M.H. van IJzendoorn. Children’s elevated cortisol levels at daycare: A review and meta-analysis. Early Childhood Research Quarterly. 21: p. 390-401. 2006

Scher, A., W.A. Hall, A. Zaidman-Zait, and J. Weinberg. Sleep quality, cortisol levels, and behavioral regulation in toddlers. Dev Psychobiol. 52(1): p. 44-53. 2010.

Karraker, K.H. and M. Young. Night Waking in 6-Month-Old Infants and Maternal Depressive Symptoms. J Appl Dev Psychol. 28(5-6): p. 493-498. 2007.

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