Cry it out is a hotly debated topic, and one I have commented on previously. I make no secret of my dislike for this approach, but my dislike is based on an objective assessment. Here’s the latest study to throw into the mix… I originally posted this response on a Facebook post, but so many people wanted to be able to share it, that I have added it to my permanent blogs for ease of access.

Response to Bilgin & Wolke (2020) Parental use of ‘cry it out’ in infants: no adverse effects on attachment and behavioural development at 18 months, in The Journal of Child Psychology and Psychiatry.

The above study was a sample of 178 infants, including 73 very preterm or low birth weight infants and their caregivers. There was good retention of study subjects throughout the 18 month study. Confounding variables such as whether the infant was in the parent’s bedroom, breastfeeding status, parental income, level of education, number of children at home and parental age were mentioned, though race and ethnicity were not. Bed-sharing was also not mentioned, and of note, a significant number of infants were not sleeping in the parental bedroom at 0, 3, and 6 months, when the current guidelines clearly state that infants should be in the same room as their parents for at least the first 6 months.

Study background

The study comments on an older paper by Bell and Ainsworth (1972) which found that the more infants were left to cry, the more they cried in later infancy and early toddlerhood. This was a small sample (of 26 children) and the present study notes that this research has not been repeated.

Aim of the study

The study had 2 objectives:
1. To explore the link between frequency of leaving infants to CIO anytime in the day at 0, 3, and 6 months, and the duration and frequency of crying at 3, 6, and 18 months
2. The establish whether there is a link between frequency of CIO and behaviour and attachment issues at 18 months


In this study, parents were asked about whether they ever left their baby to cry, and this was recorded by time of day – morning, afternoon, evening and night (although this breakdown of time period is not available). Parents recorded whether their baby was left to cry:
• Never
• Once
• A few times
• Often
The researchers found that very few parents left their baby to cry once, so ‘never’ and ‘once’ was combined. It was found that 63% of parents never left their newborn to cry, whereas by 6 months, 52% left their baby to cry a few times, and at 18 months, 31% of parents left their child to cry often. The study found that infants who were left to cry a few times in the newborn period were less likely to cry at 18 months.

**It is not clear what the definition of ‘few’ and ‘often’ is, and how long the crying lasted when the infants were crying. It is also not clear what the context was – for example, was the infant left to cry in a car seat during an unavoidable car trip? Was the infant left to cry while a parent dealt with boiling hot food, took a shower, or was it in the context of trying to sleep train. This is important missing data.

At 3 and 18 months, maternal sensitivity was measured, and at 18 months, the Strange Situation test and a validated behavioural observation tool was used to assess play and behaviour.


The study found that leaving infants to cry it out in the newborn period was weakly associated with less crying at 3 months, and more convincingly correlated with reduced crying at 18 months. However, only a small minority of parents left their child to cry it out ‘often’ as newborns. 60% of all parents never left their child to cry at this time point, so the number of infants that this applies to is small. Nevertheless, it seems to suggest the opposite of the Bell and Ainsworth study which found that more crying in infancy is associated with more crying later on.
The study also found that more episodes of leaving infants to cry it out was not associated with behaviour problems or insecure attachment.


