Earlier in the week, we presented Part 1 of a commentary from Kathleen Kendall-Tackett on a recent study about the long-term effects of controlled-crying for infants. As infant sleep and breastfeeding are so closely tied together, we are so glad to share both Part 1 and Part 2 with our readers.
By Kathleen Kendall-Tackett, Ph.D., IBCLC, FAPA
Does Controlled Crying Cause Long-term Change to Cortisol Levels?
Critics of controlled crying have expressed concern that this technique alters infant cortisol level. To address this concern, the authors assessed the children’s cortisol levels at age 6 and found no significant difference between the intervention and control groups. Unfortunately, these findings alone do not mean lack of physiological harm. We need to look at short-term effects.
The question we need to ask is what happens to babies when their mothers do not respond to them? One way this has been studied is by examining the impact of maternal depression on infants. Maternal depression impairs mothers’ ability to respond to their infants’ cues, and raises Infant cortisol levels (Feldman et al., 2009). Even when non-response is temporary, babies still find it stressful. In the still-faced mother paradigm, mothers are asked to not respond to their infants’ cues in a laboratory setting. This research is designed to mimic the effects of maternal depression. The still-faced-mother experiments increase babies’ cortisol levels (Grant et al., 2009).
So why the concern about cortisol? Mainly, it’s this: cortisol is quite toxic to brain cells. If cortisol is elevated for short time, it likely causes no damage. But if cortisol levels are repeatedly elevated because the infants are experiencing long and repeated incidents of being ignored when they cry, it can be a problem. The brain is at its most vulnerable in the first five years, so soaking the developing brain in cortisol is not a good idea (Buss et al., 2012).
The lack of difference between the groups at age 6 does not mean lack of harm. Cortisol levels likely returned to normal in the intervening five years, unless there was ongoing adversity. Unfortunately, cortisol elevated in infancy could have still affected vulnerable brain cells, even if current levels are normal. The authors would need to use more sensitive measures to assess these potential changes.
What About Breastfeeding?
The final limitation of this study is rather stunning. Price et al. did not measure the effect of infant feeding method on sleep or maternal depression. Yet feeding method has a direct effect on both maternal sleep and postpartum depression, which are the two main factors the authors claim to address with their sleep intervention. Exclusively breastfeeding mothers get more sleep and are less likely to be depressed than their mixed- or formula-feeding counterparts (Doan, Gardiner, Gay, & Lee, 2007; Dorheim, Bondevik, Eberhard-Gran, & Bjorvatn, 2009a, 2009b; Kendall-Tackett, Cong, & Hale, 2011).
Given these findings, isn’t it strange that breastfeeding was not even enquired about? If the study was conducted in a country with low breastfeeding rates, this omission would be somewhat understandable. But it makes no sense coming from a country like Australia, which has one of the highest breastfeeding rates in the world.
So what can we take away from the Price et al. study? Should we recommend the controlled-crying technique to parents? Based on the limitations of this study, I do not recommend this approach. The sample size is small, the follow-up sample is missing the children most likely to be negatively affected, their assessment of the intervention did not account for the Hawthorne/placebo effect, they have not measured dose of the intervention, nor have they accounted for feeding method, which recent research has soundly demonstrated as being related to both variables that are of key interest: maternal fatigue and postpartum depression.
My objections to this approach are not new. When I first encountered the Price et al. study, I remembered a study that this same group of researchers published 10 years ago in the British Medical Journal demonstrating that controlled crying lessened the risk of postpartum depression (Hiscock & Wake, 2002). I was specifically struck by this response from a German physician (Perl, 2002):
“As a German, I am unhappy to find fairly undiluted ideas of militaristic Nazi infant care uncritically repeated by these Australian care providers. The Nazis understood very well the crucial effect of letting young babies cry on their future development and made this a central theme in their child care. As a scientist, I find it hard to believe that all of the results of mother-infant sleep research of the 1990s completely escaped the authors’ notice.”
In closing, Price et al. stated that organizations, such as the Australian Breastfeeding Association, were unduly negative towards controlled-crying techniques and need to update their recommendations based on more current research. Given recent findings in neuroscience, childhood trauma, breastfeeding, and maternal sleep, which are not accounted for in the Price et al. study, I’d respectfully advise the authors to do the same. I’d further urge healthcare providers who are considering recommending controlled crying to consider the limitations to the current study and alternative approaches that can meet the needs of both mother and baby.
Kathleen Kendall-Tackett, Ph.D., IBCLC, FAPA is a health psychologist and board-certified lactation consultant. She has authored or edited 22 books and more than 320 articles on family violence, postpartum depression, breastfeeding, and women’s health. Dr. Kendall-Tackett is a research associate at the Crimes against Children Research Center at the University of New Hampshire and a clinical associate professor of pediatrics at Texas Tech University School of Medicine in Amarillo, Texas. She is a Fellow of the American Psychological Association, and is president-elect of the APA Division of Trauma Psychology. You can view her website at www.KathleenKendall-Tackett.com