From time to time, yet another controlled crying study hits the headlines.

It’s a topic which always seems to set social media alight with divided opinion – from parents who sing the praises of controlled crying, and those who express deep concern about this controversial sleep training method.

So what does the latest controlled crying study have to say?

The Controlled Crying Study

The most recent controlled crying study, which was published in the journal Pediatrics, looked at a small group of families who sought help for sleep problems in their babies aged 6 to 16 months of age.

To resolve the problems, the babies were randomly assigned to one of three groups:

Graduated extinction: better known as controlled crying, and sometimes referred to as controlled comforting;
Bedtime fading: where bedtime is delayed to coincide with drowsiness;
Parent education about normal infant sleep: this was considered the ‘control group’.

Only 43 families were enrolled in the controlled crying study, which is a very limited sample. This meant that each group only contained only 14 or 15 babies.

Four areas of concern were measured:

Sleep onset latency (the length of time taken to fall asleep)
Number of night wakings (where parents were awakened)
Wake time after sleep onset (how long the infant was awake after previously falling asleep)
Total sleep time

The objectives of the study were to evaluate the effects of behavioural interventions on the sleep/wakefulness of infants, parent and infant stress, and later child emotional/behavioural problems, and parent-child attachment.

The study, complete with its major flaws, concluded: “Both graduated extinction and bedtime fading provide significant sleep benefits above control, yet convey no adverse stress responses or long-term effects on parent-child attachment or child emotions and behavior.”

There are two ways to look at disrupted sleep during the early years of parenting:

You can accept that babies and toddlers will wake at night and need parent support to return to sleep;
You can see night waking as a ‘sleep problem’ and seek to resolve that problem through training.

When we see reports of research like this, it is important to consider the findings against what we already know about infant sleep.

Should These Babies Be Sleeping Through The Night Yet?

The crucial factor in the recruitment of families for this controlled crying study was the ‘yes or no’ answer to a simply phrased question: ‘Does your baby have a sleep problem?’

The primary myth around infant sleep is the belief that ‘babies should be sleeping through the night at some point in the first year’.

The reality?

Research from the UK (which studied 715 babies) clearly shows that 78% of babies aged six to 12 months still regularly wake at least once in the night, with 61% having at least one milk feed during the night.

Most telling of all: one third of parents admit to lying about their baby’s sleep.

What About The Wonder Weeks?

The babies in this study were aged between 6 and 16 months. This is a critical period of sleep disruption associated with major mental developmental Leaps, popularly known as Wonder Weeks.

Within this timeframe, Leaps occur at 26 weeks, 37 weeks, 46 weeks, 55 weeks and 64 weeks. This age group sees most babies learning to crawl, sit, stand and walk – all significant stages of physical development. Research has shown that crawling alone disrupts sleep patterns for as long as three months after that milestone is achieved, which is on average, at 7 months.

Cortisol: The Stress Hormone

These researchers wanted to see if the babies in the study were stressed by the experience. Stress levels can be assessed by measuring the level of the hormone cortisol in a saliva sample.

Critically, these samples were not collected during the period of ‘sleep training’ but were taken after that time – one week, one month, three months and 12 months after the sleep training.

Not all of the babies were presented for these tests. While the results suggest no long-term stress, no night-time measurements were taken to assess if the baby was stressed during the actual process.

By contrast, other researchers measured the cortisol levels of babies AND mothers over the period of sleep training, and after the babies stopped waking their parents at night. While both showed higher levels of cortisol during the sleep training (which also used the controlled crying method), the babies’ levels remained raised, while the mothers’ returned to normal.

The parents’ stress was reduced by the baby no longer waking them: the babies’ stress remained high. While the babies no longer exhibited crying behaviours, elevated stress hormones indicated that they remained psychologically distressed.

Attachment – The Mother-Child Bond

The sustained high cortisol levels in babies after they ceased crying indicated they were not ‘settled’ as might be imagined.

Quite simply, the babies were not coping without their mother but had ceased calling for her. She, however, had relaxed because the baby was no longer crying. A relaxed mother and a stressed baby are out of sync. They have lost what is called a ‘synchronous interaction’. Synchronous interactions are fundamental to a secure mother-infant attachment.

The researchers used a recognised test for attachment called the Strange Situation. This is a procedure devised by Mary Ainsworth in the 1970s to observe attachment relationships between a caregiver and a child. It applies to children between the ages of nine and 18 months. Broadly speaking, the attachment styles are termed ‘secure’ and ‘insecure’

Only 54% of children were securely attached in the graduated extinction group, compared with 60% in the bedtime fading group, and 62% in the control group. While these figures are disturbing, what they also show is the overall lack of secure attachment in babies whose parents consider them to have a sleep problem.

Unfortunately, the researchers did not take the opportunity to include a genuine control group of families who did not describe their baby’s sleep as a problem. These results are higher than those of a recent study of 14,000 children in the United States, which found that 40 percent of children don’t develop strong emotional bonds – secure attachment – with their parents.

A review of international studies of attachment, Baby Bonds, found that infants aged below three who do not form strong bonds with their mother or father are more likely to suffer from aggression, defiance and hyperactivity when they get older. A key finding was that around 1 in 4 children avoid their parents when they are upset, because the parents ignore their needs. A further 15 percent resist their parents because they cause them distress.

The Australian Association for Infant Mental Health Inc (AAIMHI) is concerned that although controlled crying might stop infants and toddlers from crying, it might also have the effect of teaching children not to seek or expect support, despite remaining internally distressed. The Association is also concerned that the widely practised technique of controlled crying is not consistent with infants’ and toddlers’ needs for optimal emotional and psychological health, and could have unintended negative consequences.

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While lack of sleep is often cited as a trigger for postnatal depression, protecting adult mental health should not come at the cost of infant/child mental health. Longitudinal (long term) studies have not been done to assess the impact of extinction or graduated extinction methods of sleep training, as infants grow into children, adolescents and adults.

Recommended Reading: Study: 40% Of Children Lacking Secure Attachments.