Mothers SHOULD leave babies to cry, because the study says so?

"Don't get up if your baby cries at night: Mothers SHOULD leave their babies to 'self-soothe' says leading expert "

Was the Daily Mail headline.  Science Daily went for:

"Let Crying Babes Lie: Study Supports Notion of Leaving Infants to Cry Themselves Back to Sleep"

Crikey, right!  What about dads or mum's partner, can they respond?  ;-)

Let's see the evidence...

From a study of 1200 infants

"66% of the children showed a flat trajectory of sleep awakenings from 6 through 36 months, with mothers reporting their infant awakening from sleep about 1 night per week. 

The second group, labelled Transitional Sleepers, included 34% of the infants. These children had 7 reported nights of awakenings per week at 6 months, dropping to 2 nights per week at 15 months and to 1 night per week by 24 months."

To summarise, 2/3rds of babies woke once per week, 1/3 woke seven times per week. Given a whole 1/3rd continued to wake, it was hardly a tiny minority.  What is also interesting to note is that the authors used data collected in 1991, that's 20 years ago!

This is significant as there was a dip in breastfeeding initiation rates in the late 1980s, followed by a return in the mid-1990s (1); ie breastfeeding rates were low at the time of data collection.  Are we basing our "normal infant sleep" on infants fed human milk or that of another species?  No idea as the study doesn't tell us that...

It does note:

"Compared with Sleepers, Transitional Sleepers were more likely to be boys, score higher on the 6-month difficult temperament assessment, be breastfed at 6 and 15 months old, and have more depressed mothers at 6 months old."

1.  "Score higher on the 6-month difficult temperament assessment":  A parental assessment (not independently validated), the flaws of which are discussed here, in a piece that discusses why "irritability" might actually be a positive behavioural trait:

"Humans often perceive infant crying as stress, but for infant animals irritability is a normal component of signalling to parents. The expression of offspring demand is part of a dynamic signalling system between parents and offspring, and has received much attention from zoologists studying a variety of bird and mammal species."

Philip Zeskind, an associate professor of psychology states:

"Although breast-fed babies are perceived to be more irritable than bottle-fed newborns, our results suggest that the behaviors of breast-fed infants are physiologically more desirable. Feeding infants formula may make them sleep more and may disrupt the smooth running of their arousal systems."

2.  "Be breastfed at 6 and 15 months old":  Given that we know beyond any doubt human infants are supposed to receive human milk at this age, if babies wake more frequently when breastfed this is probably the norm.

3.  "and have more depressed mothers at 6 months old":  Perhaps because they're constantly being bombarded with the notion their baby should be sleeping and that it's their fault if not?  Perhaps because nobody told them 1/3rd of babies continue to wake as per normal behaviour?

Professor Marsha Weinraub, from Temple University, Philadelphia, who led the study, said in an interview:

‘When mothers tune in to these night time awakenings... then he or she may not be learning how to self-soothe, something that is critical for regular sleep.’

Anyone else wonder how long it would be before we hit those infamous words "self soothing"?

The key mantra of baby tamers everywhere, seems key to this study too.  But that in itself is rather a stumbling block, as blogger "Uncommon sense" highlights in her piece "Self-soothing. Possibly the biggest lie ever foisted on parents".

But let's run with it for the moment and assume that Weinraubs can actually provide evidence in her study that a) mothers shouldn't tune in to night time awakenings; b) if they do this disturbs the baby's learning how to self-soothe which is critical.  Where does Weinraubs say we should be leaving them to cry as per the media reports?

Furthermore, perhaps we had better a) nudge all those teenagers who were raised responsively, but now enjoy sleeping until noon! b) let mothers across the world know this ASAP.  Because as Jared Diamond, author of the book The World Until Yesterday: What can we learn from traditional societies? explains:

“A cross-cultural sample of 90 traditional human societies identified not a single one with mother and infant sleeping in separate rooms.  The current Western practice [of separate rooms for mother and child] is a recent invention responsible for the struggles at putting kids to bed that torment modern Western parents.”

And that's the interesting thing, "sleep problems" appear to be a Western phenomenon.   In fact what constitutes a sleep problem seems based upon parental expectations, rather than any sort of official criteria:

"Healthy babies cycle through sleep stages, waking several times during the night. Generally, babies soothe themselves and return to sleep without alerting their parents (Anders et al, 1992; Goodlin-Jones, Burnham, Gaylor, & Anders, 2001)
When babies are not able to return to sleep on their own, they may signal their awakening to their parents. This signaling may take the form of either crying or calling out, and it alerts the parents to the child’s awakening. 