1. This study was not aiming to make recommendations about whether cry it out should be used as a strategy or not. It was simply exploring the association between cry it out and later frequency of crying, as well as effect on attachment.
2. The study in fact concludes that intuitive and adaptive parenting is recommended.
3. The study did not clearly differentiate between amounts of crying in one episode. It asked parents about how often they left their baby to cry, but not how long their infant cried when they were left.
4. The researchers did not define what they meant by a ‘few times’ or ‘often’, when asking parents how often they left their child to cry. This is important – was it every day? Every sleep opportunity? Once a week? Inconsistently according to when there were no other options? There are a lot of unanswered questions in this regard.
5. The study did not discuss the different reasons why babies might be left to cry – for example, if a parent could not respond immediately because they were busy.
6. There was no discussion about when babies were mostly left crying. The parents were asked to state the time of day of the crying, but this data is not explored in the paper. This is important, because many people will read this study through a ‘sleep training’ lens, but actually the study was asking about crying at other times of day. It would have been helpful to know if the crying was only in the context of sleep (i.e. naps, bedtime and through the night) or if it was at times not associated with sleep.
7. It is not clear whether the same children were left crying at multiple time points. This is also important missing data because some children cry more than others. It would be useful to know whether the cry it out was repeated at multiple time points, because it did not have a long term effect, or whether once the children were left to cry, they no longer exhibited this behaviour.
8. The study did not measure cortisol values over time.
9. The study did not control for factors that are known to increase infant reactivity and crying in the neonatal period – such as prenatal stress, and higher maternal cortisol.
10. The study used the Strange Situation test at 18 months. However, some of the infants were left to cry at 18 months. It is not clear whether these infants had been left to cry before this time point, or if this was the first episode of crying. If it was the first, it would be difficult to assess for whether the intervention had had an impact on behaviour, and attachment.
11. There is no control or comment on parental mental health. The researchers later mention a hypothesised link between leaving infants to cry and improved mental health, but they do not account for whether the parents in this sample had mental health problems.
12. The attachment coding is not available as a data set. It is known that a proportion of the population will be coded as insecure, but it would have been nice to see the breakdown of coding of attachment type within the data, to be able to comment on this.
13. There is no discussion of infant temperament. The children were assessed at 18 months, and aspects of behaviour were noted. But arguably, these are inherited characteristics – such as persistence in activities, tendency towards more movement and hyperactivity, and attention to tasks. There are too many confounding variables to use this as an association between cry it out and the direct impact on behaviour.
14. There is no comment on normal sleep, sleep education, settling techniques, or parent education on how to soothe babies. It is not known whether the parents left their babies to cry because they had no other strategies to draw upon, i.e. they had already tried other strategies and were at their wits end, or was this a calm, rational decision to leave their infant to cry.
15. There is no discussion of why parents left their infants to cry in the first place. Was it because the parents felt they should? Was it because they had been advised to do this? Did they read books?
16. It is unclear exactly how the samples were recruited. It is also not clear whether this was a slightly self-selecting sample of people interested in sleep, settling and crying.
17. There are a significant number of babies who were not in the parental bedroom in the first 6 months (24% at 0 months, 42% at 3 months, 86% at 6 months). There is no comment on the fact that this is not considered best practice, why this was happening, and how this compares with national data.
18. The authors comment that more babies cry in the early weeks irrespective of whether they are promptly attended to or not, and crying generally diminishes over time. How much this trend may explain some of the reduction in crying is unclear, as the number of babies left to cry frequently from a very young age was small, and the association between leaving to cry in the newborn period and crying at 3 months was weak.
19. The researchers position leaving to cry as a form of limit setting, within authoritative parenting. This has not been researched though, so it is important not to assume that leaving babies to cry falls within the parameters of what everyone perceives as authoritative parenting.
20. There is no clear definition of what the authors mean by self-soothing. There are a number of ways to interpret this phrase. Thomas Anders coined this in his 1979 paper which found that some infants were able to return to sleep between sleep cycles without needing help, while other babies could not, and instead ‘signalled’ to their parents. There has not been enough research to work out what the differences in these two types of infant are. Or do they mean leaving to cry until an infant has stopped signalling. Or finally, do they mean emotional regulation, which is widely felt to be unrealistic in very young infants, due to the immaturity of their prefrontal cortex.
21. The authors suggest that leaving infants to cry gives them an opportunity to self soothe by exploring ways to achieve a sense of self and manage their behavioural state regulation. However, there is no consistent evidence that all infants are universally able to do this. Some studies suggest that infants do stop signalling, but that they have not in fact self-soothed.
22. There is no evidence that leaving a baby to cry will help them to manage their autonomic behavioural state. Some babies do have strategies that they can recruit to become calm (such as bringing their hands to their mouths), while others need more parental intervention. Leaving the former baby to cry is likely to be less harmful than the latter, but it is unwise to suggest that all babies will be able to manage their state regulation equally.


This was a larger study aiming to explore the links between the frequency of crying in early and later infancy, as well as the impact of leaving to cry and later attachment. The study is not making any recommendations about whether parents should leave their children to cry. The study was also not specifically about sleep training, so care should be taken not to assume the context of the crying explored in the study. There are many unanswered questions that prevent a more conclusive response about crying.
It is clear that many parents do sometimes have to leave their children to cry (for example if they are in a car seat, or while they attend to urgent or dangerous tasks). In this respect, it is reassuring that occasional episodes of leaving to cry was not associated with long term harm. However, the parameters were not clearly defined in this study, so it is difficult to make firm conclusions about how much crying, how often and the context of crying.

The study also makes it clear that leaving a child to cry may not be associated with neglectful parenting, but may be used in the context of a responsive, loving home environment. However, it is concerning that because of the lack of firm parameters, and the lack of control for factors such as mental health problems it would be difficult to conclusively reassure parents that leaving their infant to cry is a safe thing to do.
There is also no mention of the fact that many parents simply want to pursue less stressful strategies, preferring to respond to their child because it feels instinctively like the right thing to do.

It is concerning that this study may be taken out of context, as indeed it already has appeared to have done in the media. Parenting does indeed bring many stresses and challenges, and a crying baby, sleep deprivation and adapting to the needs of a small child are difficult, especially in the context of limited social support.

We would urge parents to seek support from a suitably trained professional who is able to support them to observe their infant’s individual cues and respond accordingly, rather than be falsely reassured that leaving their infant to cry is a safe strategy.

Lyndsey Hookway is a paediatric nurse, health visitor, IBCLC, birth trauma recovery practitioner and holistic sleep and behaviour coach, and is also a respected International speaker and the Co-founder and Clinical Director of the Holistic Sleep Coaching Program. You can pLyndsey Hookway is a paediatric nurse, health visitor, IBCLC, holistic sleep coach, PhD researcher, international speaker and author of 3 books. Lyndsey is also the Co-founder and Clinical Director of the Holistic Sleep Coaching Program, co-founder of the Thought Rebellion, and founder of the Breastfeeding the Brave project. Check Lyndsey’s speaker bio and talk brochure, as well as book her to speak at your event by visiting this page. All Lyndsey’s books, digital guides, courses and webinars can be purchased here, and you can also sign up for her free monthly newsletter here.