Read When: People are Claiming Sleep Training is Safe or Effective

There isn’t a lot of science that looks directly at the safety or effectiveness of sleep training. Safety in particular is difficult to study directly, due to ethical standards. You can’t randomise babies into a group where the outcome might put them at risk of physical or psychological harm. It’s also hard to study effectiveness because developmental trauma and attachment disorders often don’t show up until adulthood. But here’s what we can do.

What Does The Research Say?

We critically deconstruct the research into early trauma


We can look at existing research that claims sleep training is safe, effective (baby sleeps more/parent sleeps more) and helps with mood (parents/prevents later mental health issues) and critically assess them. This is what journalists should be doing before they write that article titled “New Study Proves Leaving Your Baby to Cry Causes No Harm” or “Sharing a Room With Your Baby Predisposes Them to Later Mental Health Issues - Study Says”. Unfortunately, that doesn’t tend to happen. If journalists were actually reading the research, there would be no articles with those claims, because the research usually proves no such thing.

So what does the research say? The following articles critically deconstruct the research.

Behavioural Sleep Interventions in the First Six Months of Life Do Not Improve Outcomes For Mothers or Infants Dr Pamela Dougals, Dr Peter Hill - Journal of Developmental and Behavioural Paediatrics
Babies and Sleep A Matter of Choice Dr Pamela Douglas - The Possums Clinic


Dr Tracy Cassels of Evolutionary Parenting spends a large amount of her time deconstructing parenting research. It’s her speciality. The following articles are all hers.

Mythbusting Sleep Training Claims - Science Style
Distress Self Soothing and Extinction Sleep Training
Should babies sleep alone? An Analysis of the INSIGHT Study’s Findings on Infant Sleep by Location Helping Baby Sleep: Does Extinction Sleep Training Improve Baby’s Sleep?
How Effective is Controlled Crying?
Responsive Settling: Is it Responsive? Effective?
Stress And Extinction Sleep Training: It’s Not So Simple
Stress and Synchrony: Implications for Sleep Training
Does Bedsharing Really Cause Sleep Problems?
Controlled Crying, Cortisol and Attachment: A Critical Look
How Successful are Behavioural Sleep Interventions?
Proving the Risk of Harm in Early Sleep Training

The Following is a list of research articles that have been used in various media sources to claim that sleep training is effective, safe or helps maternal well being. None of them claim that at all.

Preventing Early Infant Sleep and Crying Problems and Postnatal Depression: A Randomized Trial

Effect of behavioural-educational intervention on sleep for primiparous women and their infants in early postpartum: multisite randomised controlled trial:

Do psychosocial sleep interventions improve infant sleep or maternal mood in the postnatal period? 

A systematic review and meta-analysis of randomised controlled trials

Postnatal parental education for optimising infant general health and parent-infant relationships.

Sleep, mood, and development in infants

Outcomes at six years of age for children with infant sleep problems: longitudinal community-based study.


There is however plenty of science that looks at the impact of stress, trauma, attachment breaks, Adverse Childhood Experiences and the like on mental health. And that research tells us quite clearly that it is always a bad idea to purposefully put a baby or child through a stressful situation. We have no idea what other risk factor situations that child will encounter in their life, our aim as parents, educators and health professionals is to do whatever we can to limit acute stress, and develop resilience (both skills and factors)

It’s Just a Little Cortisol Dr Tracy Cassels - Evolutionary Parenting
Acute Stress Affects Cognition in Infancy Dr Tracy Cassels - Evolutionary Parenting
The Thing About Trauma Dr Tracy Cassels - Evolutionary Parenting
No Stress in Sleep Training - A Response Dr Tracy Cassels - Evolutionary Parenting
The Myth Of Warmth Dr Tracy Cassels - Evolutionary Parenting


At the end of the day we can’t say for sure that sleep training of any kind is safe, because we don’t know what any individual child’s life is going to be like. We don’t know how many stressful events they will encounter. We don’t know how much resilience they will be able to build. We’re playing russian roulette.

What Children Don’t Need Can Still Help Them Dr Tracy Cassels - Evolutionary Parenting

Dangers of “Crying It Out” Darcia Nrvaez PHD Psychology Today

Cry It Out - 6 Educated Professionals Who Advise Against It Kelly Wilder - Belly Belly

Position Paper - Australian Association For Infant Mental Health

Shifting Priorities: Why Sleep isn’t the most Important Thing For Your Child Dr Tracy Cassels - Evolutionary Parenting

Sleep Learning and The Zone of Proximal Development Nicole Gorring - Integrity Calling

Fussy Babies and Later Mental Health Problems Dr Tracy Cassels - Evolutionary Parenting