The Cry it Out Debate – Is it Safe, or Not?

It seems like every month new research is published trying to prove, or disprove, the safety of cry based infant sleep training. Each one contradicts the previous one and each one proclaims to give THE answer. I’ve fallen out of love with infant sleep research that tries to prove harm, or not, of different methods of sleep training and I now take them all with a pinch of salt. I don’t believe that there will ever be an unflawed study that will ever be able to prove the harm or safety of infant sleep training. Infant behaviour, especially sleep, is not an easily quantifiable issue, it is murky grey. There is no black and white ‘right’ answer and I truly believe that there never will be.

Here’s why I have lost faith in sleep training research:

Lack of Replicability

One study alone means very little. The results may be isolated. There is a reason why conflicting research is constantly published. Until research shows me the same results time and time again, by different researchers, I will treat it cautiously.

Sample Size

Understandably sleep research focussing on interviews, actigraphy and biomedical markers such as cortisol is going to be expensive and time consuming. Most studies therefore focus on a very small number of infants. This makes the findings less reliable.

Confirmation Bias

Scientists in this field of work tend to enter into research with a set idea of what they believe is right or wrong, often based on their own personal experiences of parenting. Unsurprisingly they tend to ‘prove’ what they believe. If they believe cry based sleep training is wrong, they tend to produce results that support their ideals, if they believe it is the right thing to do, they tend to produce results that support this too. Despite controlling for this as much as possible it undoubtedly plays a large role.

Lack of Surity of Action

Unless a scientists monitors each parent and child all night they don’t really know what they are measuring. Parents may have been given instructions to carry out a certain method of sleep training, but unless they are watched constantly the scientists have no idea of what they really did (this was a major flaw of research conducted in 2012 trying to prove sleep trainings safety). This lack of truly understanding what the parents did is only compounded by the fact that subjects tend to tell researchers what they think they want to hear.

The Ability to Quantify Infant Sleep

Infant sleep is ever changing. Month by month it does not look the same. Sleep changes by age, by location, with physical and psychological developments, with parents going back to work, with the introduction of solids, or with parental stress levels. We do not know what works at any particular time and in consideration of all variable. Just like adults, babies will have good days and bad, tricky sleep and easy sleep. Most sleep research is just a snapshot into their lives. What works and is safe, or unsafe today may not apply tomorrow.

The Inability to Prove Long Term Harm or Safety

Research into infant sleep concentrates on the very short term. Does it cause harm instantly or in a year or two down the line? What about ten, fifteen, twenty years down the line? No longitudinal research exists here. Who knows what will happen to the babies trained with cry based sleep training when they are adults. What effect will their upbringing have upon their relationships and indeed their own parenting. We just don’t know and until we do, we cannot say whether something is harmful or safe.

What we also do not know is the long term neurological effects of sleep training. What effects, if any, does it have on brain architecture? Measured long term. This of course will never happen. Large scale, long term MRIs are prohibitively expensive and time consuming. This is what is needed however to prove, or disprove, harm.

Parental Self Reporting

Most sleep research relies on parents to report their opinions of their child’s emotional state. At best the Ainsworth strange situation may be applied, but in most cases attachment and ill effects are assessed by asking the parents “do you think it negatively affected your child?”. Remembering the tendency for subjects to reply affirming the researcher, it is unlikely that any parent who knowingly agreed to put their child into the experiment would admit concerns. We must also take account of cognitive dissonance, would the parents even admit any potential harm to themselves?

The Inability to Prove Long Term Efficacy

Just as none of the research can prove long term safety, they also cannot confirm long term efficacy. As mentioned previously, infant sleep is not linear, it regresses as often as it improves. The effects of any intervention need to be monitored within a few days, a few weeks, a few months and a few years. Otherwise we have no idea whether any positive effect will continue and indeed whether it will produce negative sleep effects in the months and years to come after any initial improvement.

Quantifying Attachment and Emotional Stability

These are two concepts that are almost impossible to prove in infancy beyond educated guesses based on old techniques of measurement. Attachment, just like infant sleep, is almost impossible to quantify. Even if it was, what about the future effects and the development of independence and confidence years later? We have no idea of the effects of these.

