A Healthy Child Needs a Healthy Brain, A Healthy Brain Needs Healthy Sleep

A 2020 paper, by Professors Bilien and Wolke, concluded that “Contemporary practice of some parents in the United Kingdom to occasionally or often ‘leaving infant to cry it out’ during the first 6 months was not associated with adverse behavioural development and attachment at 18 months.” See Blog Posts 24 and 67.

• A 2021 criticism of this paper by Professors Davis and Kramer included:

“A lack of maternal response to crying may be associated with elevated cortisol…”. This is a false statement (Blog Posts 24 and 36).

“A sample that is too small may not be able to detect a ‘cry it out’ effect on attachment type.” That is, not enough children were studied by Bilgin and Wolke to make their conclusion.

• A 2021 response to the criticism of Davis and Kramer by Professors Bilgin and Wolke included:

“Only four studies, including ours, have been conducted to investigate the association between ‘leaving infant to cry out’ and attachment.” The original study of 26 mothers and infants (1972) revealed an association between leaving an infant to cry out and insecure infant mother attachment (1978). Subsequently, three replication studies have been conducted (2000 and 2 in 2020). “All of these three replication studies (365 mother-infant pairs) found no significant association between leaving infant to cry-it-out and infant-mother attachment”.

In contrast, it was the original study (1972) of only 26 children that did not include enough children to make any conclusions. However, Belgen and Wolke’s study of 178 mother-infant pairs was just sufficient to detect a difference between attachment classifications and yet no differences in security of attachment were found. “Thus, the evidence of no association between leaving infant to cry-it-out and attachment is based on overall 365 mother-infant pairs in three studies using contemporary parenting practices, while the only study finding an association included 26 mother-infant pairs. Thus, the substantial body of evidence shows no association with secure infant attachment.”

Also, the 26 subjects in the original study “were white, middle-class, infant-mother pairs in intact families who were contacted through pediatricians in private practices; all were stay at home mothers.  That is, its composition was highly selective, privileged without diversity, and there was no blinding and thus bias cannot be excluded. In contrast, both our and other studies used diverse and large samples and attachment ratings were made by an independent group of researchers blind to the exposure [did use cry-it-out or did not use cry-it-out] and research questions”. Determining attachment classification without knowledge of whether cry-it-out was used (blinding) is more objective than the situation where a single researcher assigns attachment classification and also knows whether or not cry-it-out was used. All researchers are all prone to biases; ‘blinding’ helps prevent biased findings.

“In conclusion, considering the evidence from three socially diverse samples compared to the original study, there is overwhelming evidence that letting a baby to cry it out a few times or even often has no adverse effects for infant-mother attachment formation during infancy. Rather, as has been shown over and over again, it is maternal sensitivity that predicts attachment security. In our study, we found that there were no differences in observed maternal sensitivity at 3 months between mothers who let their baby cry out a few times or not. Thus, leaving an infant to cry out a few times or often does not equate to insensitive parenting.”

Blog Posts 14, 17, and 57 discuss the subject of maternal sensitivity in the context of Emotional Availability.

Blog Posts 24–27, and 36 also discuss the subject of help or harm when a child is allowed to cry at night in order to learn how to sleep better at night.

My name is Marc Weissbluth and I’ve been a pediatrician since 1973. This baby sleep blog will help you create a healthy sleep schedule for your child. My baby sleep advice and sleep training will teach you how to get a baby to sleep through the night. To stay updated with my latest baby and child sleep blog posts, be sure to subscribe today.