Dubious claims that crying babies 'self-soothe'

Letting an infant cry itself to sleep is the best way to ensure a good night’s rest for all, according to The Daily Telegraph, while the Daily Mail claims that ‘Mothers should leave their babies to “self-soothe” says leading expert’.

Both headlines represent a massive over-simplification of an extremely complex piece of research looking at a wide range of factors that may impact on infants’ sleep patterns. Factors examined include the child’s temperament, history of illness, whether an infant was breastfed or whether the mother was depressed.

The main finding of the study was that the authors observed two distinct patterns of sleep over the first three years of life:

two-thirds of children, whom they called “sleepers”, were able to sleep through most nights without waking their parents after the age of six months
while about one third of children, called “transitional sleepers” took longer to achieve this, with frequent awakenings extending into the second year of life

When looking for associations, they found that “transitional sleepers” were more likely to be boys, to be breastfeeding at six and 15 months, to be seen by their mothers as having a “difficult temperament”, and to have mothers who were depressed when their baby was six months old.

The media’s claim that this research provides definitive evidence that ‘leaving babies to cry is best’ is totally unsupported by the results produced in this paper. This advice was simply a suggestion by the authors, not a result-driven conclusion of this piece of research.

This study is of interest but does not provide any answers to the ongoing debate about whether to ‘pick them up or let them cry’, despite what the headlines suggest.

Where did the story come from?

The study was carried out by researchers from a number of US universities and research institutes and was funded by the National Institute for Child Health and Human Development. The study was published in the peer-reviewed journal, Developmental Psychology.

The reporting on this study by both the Daily Mail and The Daily Telegraph is very poor and is almost certainly based on an accompanying press release, rather than the study itself.

The advice that parents should ignore their babies crying at night, in order to encourage them to ‘self-soothe’, cannot be supported by the evidence presented in this study.

The issue of self-soothing, and the influence that other factors may have upon it (such as breastfeeding and maternal sensitivity), is mentioned at several points in the research paper, where the researchers discuss the findings of previous studies.

However, they present no fresh evidence about whether self-soothing ‘works’ or not, or is ‘best for a good night’s sleep’.

What kind of research was this?

This was an observational study that looked at the sleeping patterns of over a thousand babies when they were aged 6, 15, 24 and 36 months.

It then explored whether sleeping patterns were associated with many other factors, including:

child temperament
breastfeeding
security of attachment (how secure the child feels when their parent is nearby)
illness
maternal depression
maternal “sensitivity”

Researchers also examined individual differences in sleep awakening at different points in infancy, and whether the identified factors associated with these varied at different times.

Getting babies to sleep through the night or to put themselves back to sleep once they have woken, is a common parental concern, as the authors rightly point out. Continual night-time wakening can disrupt the emotional life and schedules of families. Waking up at night is normal in infancy the authors say, but generally babies learn to soothe themselves and return to sleep without ’signalling’ to their parents by crying or calling out. However, as many as half of all children have been reported to have problems with night-time waking at some time in their first four years of life.

The underlying causes are not well understood, but sleep difficulties in babies have previously been associated with the factors listed above, as well as others such as gender, maternal sensitivity, presence of a father, childcare and birth order.

What did the research involve?

The researchers recruited an initial 1,364 new mothers to their study from hospitals across the US. They visited the mothers and children at home when the children were aged 1, 6, 15, 24 and 36 months old and made telephone contact at intervening three-month intervals.

At each visit, the mothers completed questionnaires about themselves, the child and their family, and also took part in interviews.

Children and their mothers visited the university laboratories when the children were 15, 24 and 36 months old, where researchers assessed the children and observed mothers and children playing together.

Assessment of sleep patterns:

When the children were 6, 15, 24 and 36 months, the mothers were asked about their child’s night-time sleep in the previous week, including whether the child had woken them, how many nights, how many times during the night, how long the child was awake and how much of a problem this caused for them and their families.
At 24 and 36 months, mothers completed a widely used screening checklist on their child’s sleep behaviour.

