Pregnancy and child

Controlled crying 'safe for babies'

"Leave your baby to cry," The Daily Telegraph today advised, along with the Daily Mail. Both were commenting on the "best" way to get an infant into a sleep routine. Unfortunately for exhausted new parents, it's not always that simple.

This news is based on research looking at the long-term effects of two controversial ways of improving infant sleep patterns, known as "controlled crying" and "camping out".

Both techniques have been proven to be effective in improving sleep habits. But critics have argued that leaving a baby to cry exposes them to unnecessary stress and trauma that could cause both psychological and physical problems in later life.

Researchers looked at whether children who went through these types of parenting experienced any long-term harms when compared with children who didn’t. The study found that these behavioural sleep techniques had no significant harmful or beneficial effects on these sort of issues.

Employing these techniques with your own child is entirely a matter of personal preference. This study appeared to find that doing so will neither harm nor help your child in the long-term. However, it is worth noting that the study did not include infants younger than seven months old. Therefore these findings can’t be generalised to younger babies.

Read more about Getting your baby to sleep.

Where did the story come from?

The study was carried out by researchers from the University of Melbourne, Australia and the University of Exeter, UK. It was funded by the Australian National Health and Medical Research Council (NHMRC), the Pratt Foundation, the Financial Markets Foundation for Children and the Victorian Government (for the state of Victoria) in Australia. 

The study was published in the peer-reviewed medical journal, Pediatrics.

The researchers noted that behavioural techniques are known to effectively reduce infant sleep problems and associated maternal depression in the short- to medium-term. However, the long–term effects of such interventions are not known, but often debated. The researchers set out to determine any potential harm on children’s emotional development, their mental health and ability to deal with stress as well as the child-parent relationship.

The main body of the story was covered appropriately by the Daily Telegraph but the headline “Leave your baby to cry, scientists say” is misleading. The researchers, perhaps wisely, made no recommendation on whether parents should employ these types of techniques.

The Daily Mail’s headline incorrectly reports that letting babies cry is the “secret to longer sleep”, which is not the case. While the original study of eight-month-old babies found that parents receiving the intervention reported 40% fewer sleep problems in their infants at 10 months, this follow-up study did not look at length of sleep.

What kind of research was this?

This was a five-year follow-up of a cluster randomised controlled trial (RCT) looking at the long-term harms or benefits of a behavioural sleep programme for infants at the age of six years old.

An RCT is the best type of study design to determine whether a treatment is effective as it compares the effects of an intervention with another intervention or a control (such as a placebo). In cluster RCTs, participants are randomised in groups rather than as individuals. Examples of clusters that could be used include schools, neighbourhoods or GP surgeries. For this particular study, child health nurse centres were used. 

What did the research involve?

The study was called the “Kids Sleep Study”, which in turn was a five-year follow-up of a previous study, called the “Infants Sleep Study”.

In the original study, researchers recruited 328 infants with sleep problems identified by their parent or parents at the age of seven months. These infants were recruited from 49 maternal and health child nurse centres across six diverse local government areas in Australia.

Researchers then randomised the 49 health centres (cluster randomised) to either a centre that delivered the behavioural intervention or to usual care (such as general advice from a nurse).

For the centres randomised to deliver the intervention, trained nurses delivered a brief standardised behavioural sleep intervention (including "controlled crying" and "camping out") over three sessions beginning at the routine eight-month "well-child check". Each family was able to choose the type and mix of strategies they preferred to try to manage their infant’s sleep. Families receiving usual care who were allocated to control health centres were able to attend the scheduled eight-month well-check and ask for sleep advice but nurses at these centres were not trained to deliver specific sleep-management techniques.

The researchers then re-contacted the families when the children were approximately six years old, and of the 326 that were eligible for further analysis, carried out tests to look at the child’s:

  • mental health
  • sleeping pattern
  • psychosocial functioning
  • relationship with the parents
  • mother’s mental health (depression, anxiety and stress)
  • parents’ parenting styles
  • levels of stress

Stress levels were measured by asking the parents to take a sample of salivia from each child (using a test tube which was then mailed back to the researchers). The researchers then measured cortisol levels in the sample (cortisol is a hormone than is released during moments of stress).

The statistical analysis was appropriate in this study and when analysing results the researchers adjusted the results for various confounders such as:

  • child gender
  • child temperament
  • maternal depression
  • socioeconomic status including maternal education

What were the basic results?

At the five-year follow-up, 225 children and their families were included from the 326 that were eligible (69%). The key finding of this study was that there were no differences seen between children and their mothers who received a behavioural intervention compared with those who received usual care for any of the outcomes studied. This was found for both unadjusted and adjusted data. 

How did the researchers interpret the results?

The researchers concluded that behavioural sleep techniques do not cause long-lasting harms or benefits to the child, their relationship with their parents or their mother’s health. Parents and health professionals can confidently use these techniques to reduce the short- to medium-term burden of infant sleep problems and maternal depression.

Lead researcher Dr Anna Price said: "For parents who are looking for help, techniques like controlled comforting and camping out do work and are safe to use."


Overall, the results from this well-conducted trial provides some evidence to suggest that along with important short-term benefits to the mother and baby, there may be no harmful (or benefical) effects to the child and mother five years after the introduction of behavioural interventions.

The study has some limitations, some of which are noted by the authors:

  • The research only involved babies who were at least seven months old with reported sleeping problems. Sleeping problems as identified by parents will vary and it is not possible to generalise these findings to infants younger than seven months.
  • There was a relatively high number of children and their families that were not followed up from the original sample (31%) as they did not respond to further questionnaires or provide a salivia sample.
  • This relatively high “drop-out” rate may bias the results, particularly as there were more non-English speaking and disadvantaged families that were not followed-up.
  • Despite the researchers being “blinded” to which group children were allocated to when they did their analysis, the parents of the children were not “blinded”, and may have responded more or less favourably at the five-year follow-up, knowing which group they were in. This could also have influenced the results.

The researchers mentioned that it is unknown whether there are subgroups of infants, such as those who have previously been maltreated or who have experienced early trauma, for whom the techniques may be unsuitable in the short or long-term.

Finally, as Dr Price also noted, parents should not misinterpret the findings to mean letting infants cry throughout the night. 

Analysis by *NHS Choices

. Follow Behind the Headlines on twitter*.

NHS Attribution