Recently, a study was published in Sleep Medicine that left me speechless, not out of admiration but out of disgust. The title of the study is as follows:

“Can cry tolerance be increased in mothers of infants with sleep problems, and why does it matter?”

In my opinion, there are so many issues with this study, and I will explain why.

What is this study about?

The purpose of the study was to investigate whether three “emotion regulation strategies” could increase parental cry-tolerance.

In other words, they wanted to determine whether the ability to tolerate a baby’s crying, through the application of emotion regulation strategies, would impact the outcome of behavioral sleep interventions.

Study objectives

Firstly, the research question of this study is absurd.

Why would we want to increase cry tolerance? So that parents who practice “cry it out” can better handle the emotions that come with it, such as fear, feelings of despair, distress, helplessness, sadness, physical and emotional pain? The mere fact that they are looking to increase cry tolerance in parents suggests that it is necessary. But it wouldn’t be necessary if “cry it out” wasn’t used in the first place.

It’s like saying, “Let’s investigate if we can increase parents’ tolerance for pain in their hands so that spanking their children doesn’t hurt as much.”

Perception of crying

It is understandable that we feel a sense of discomfort when our children cry and we are unable to immediately respond. It is natural to feel that way, as every cell in our body resists and wants to go to our child immediately to comfort them. It is biologically and evolutionarily ingrained in our genetic imprint to react to our baby’s crying. The act of not letting your child cry serves a purpose. Without the highly effective crying detection system, our children (and other mammals) would have been noticed by predators and eaten (Newman, 2007).

Therefore, it serves an evolutionary purpose to develop a quick stress response to our infants crying as we become parents. This response activates us to “rescue” our child. It is our intrinsic characteristic to respond to the “separation call” of our child.

Changes in the parental brain

As one becomes a parent, the brain undergoes changes. Certain areas in the brains of parents are more activated than in non-parents. These are the corticolimbic areas associated with auditory perception, integration of emotionally relevant information, and empathy (Witteman et al., 2019). In other words, parents register their infants’ crying audibly, which gives them a kind of alarm signal that their child is in “distress,” and then at a more cognitive level, they decide how to respond. It’s no wonder that crying often triggers a stress response in the parent or caregiver. It is evolutionarily ingrained in us to enter a state of alertness when our child cries. No wonder that “letting a child cry” doesn’t feel right. Let’s not act as if this is something that needs to be fixed.

It’s bad enough that with the widely used ‘cry it out’ or ‘timed checks’ methods, this parental intuition is ignored, but going even further and trying to make parents develop tolerance for their baby’s crying goes completely against intrinsic biology.

In addition to the changed perception system, something else also changes when becoming a parent. An increase in oxytocin leads to more sensitive and attuned responses, improved mother-child synchrony, and affectionate touch (Gordon et al., 2017). In fathers, growth in the left hippocampus is associated with adaptation to parenthood. The more growth, the more positive adjustment to fatherhood: stronger feelings of attachment, fewer attachment problems, and lower levels of dysfunctional parent-child interaction (Saxbe et al., 2023). There is evidence from both human and animal studies that testosterone levels decrease during the transition to fatherhood, and this decrease in testosterone may support parental investment (Horrell et al., 2021; Glasper et al., 2019).

Why fight biology?

Why would you fight against these changes that make parents more sensitive and responsive and why would you want to ‘toughen up’ parents? It’s completely contradictory to the findings of decades of research that demonstrate that sensitive and responsive parenting is beneficial for a secure attachment relationship between parent and child. John Bowlby and Mary Ainsworth would likely turn in their graves if they saw this study.

Co-regulation

Of course, crying in general can evoke something in us as parents. It can be a trigger. Some parents would definitely benefit from regulation techniques to regulate their own emotions triggered by crying. But in my opinion, the goal should be for the regulated parent to be able to co-regulate.

Procedure

The techniques proposed in this study are not meant to reach that goal.