Assessment of other factors and family characteristics:

At one month, mothers reported their child’s gender and ethnicity, birthweight and birth order in the family.
At six months, mothers completed a standardised questionnaire to measure the child’s temperament.
At 6 and 15 months, mothers reported whether their infants were breastfeeding.
At 15 months, infants and mothers were videotaped in the “Strange Situation”, a technique used to assess the infants’ attachment to its mother. This works by assessing how an infant reacts to its mother when they are both placed in an unfamiliar environment – the idea being that infants who automatically turn to their mother for support have greater levels of attachment.
At 6, 15, 24 and 36 months, mothers reported any common health problems in the preceding three months, they also completed a standard questionnaire used to diagnose depression.
At 15 months, mother-child interactions were videotaped to assess maternal “sensitivity”.
Researchers also assessed the quality of parenting and the home environment, maternal health, the presence of the father or a partner in the home, family size, father’s or partner’s health, income, mother’s education, childcare and marital conflict.

The researchers used complex modelling techniques to analyse the infant/child’s sleep patterns, including looking at how this changed over time in the individual, and to look for associations between sleep patterns and the various other factors and family characteristics they had examined.

What were the basic results?

The study was completed by 1,215 mothers (of the 1,364 originally recruited). The researchers identified two distinct developmental patterns of sleep in the children:

66% of children showed a ‘flat trajectory’ of sleep awakenings from 6 through 36 months, with mothers reporting their infant waking from sleep about one night per week. The researchers called this group ‘sleepers’.
34% of the infants had seven reported nights of awakenings per week at six months, dropping to two nights per week at 15 months and to one night per week by 24 months. They called this group ‘transitional sleepers’.
When looking for associations, they found that this second group were more likely to be boys, score higher on the six-month difficult temperament assessment, to be breastfed at 6 and 15 months old, and to have a higher rate of depressed mothers at six months old.
For infants in both groups, reported sleep awakenings were associated with difficult temperament, breastfeeding, infant illness, maternal depression, and greater maternal sensitivity.
Infant-mother attachment measures were not related to sleep awakenings.
At 36 months, about 6% of children were still waking every night.

How did the researchers interpret the results?

The researchers say that generally, signalling upon waking at night (such as calling or crying) has a ‘clear developmental course’ over the first three years of life and that by six months most children are waking their parents no more than one or two nights a week. However, they say parents and health professionals should be aware that some generally healthy infants might still be waking in their sleep in their second year of life. Genetic factors – reflected in measurements of a child’s temperament – may be implicated in early sleep problems, they say, as well as breastfeeding experiences, childhood illnesses, maternal depression and sensitivity.

Parents might be encouraged to help babies with ‘self soothing’, and to seek occasional respite, they say. Families who report sleep awakenings in infants older than 18 months may need further help.

Conclusion

This was a complex modelling study, although its main message seems obvious: some babies take longer to settle into ‘sleeping through’ than others. When looking to see whether various other factors were associated with sleep difficulties they found associations including childhood illness, breastfeeding (because babies get used to falling asleep on the nipple), difficult temperament and maternal depression.

However, from this it is not possible to imply cause and effect. For example, the baby having a difficult temperament or the mother having symptoms of depression could well be the result of lack of sleep, rather than the cause of it.

Whether leaving a baby to cry itself to sleep will help them sleep through is uncertain and not explored in this paper.

The paper also has several other methodological limitations. It used a computer modelling technique to come up with the theory that children fall into two distinct developmental patterns of sleep awakening, but this remains only a theory. The study also relied on mothers self-reporting their baby’s sleep patterns with no objective measurements used (for example, recorded observations of the infant sleeping during the night). It is possible that some mothers find their baby’s waking at night more problematic than others and their reports of sleep patterns may therefore contain an element of subjective bias. Also, as the authors note, the measures of differences between the “Sleeper” and “Transitional Sleepers” were modest in magnitude.

Waking at night is normal in new babies, but continuing night-time waking can cause difficulties for parents as well as siblings. Read more about soothing a crying baby.