Debunking Evidence in Support of Cry-it-Out

It’s a decision most parents are faced with at some point – whether or not to sleep train their baby. I know it can be a touchy subject, and I know that parents have a number of reasons why they do or do not choose to sleep train. Although for the most part I don’t agree with leaving children to cry themselves to sleep, I do acknowledge there are situations where this method may be used effectively.

What is critical in the decision whether to sleep train and which method to use is the personality of the child. Not whether it is convenient for the parent. Not because this is “the only way” to get their child to sleep. And not because it worked for someone else’s baby. It needs to be the right match for the baby’s disposition and existing sleep skills.

Leaving babies to cry themselves to sleep can be detrimental in a number of ways. Specifically, it can:

•raise infant stress hormones, even days later when they are showing no outward signs of distress

•undermine the formation of a secure parent-child attachment bond 

•contribute to the development of long-term difficulties in regulating stress and long-term sleep issues

And yet, advice to let babies cry it out proliferates. Unfortunately, some of the evidence to support this approach is problematic. I have recently read two online articles (from reputable, popular sites) promoting cry-it-out that provide as evidence the results of a 2012 study led by Marsha Weinraub published in Developmental Psychology. One of these online articles was titled: “Study Suggests Crying it Out Helps Baby Sleep Better”.

So you may be surprised to hear that Weinraub’s study did not in any way measure cry-it-out, or any sleep training method for that matter. Instead, the study measured infant night wakings between 6 and 36 months and identified a number of variables that correlated with night wakings.

The results, if anything, show that it is completely normal for infants to wake at night. One third of all babies at 6 months were waking every night. And even better news, these waking babies eventually grew out of it. By 15 months they were waking 2 nights a week and were down to one night a week by 24 months.

The misinterpretation of results came from the correlates of night waking that were identified. At 6 months, babies were more likely to wake at night if (in addition to other variables) they were male, if they had a difficult temperament, if they were breastfed, and if their mothers scored higher on maternal sensitivity (which means that the mother responds quickly and appropriately to infant needs/distress). It was this finding, that responsive mothers had babies who woke at night, that led Weinraub to speculate that perhaps these mothers were quickly responding to any night time cries and not giving infants a chance to settle themselves to sleep. She suggested that not responding (leaving babies to cry) may result in less night waking. However, this was purely speculation because, as mentioned above, Weinraub’s study did not evaluate any form of sleep training and did not even assess whether mothers had used sleep training with their baby.
(It was also a correlational study which means that it is impossible to determine a cause and effect relationship).

Speculation is perfectly reasonable within a research report, when presented alongside the actual study results, but when these speculations are then picked up by other outlets and reported as “fact” that becomes a big problem. Particularly when we are talking about a practice that is known to be detrimental to infant development (and when parents are more likely to be reading these online articles than research reports).

Even regarding Weinraub’s interpretation there are a number of issues. The study also found that breastfeeding was related to night waking – so would she suggest that mothers forego breastfeeding in order for babies to sleep through the night? I doubt it. But then why would she suggest mothers stop being responsive and sensitive to their babies’ needs for the purposes of sleep, when research has shown over and over the critical importance of maternal sensitivity to infant development?

There are other potential explanations for the correlation found in the study, for example mothers might become more sensitive when they have babies who require it. Or it could be that the sensitive mothers in this study were those who had not yet used any form of sleep training, so their babies were still waking. While less sensitive mothers may have used cry-it-out already, and their babies were waking in distress but not crying at night (as night waking was measured through mothers’ reports not an observational measure of infants). Again, I can’t stress enough that sleep training was not a variable in this study so no conclusions whatsoever can be drawn about the effectiveness of any sleep training method.

A finding from Weinraub’s study that I think deserves greater focus is the finding that infants with a difficult temperament were more likely to wake at night. These infants have high activity levels and tend to be irregular with their sleep and feeding patterns (day and night). It doesn’t seem out of character to find that these babies are waking during the night. And many times these are the babies who need that extra help to fall asleep – whether it is the comfort of their mothers arms or a breastfeed. The sensitive mothers who are responding to these needs are helping their babies learn how to regulate their distress and fall asleep. No amount of crying is going to change a baby’s personality. Some babies just require more help with sleep than others.

And as we see in Weinraub’s study – these babies grow out of it! By 24 months, the babies who were originally waking every night were down to waking once a week and by this time difficult temperament was no longer associated with night waking. 

Cry-it-out will no doubt work for some children, those who are already on the way to being good sleepers and just need that extra push to go it alone. But there is a difference between letting a baby cry for 10 minutes before falling asleep and leaving an infant hysterically crying for 3 hours to the point of vomiting (this is literally advice given to parents). Cry-it-out is not a solution that should be touted as the gold standard in successful infant sleep, and if it is then it needs to be backed by solid research evidence not studies irrelevant to sleep training.

I would urge and remind parents to think critically about what they read and have more confidence in the fact that they (and they alone) know what is right for their own child. There is no single solution that works in every situation for every child. And I would be surprised if being less responsive to a child’s needs is ever the answer.

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