Participants were asked to listen to an audio clip of a crying baby, with or without one of the “emotion regulation techniques,” and then they were asked to raise their hand when they thought intervention was necessary. The emotion regulation techniques used were:

• Musical distraction: Participants simultaneously listened to a song of their choice from a selection of 20 songs and the crying of a baby. They were instructed to focus on the music while the baby’s crying was played at the same volume.
• Gaming: Participants played a game on their phone or gaming device and were instructed to focus on the game (sound of the game was muted) while listening to a crying baby.
• Reappraisal: Participants were instructed to listen to the baby’s crying while telling themselves “the crying is not serious and the baby is not sick or hurt, rather they are learning to self-soothe.” (sigh…)

What’s wrong with this?

First and foremost, these techniques, as applied in this manner, are not emotion regulation strategies. They are distractions, avoidant coping mechanisms, and palliative coping. And distraction does what it says, it diverts attention from the “pain,” attempting to suppress or ignore the emotion. Apart from trivializing your own emotions by doing so, you also role-model to your child that this is the way to go. That doesn’t seem very desirable, does it? The third technique completely disregards the baby’s feelings. It seems like something from a previous century when it was still believed that babies couldn’t feel pain… In essence, parents were asked to tell themselves “the baby’s crying doesn’t matter and is meaningless.”

Secondly, in my opinion, the instruction given to the participants was already quite biased. The instruction was:

“You are about to listen to short clips of a crying 6-month-old baby. The baby is described as very demanding as they require constant attention and almost never calm when alone. The baby’s parents have been trying to facilitate the development of self-soothing abilities by refraining from immediate response to their crying. Please listen carefully and indicate when you feel it is necessary to intervene by raising your hand.”

Isn’t being instructed like this being directed in a certain direction already? That it would be “better” to wait as long as possible to intervene because the baby is so “demanding” and should learn to self-sooth, and that this will be achieved by “refraining from immediate response to crying”…

And isn’t it very different to listen to your own crying baby compared to an audio clip of an unknown baby?? How would this impact response-time?

Thirdly, the techniques in the study are not used to deal with emotions in the presence of the baby but in isolation. There is no co-regulation involved. It assumes that the parent needs techniques to cope with sleep-training-related stress, but the baby, who experiences acute stress, is completely ignored. There is nothing wrong with (co)regulation for the parent themselves, but the goal should be for it to be a means of regulating the parent’s nervous system in order to be able to handle the baby’s emotion together with the baby. This allows the baby’s mirror neurons to work and register the regulated emotional state of the mother, which the baby then adopts. That is emotional co-regulation.

Fourthly, this approach assumes that babies can regulate themselves. The idea of the researchers is that if parents can better tolerate their baby’s crying, they will be less likely to respond quickly to their crying baby during sleep training, thereby helping the baby “develop self-soothing skills.” Here, you can see the incorrect assumption that babies can (learn to) regulate themselves.

Definition of a sleep problem

In addition, the study assumes that you should address ‘sleep problems’ with a behavioral intervention. However, there is another issue with this approach. The definition of a ‘sleep problem’ in this study is questionable:

• It is a subjective measure. There’s no factual measurements of the baby’s sleep, such as actigraphy; instead, it is classified based on parental reports.
• There is no consideration given to potential medical causes (sleep apnea, reflux, allergies, parasomnias, etc.). So, should we just let those babies cry?
• The definition of normal sleep is incorrect. Normal infant sleep is being pathologized. According to the criteria used in the study, a baby is classified as having a sleep problem (‘poor sleeping’) if:
  • The baby is awake for more than 30 minutes after sleep onset,
  • It takes the baby more than 30 minutes to fall asleep (sleep onset latency), or
  • The baby wakes up more than twice during the night.

With any of these symptoms occurring at least 3 times a week for a minimum of 3 months.

