New research from Australia is making international headlines telling parents that they have "proven" that one form of extinction sleep training – graduated extinction or "controlled crying" – is totally, utterly safe for children. The research, out in advance release from the journal Pediatrics, claims to have found that children who undergo controlled crying do not suffer any cortisol spikes and do not show any behavioural or attachment problems later on. Unfortunately, this isn't quite the truth and a thorough look at the study is warranted so let's get on with this, shall we?
The participants were 43 families of children aged 6 months to 16 months. Families were recruited if they reported that they believed their children had a "sleep problem". Though this limits applicability, it is also relevant as most people will not attempt sleep training if they do not believe their child has a sleep problem. However, it is also worth noting that there were no objective measures of sleep problems. We have some socio-economic status data for the families, but no information on any other family factors (will get to this below).
The families were randomly assigned to one of three groups:
Families were aware this was a random assignment and two families switched groups (ethically they had to be allowed to do so): One from graduated extinction to control and one from control to graduated extinction. It is believed that the families remained true to their group given the nature of the study they agreed to. Generally this method is sound. They can't fully randomly assign people and keep them there, though the moment people asked to switch they likely should have been removed from the study as it suggests a bias of some sort towards one method over another.
Yes, 43 is small, especially when split into three groups. However, small samples are not inherently a problem, but there are issues with small samples here if we want to make any definitive conclusions. Small samples will only detect large effects. In the case of long-term effects of extinction methods, most people do not argue that every child will suffer negative effects, but likely some will. Small samples will not allow for any nuance or small effects to be detected and would not allow for any analysis of interacting variables, such as temperament or health factors.
Thus, the authors only have the power to detect a very large effect between graduated extinction and the control group. If that effect is not detected, it does not mean that there are no differences, it simply means there aren't incredibly large differences. To put it in perspective, this is the type of sample size that is used when looking for language differences – findings that are incredibly robust because each child is expected to behave the same way in learning a language.
For the initial test and the final follow-up 12 months later, the retention rate was perfect, at 100%, though they are missing data for other reasons at that 12 month follow-up. However, for the follow-ups in between – in which cortisol assessments and sleep data were recorded– there was a loss of nearly 50% of participants and no information is given as to why. This is a problem as it means the data on cortisol and infant sleep is based on the tiniest of samples and does not explain why we are missing data from nearly 50% of participants.
There were several outcome variables of interest and definitely some questions about some of the validity of assessment:
In terms of what is assessed here as outcome variables, this is pretty darn good, except for a couple things. First, there's no baseline for attachment or child behaviour by which we can see any change. This means we have no idea if sleep training or not sleep training affects anything. Second, we are missing a ton of relevant data that would better inform on whether there are interactions or nuances to any findings. This includes, but is not limited to, feeding method, how responsive and sensitive parents were outside of nighttime, child temperament, sleeping arrangements, and daycare use (which is known to influence daytime cortisol levels). This is a lot and why one must add "preliminary" to the research and findings.
The authors of this paper – and the press picking up on it – seem to have a story to be told. Namely, children who are exposed to graduated extinction will not suffer any stress as a result, will learn to sleep better, moms are happier, and children will suffer no long-term consequences of this technique. The authors argue their data conclusively shows this, but even if we ignore the small sample size (where sleep is being assessed by a total of 7 participants in each group), does it?
As you can see, the data that the authors present doesn't really support the conclusions they and the media are spouting about graduated extinction. The data does reinforce the difference between parent report sleep data and objective data, something that is showing up in other studies as well, but does it tell us anything else?
I think the big highlight of this study is the potential effectiveness of the bedtime fading strategy in combating maternal negative emotions and perceived infant sleep problems. However, as there were many issues with the data at hand, more is clearly needed to make any real conclusions about this method. Yet, this is a gentle method that in this preliminary sense provided improvement in maternal mood and lowered sleep onset latency times in line with that of graduated extinction, but without any risk of stress and no potential effect on attachment. I truly hope to see more research on this and if this becomes the go-to of families instead of extinction methods.
I actually think this methodology provides great ideas as a starting point for future research. This was a preliminary study and shouldn't have gotten the type of press it has, but that doesn't mean the methods are all bad, just lacking. I do, however, disagree strongly with the conclusions of the authors and the way in which they have presented their research to the press and public. I find that highly irresponsible and it does a huge disservice to both science and, more importantly, the babies that are left to cry. Whether an individual baby suffers long-term or not, they suffer acutely and for this to be ignored in order to promote the idea of self-soothing (which the authors erroneously do) or even for maternal well-being now that other methods seem better in that regard is just plain wrong. Families look to the press and the researchers to accurately represent research and this has not happened in this case. For that, shame on them.
However, I also want to mention something else that should be spoken of that is highlighted by this study: the surprising and disturbing bit of information regarding the low rates of secure attachment. Across the entire sample that provided attachment data, only 58% were securely attached. This is not okay and if this doesn't signal that something is going very wrong as a society – regardless of what sleep training we take part in – than I don't know what will. Most people assume that secure attachment comes so long as there's no neglect or abuse. What this is telling us (or reminding us as there has been other research showing a similar number) is that this is not the case. Our parenting practices as a whole have shifted towards such disengagement that children who are not being maltreated in any blatantly noticeable way are still insecurely attached. Given the myriad of negative outcomes associated with insecure attachment, I would hope this serves as another wake-up call to all of us to figure out a better way of raising our children.
With that, I hope for better societal support for families and a return to parenting practices that focus on the connection between parent and child. Only then do I think we can turn this around and help avoid a society run by individuals who struggle because of their upbringings.