The Reliability of Salivary Cortisol

Isn’t it ironic that in some cases the reliability of salivary cortisol is called into question (I’m talking the Middlemiss 2012 research), yet when it is used to support sleep training and supposed lack of problems it is freely accepted as ‘proof’ that it is safe and effective. Double standards anyone?

For those wondering, the reliability of it has been called into question many times, therefore one must ask if any research using it as their only quantitative evidence is reliable.

Researching the Wrong Goal

We must ask why research focusses on getting babies to ‘sleep through the night’. All scientists must know that this does not happen, in infancy or adulthood. We all sleep in cycles and we all rouse, or come close to it, many times. What they are really measuring is how long infants do not signal to their parents that they are awake. If they don’t signal we have absolutely no way of knowing whether this is because they are calm and able to easily transition to sleep or not, or if they do not cry out because they do not expect a response. Should the real goal not be to consider ways to help parents and babies to feel more rested and happier? Focussing on reducing postnatal depression and anxiety and researching the appropriate amount of sleep acceptable on an individual basis to consider emotional and physical health in infant and child? Why does all of the research fixate on the outdated authoritarian notion of ‘sleeping through’?

A poor understanding of the reason for the effect

We will never know why sleep training encourages babies to be quiet at night. We have no way of knowing whether it solves ‘sleep problems’, or whether it encourages a lack of trust and signalling in babies. Only the babies know this.

Contradiction With Other Research

We know that frequent night waking is protective for infants when it comes to SIDS and breastfeeding at night, particularly with bedsharing, can prolong the breastfeeding relationship, which is best for babies and mothers (from a biological point of view). Research that seeks to promote sleep training professes to show no harm, yet they forget the harm caused by prematurely ceasing breastfeeding and making infants sleep in an unnaturally deep state.

Confusion for Parents

The constant changing of opinions and ‘evidence’ of sleep training is confusing for parents. In fact they would be better with no research at all. Those who cry based sleep train because current research says it is safe will question their choice and feel guilt when the next study ‘proves’ it to be dangerous. Those who don’t sleep train will now be questioning their choices, particularly if they are in an vulnerable exhausted state. This research serves only to induce guilt,  confusion, stress and worry in parents, despite the researchers’ best intentions.

Gross assumptions by the researchers

Taking all of these issues into account, we must question the sweeping statements made by the researchers, keen to spread their message and indeed their method far and wide. Very often however their research is inadequate to support the claims they make. Indeed speaking about research that supposedly proves that cry based sleep training is ‘safe’ researcher Michael Gradisar says “It looks like you’ve got two effective treatments that don’t necessarily lead to negative outcomes,” however he just cannot say this based on the limited research and understanding that he has from it.

So what do we know about the effect and efficacy of cry based sleep training based on current scientific evidence? The answer is ‘not a lot’. As yet we do not have any research that is reliable, replicable and indeed longitudinal. From either camp. At this present moment in time we are left in the position of just not knowing the long term effects and our understanding of the short term is shaky too. This is why I am cynical about infant sleep research and why I believe we will be in this same position for the next fifty years or more.

Until such time I prefer to look at the issues from a moral perspective. Just because we can, doesn’t mean we should. Should we sleep train babies, when they are sleeping normally (like babies) to better fit into our world?  Should we endure the stress of hearing our babies cry and not responding? Should we listen to the (often poor) advice from health professionals to sleep train?

What of our ancestors, other cultures and other mammals. Why do they not struggle with sleep the way we do? Sleep training is an incredibly modern concept by historical standards, why did it not exist more than two hundred years ago?

Until such time when definitive proof exists of no long term harm and long term benefits, we must question why we are being urged to do it, especially when it is at odds with our parenting instincts.

The NEWLY UPDATED Gentle Sleep Book – out now! If you would like to understand and learn how to improve your baby, toddler, or pre-schooler’s sleep WITHOUT cry-based conventional sleep training, this is the book for you!


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Published by SarahOckwell-Smith

Sarah Ockwell-Smith, Parenting author and mother to four.

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