This signaling can be disruptive to parents (Karraker & Young, 2007) and considered a sleep “problem.” Some researchers see these sleep awakenings reported by parents to be sleep continuity problems (e.g., Sadeh & Anders, 1993). Although not all parents experience infant signaling upon awakening as problematic (Karraker & Young, 2007), describing and understanding sleep awakenings poses an important challenge for developmental psychologists".

So generally babies soothe themselves and return to sleep without alerting their parents?  Which babies are these?  How were they fed?  Where did they sleep?  Had they been "trained" to sleep?  It's certainly not what many cultures expect:

In a piece entitled "Why African Babies Don't Cry: An African Perspective" by Claire Niala, one of the key tips is:

• Co-sleep. Many times you can feed your baby before they are fully awake, which will allow them to go back to sleep easier and get you more rest.

Quite!  But should we be thinking about shipping some of our best therapists to Africa, as surely nobody will learn to sleep with parenting this responsive?

I decided to get the whole paper, but quickly regretted it.

It's all based around the notion that infants calling/signalling (ie crying) to their parents at night is disruptive, and therefore a sleep problem.  Which, if a good chunk of the world expects babies to wake, would explain why we're the only ones with problems!

The study starts by considering "Intrinsic Variables Related to Sleep Awakenings" - of course based on said assumptions.

"In particular, babies who breastfeed may find it difficult to soothe themselves and return to sleep in the middle of the night because they have become accustomed to falling asleep while nursing (e.g. Karraker, 2008). Early in infancy, breastfed babies may awaken more frequently throughout the night than formulafed infants (e.g. Elias, Nicholson, Bora & Johnston, 1986) because breast milk is digested more quickly; later in infancy, breastfed infants may awaken more frequently, not because they are hungry but because they have difficulty returning to sleep without the customary nursing (Karraker, 2008; Middlemiss, 2004)."

So babies who are fed as per the biological norm may find it difficult to soothe themselves because they fall asleep when feeding.  This is in part because breastmilk delivers a nice dose of sleepy, relaxing hormones; and also because they're snuggled up warm with mum, her scent, touch and taste.  Anyone who has breastfed a baby who isn't sleepy may  have noted the eye-rolling  "milk coma" breastfeeding can induce.  So we have to stop breastfeeding?

Let's flip the language:
"Early in infancy non breastfed babies may awaken less frequently throughout the night than breastfed infants, because formula is more difficult to digest.

And this is a good thing for babies?

We then do a U-turn as authors acknowledge:

"As capacity for self-regulation in the second and third years of life increases, most children resolve their early difficulties with sleep awakening (Bronson, 2000; Tikotzky & Sadeh, 2009)."

Aaaahh right, so perhaps instead of "resolving early difficulties", they just develop normally and transition towards independence as so many other cultures expect?  Cancel the therapists!

The study goes on to say:

"Difficult temperament appears related to sleep awakenings and sleep problems in general. According to Sadeh & Anders (1993), infants who are irritable and hypersensitive and have lower sensory thresholds may sleep for shorter periods and nap irregularly. Morrell and Steele (2003) suggested that difficult infants may elicit more active parent comforting, which may perpetuate night awakenings."

So babies who have a "difficult temperament" also tend to have disturbed sleep.  Note this doesn't suggest that disturbed sleep causes the "difficult temperament", only that the two are observed together.  In practice if something is making baby irritable during the day, it can also disturb sleep; it's hardly a ground breaking revelation (as millions of parents who have soothed a teething baby know).

Next up breastfeeding:

"Several studies have associated problems with sleep awakenings with factors related to breastfeeding— being nursed to sleep, having parental presence until sleep onset, or being fed on awakening (Lam et al., 2003; Touchette et al., 2005). Elias, Nicholson, Bora, and Johnston (1986), following babies for 2 years, reported that sleep awakenings were common in breastfed infants throughout the first 2 years of life; few studies have disputed this finding."

Uh oh, several studies have found our biological norm is to feed and wake frequently, like our closest mammalian relatives and other carrying mammals :O  So, ultimately what these studies confirm is that it is normal.

What's even more interesting is the paper (the one the media claim supports leaving babies to cry!) states:

"By 18 months old, not only are Transitional Sleepers able to sleep through the night without awakening their parents, but they are indistinguishable from the children who, from the beginning, had frequently slept through the night without signaling."

But hang on, I thought this learning to self soothe and stopping "signalling" early was critical?  Yet by 18 months all children slept the same?