We know that it is normal for babies between the ages of 6-24 months (the age range in the study) to wake up frequently and be awake for a certain period during the night (Cerrato et al., 2017; Hoyniak et al., 2019; Del-Ponte et al., 2020).

Bias

The authors of this study are not insignificant figures. Both Michael Gradisar and Michal Kahn are well-known proponents of behavioral sleep training techniques (extinction and modified extinction, also known as cry-it-out and timed checks) for addressing sleep problems. With this study, the authors seek support to justify their own advocated methods. This is quite biased and concerning, considering the probable reach of the study.

What were the findings?

Apart from all the aforementioned objections, it was found that the cry-tolerance of mothers with ‘poor sleepers’ did not differ significantly from that of ‘good sleepers’ or mothers without children. The first group had a cry-tolerance of 60.5 seconds, the second group 60.1 seconds, and the third group 84.2 seconds. All three emotion regulation strategies resulted in higher cry-tolerance. The authors argue that the use of emotion regulation strategies can help improve the outcomes of behavioral sleep interventions. In other words (my words): If parents use techniques to suppress, avoid, or ignore their own emotions and minimize their anxious thoughts and concerns, they can tolerate their child’s crying for a longer duration, thereby waiting longer to respond to their child, which helps the child learn more quickly that signaling is futile. As a result, the parent believes that the (silenced) baby is sleeping better, leading to better outcomes of sleep training.

Conclusion:

In my opinion, the title of this study could be changed to: “Why should we even think about increasing parental cry-tolerance to serve the means of tolerating sleep training related aversion?”

References:

Ceratto, S., Dalmasso, P., Miniero, R., Cordero Di Montezemolo, L., & Savino, F. (2017). Comparison between actigraphy and parental reporting for sleep assessment in hospitalized infants. Minerva pediatrica.

Del-Ponte, B., Xavier, M. O., Bassani, D. G., Tovo-Rodrigues, L., Halal, C. S., Shionuma, A. H., … & Santos, I. S. (2020). Validity of the brief infant sleep questionnaire (BISQ) in Brazilian children. Sleep medicine, 69, 65-70.

Glasper, E. R., Kenkel, W. M., Bick, J., & Rilling, J. K. (2019). More than just mothers: The neurobiological and neuroendocrine underpinnings of allomaternal caregiving. Frontiers in Neuroendocrinology, 53, 100741.

Gordon, I., Pratt, M., Bergunde, K., Zagoory-Sharon, O., & Feldman, R. (2017). Testosterone, oxytocin, and the development of human parental care. Hormones and behavior, 93, 184-192.

Horrell, N. D., Acosta, M. C., & Saltzman, W. (2021). Plasticity of the paternal brain: Effects of fatherhood on neural structure and function. Developmental psychobiology, 63(5), 1499-1520.

Hoyniak, C. P., Bates, J. E., Staples, A. D., Rudasill, K. M., Molfese, D. L., & Molfese, V. J. (2019). Child sleep and socioeconomic context in the development of cognitive abilities in early childhood. Child development, 90(5), 1718-1737.

Newman, J. D. (2007). Neural circuits underlying crying and cry responding in mammals. Behavioural brain research, 182(2), 155-165.

Saxbe, D., Martínez‐Garcia, M., Cardenas, S. I., Waizman, Y., & Carmona, S. (2023). Changes in left hippocampal volume in first‐time fathers: Associations with oxytocin, testosterone, and adaptation to parenthood. Journal of Neuroendocrinology, e13270.

Whittall, H., Gradisar, M., Fitton, J., Pillion, M., & Kahn, M. (2023). Can cry tolerance be increased in mothers of infants with sleep problems, and why does it matter? A quasi-experimental study. Sleep Medicine.

Witteman, J., Van IJzendoorn, M. H., Rilling, J. K., Bos, P. A., Schiller, N. O., & Bakermans-Kranenburg, M. J. (2019). Towards a neural model of infant cry perception. Neuroscience & Biobehavioral Reviews, 99, 23-32.