A SleepWell Research Review

If you’re thinking about hiring a sleep consultant, chances are you’ve looked on the internet for tips on how to get your baby to sleep better.  An internet search on infant sleep will turn up numerous articles.  Many of those articles lead parents to believe that teaching the skill of sleep will cause severe, long-term damage to their child.

The goal of SleepWell Sleep Planning is to help your whole family get the sleep you need.  Sleep deprivation leads to poor health and well-being for babies, mothers and families.  We empower our families with the science of sleep- how it works and why it’s so important.  The method is only a small part of the work we do.

In this two part series we will discuss the research on “Crying it Out” and the use of behavioural interventions in teaching babies and children the skill of sleep.  In Part One we will dispel the myths that are preventing families from getting the sleep they need.  In Part Two we will outline the research that has been done on the use of behavioural sleep interventions in infants and children.



Part One – The Myths Behind the “Crying it Out” Headlines

If you were to perform an internet search of the phrase “crying it out” you would be shocked at the headlines you would find:

“Cry it Out: The Method That Kills Baby Brain Cells”1 Huffington Post

“Dangers of ‘Crying It Out’, Damaging children and their relationships for the longterm”2 Psychology Today

“Science Says: Excessive Crying Could Be Harmful”3 Ask Dr. Sears

The truth about crying and sleep

 Myth One- When babies cry alone “their bodies and brains are flooded with adrenaline and cortisol stress hormones”. High levels of cortisol in the brain can “inhibit the development of nerve tissue in the brain, suppress growth, and depress the immune system”3 Ask Dr. Sears

  • References for this statement include studies done on developing rat pups and non-human primates. The only study of human children included a sample of 70 fifteen month olds studied before, during, and after their transition to child care.4 Salivary cortisol levels were tested at all three stages and findings indicated that insecure infants had higher cortisol levels than secure infants. Elevated cortisol levels can impair immune function and cause irreversible neuron damage but there is no evidence, as noted in this study, that elevations this small cause adverse consequences. In the end, the results of the study do not support the very misleading statement that cortisol is destroying nerve connections in the brain of the developing infant because cortisol levels this high were not even observed in this study.


Myth Two- “Stress hormone cortisol remain high in ‘cry babies’ even in the days after they have apparently learned to settle themselves. In other words, the child is still unhappy but just keeping quiet about it.”5 Daily Mail

  • In the study referenced in this article, 25 infants participated in a 5 day sleep training program that took place in a hospital setting where nurses were responsible for attending to the needs of the infants during the night.6 After day one there was no significant increase in cortisol levels from before to after the sleep routine. Even on the 3rd day of the program there was no significant change in cortisol levels. All infants settled to sleep without crying and the infants no longer showed outward signs of stress. Results of this study indicate no change in cortisol levels of the infants prior to the start of sleep training on day 1 to the end of sleep training on day 3.


Myth Three- Excessive crying could impact intellectual, emotional and social development. “Infants with excessive crying during the early months showed more difficulty controlling their emotions”.3 Ask Dr. Sears

  • The study cited in this article examined the effects of excessive crying in early infancy on the development of self-regulation.7 Procedures in this study of 115 infants included a 6 week cry diary and a 2 minute arm restraint procedure performed by a researcher in a lab setting to elicit frustration. Findings of this study indicated that excessive criers (14 of the 115 infants studied) showed higher levels of negative reactivity and lower self-regulation than typical criers. Overall the findings of this study were only relevant to 14 of 115 infants studied and the methods used in this study involved a research assistant in a laboratory setting restraining the arms of the children to elicit frustration.


So what is the sleep deprived family to take away from all of this?  The bottom line is that many of the articles posted on the internet claim that crying while learning the skill of sleep causes physical and psychological damage to babies.  Those articles are misleading and are not accurately interpreting the results of the studies they are referencing.  Also, the results of the studies referenced in these articles are based on very small sample sizes which cannot be generalized to all infants and children.  In other words, there is no solid evidence that the crying involved in teaching the skill of sleep poses any harm to babies, however, years of sleep deprivation is related to many health risks for all members of a family.  



In Part Two of this series we will look at the damaging effects of sleep deprivation on babies, mothers and families. We will also discuss the use of behavioural sleep interventions and the long term results of these interventions.



  1. Millner, D. (2011, Dec 22). Cry it out: The method that kills baby brain cells. Retrieved from http://www.huffingtonpost.com/denene-millner/cry-it-out_b_1163864.html
  2. Narvaez, D. (2011, Dec 11). Dangers of ‘Crying It Out’, Damaging children and their relationships for the longterm. Retrieved from http://www.psychologytoday.com/blog/moral-landscapes/201112/dangers-crying-it-out
  3. Sears (2013). Science says: Excessive crying could be harmful. Retrieved from http://www.askdrsears.com/topics/fussy-baby/science-says-excessive-crying-could-be-harmful
  4. Ahnert, L., Gunnar, M.R., Lamb, M.E., & Barthel, M. (2004). Transition to child care: Associations with infant-mother attachment, infant negative emotion, and cortisol elevations. Child Development, 75(3), 639-650.
  5. Macrae, F. (2012, May 24). Babies left to cry stay unhappy hours afterwards as stress hormone remains high. Retrieved from http://www.dailymail.co.uk/health/article-2149060/Babies-left-unhappy-hours-stress-hormone-remains-high.html
  6. Middlemiss, W., Granger, D.A., Goldberg, W.A., & Nathans, L. (2012). Asynchrony of mother-infant hypothalamic-pituitary-adrenal axis activity following extinction of infant crying responses induced during the transition to sleep. Early Human Development, 88, 227-232.
  7. Stifter, C.A. & Spinrad, T.L. (2002). The Effect of Excessive Crying on the Development of Emotion Regulation, Infancy, 3(2), 133-152.


Jen Dupuis, BSN, MN and Alysa Dobson, B.Ed, PDC (SPEC) are Certified Child Sleep Consultants with SleepWell Baby.  They work with families to help them get the sleep they need.  Jen and Alysa offer support to parents with children ages 4 months- 8 years old through both in home and remote consultations.  They can be contacted at jeniffer@sleepwellbaby.ca and alysa@sleepwellbaby.ca.
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