It continues:

"The suggestion by Morrell and Steele (2003) that difficult infants may elicit more active parent comforting that may perpetuate night awakenings does not gain support from our findings"

And

"Most studies generally show that that maternal sensitivity is related to optimal and more desirable or advanced developmental infant outcomes (Davis & Logsdon, 2011). 

Here, we found that greater sensitivity was related to more awakenings at each assessment period. Infants whose mothers display sensitivity during play and structured interactions are more likely to continue to awaken more frequently than infants whose mothers are less responsive."

So there is nothing to support the theory babies wake because they are comforted, but studies show the less responsive the mother in general, the less the baby wakes.  Furthermore, responsive parenting has been repeatedly shown to "more desirable or advanced developmental infant outcomes".

It goes on to theorise:

"One explanation may be that generally sensitive mothers during the day are also more inclined to intervene when the infant shows signs of struggling with sleep. This may support Karraker’s (2008) suggestion that when mothers attempt to assist their children in returning to sleep, their responsiveness reinforce behaviors in the child that run counter to self-soothing and self-regulation.

One counter to this interpretation is that we find this relation between infant signaling upon awakening and maternal sensitivity as early as 6 months old, a time when infants might not be as sensitive to instrumental learning as after 9 months (Bell & Ainsworth, 1972). 

Alternatively, it may be that mothers who are more sensitive are more likely to hear their children signaling upon awakening, and they are therefore more likely to report these awakenings. Their behavior may not be instrumental in interfering with children’s self-soothing at all. "

So basically they don't know?

But wait.

Where is the evidence to support the comments researcher Professor Marsha Weinraub made about self soothing?  This study doesn't give us anything beyond an observation of sleep patterns of babies 20 years ago, mixed up with some hypothesising and possible theory making?

Again, we have no idea what percentage of these infants were sleep trained, where they slept or how they were fed, which aren't the only limitations of the study as the authors themselves acknowledge:

Findings from this study are limited by their reliance on data obtained from maternal report. We have no independent measures of infants’ sleep (e.g., polysomnography or observation) other than maternal report. In addition, we did not have direct measures of sleep routines or bedtime conditions that might affect nighttime sleep awakenings.

Did I miss the section that covers leaving babies to cry it out?  It must be in the paper somewhere given the media coverage?  Perhaps it's under the conclusion of the paper, the "Practical Implications":

"These findings suggest that parents and primary health care providers should be aware that some infants who are generally healthy and typically developing might nevertheless have mothers who report sleep awakenings that extend into their infant’s second year of life. 

Those infants more predisposed to early sleep problems are also those who are reported by their mothers to have difficult temperaments and to be breastfeeding. 
However, for nearly all healthy infants, sleep awakenings tend to abate by the middle of the second year. 

Because our study mothers described infants with many awakenings per week as creating problems for themselves and other family members, parents might be encouraged to establish more nuanced, carefully targeted routines to help babies with self-soothing and to seek occasional respite (Karraker, 2008)."

In short, healthy normally developing infants can wake into the second year of life, and for most these wakings abate by the middle half of the second year.  But given parents find waking problematic they can try routines to help break the habit of their children needing them and take occasional breaks if they need to. Did we really need a study to tell us that?

Lastly something the piece doesn't consider, is that a growing body of evidence from both science and history suggests that the eight-hour sleep may be unnatural.

Roger Ekirch of Virginia Tech published a seminal paper, drawn from 16 years of research, revealing a wealth of historical evidence that humans used to sleep in two distinct chunks. A first sleep which began about two hours after dusk, followed by waking period of one or two hours and then a second sleep. References of two sleeping spells started to wane in the late 17th Century, and by 1920 had receded entirely from our social consciousness.

However this may actually be our natural way to sleep. In the early 1990's, psychiatrist Thomas Wehr conducted an experiment in which a group of people were plunged into darkness for 14 hours every day for a month.  It took some time for their sleep to regulate but by the fourth week the subjects had settled into a very distinct sleeping pattern. They slept first for four hours, then woke for one or two hours before falling into a second four-hour sleep. Read more here

Consider this in light of the above study.  Breastfed babies who were responsively parented, were more likely to wake once per night, were more likely to fit the human norm.  Do we want long sleep stretches from our babies at any cost?  

Given what we know about SIDS, the longer term impact of not responding, and the fact that in the end those who woke frequently settle into longer sleep stretches anyway  - whose needs is that actually meeting?

References:
1. The Resurgence of Breastfeeding at the End of the Second Millennium 1,2 J. Nutr. February 1, 2001vol. 131 no. 2 421S-425S