Does Sleep Training Harm Babies? What a Trial of 326 Babies Found at Age Six
Price et al. · Pediatrics, 2012 · Topics: Sleep
⚠ General information only — this page explains one study and isn't medical or parenting advice for your specific child.
TL;DR: It is the question that follows sleep training around: does teaching a baby to settle cause damage that shows up later? One Australian trial is built to answer it properly. Researchers randomly assigned families of 326 babies with sleep problems to a brief behavioural sleep program in infancy, or to usual care, then waited five years and checked the children again at age six — their emotions, behaviour, stress, sleep, their closeness to their parents, even signs of attachment problems. On every single measure, the two groups were indistinguishable. No evidence of harm. But read the other half too: no lasting benefit either. By six, the early sleep gains had washed out completely.
The short answer: no harm found at five years — and no lasting benefit, either
If you came here worried, here is the honest version first. The fear about sleep training has always been a long-term fear: not that a baby cries tonight, but that something in them is quietly damaged — their stress system, their bond with you, their mental health years down the line.
So one group of researchers decided to check. Five years after the program, the children who had been sleep trained as babies looked the same as the children who hadn't — on behaviour, on stress, on sleep itself, and on how close they were to their parents. The authors' own summary is unusually plain: behavioural sleep techniques have "no marked long-lasting effects (positive or negative)."
That second half matters. This paper does not say sleep training is a gift you give your child's future. It says it is a tool with a shelf life: it helps families sleep in the short term, and five years later there is simply no trace of it — good or bad.
What did the researchers actually do?
Price, Wake, Ukoumunne and Hiscock ran the five-year follow-up of a randomized trial in Melbourne, Australia. From 692 infants recruited through well-child centres, they took the 326 whose parents reported a sleep problem at 7 months old, and randomly allocated their families: 173 to the sleep program, the rest to usual care.
The program itself was brief. When the babies were 8 to 10 months old, nurses taught the parents behavioural sleep techniques over one to three individual consultations. Then everyone went home, and life happened.
Five years later, when the children were six, 225 families — 69% of the original group — came back to be measured. The researchers were blinded to which family had been in which group. And the list of what they checked is really the point of this paper: child mental health (emotional and behaviour scores), sleep problems and sleep habits, psychosocial functioning reported by both parents and the children themselves, stress regulation, the child–parent relationship — closeness, conflict, the relationship overall, and a measure of disinhibited attachment — plus the parents' own depression, anxiety, stress and parenting style.
Does sleep training damage babies? What the age-six check found
Nothing showed up. On the outcomes parents worry about most, the sleep-trained children and the control children were statistically indistinguishable at six.
Emotional scores: no difference. Behaviour (conduct) scores: no difference. How the children were functioning day to day, by their parents' report and by their own: no difference. Stress is the one critics point to most, so it is worth being specific: the share of children flagged as chronically stressed was 29% in the trained group and 22% in the control group — a gap in the "wrong" direction that was well within what chance produces at this sample size, and not a significant difference.
The wording matters here: the paper reports no evidence of differences. That is not the same sentence as "proof nothing happened," and the limits section below is honest about the gaps. But this is what a harm, if one existed at any meaningful size, would have had to hide behind — a randomized comparison, measured five years out, across this many outcomes.
Does sleep training affect babies beyond sleep? Stress, behaviour and the parent–child bond
Beneath the sleep argument sits a different worry: if a baby cries and nobody comes, does something between parent and child break?
This trial measured that as directly as questionnaires allow. At age six, the two groups did not differ on parent–child closeness, on conflict, on parents' overall rating of the relationship, or on disinhibited attachment — the pattern of overly indiscriminate friendliness that can signal attachment difficulties. The parents themselves looked the same too: depression, anxiety and stress scores matched, and the share parenting in an authoritative style was 63% in the trained group and 59% in the control group.
One honest qualification, and the paper's design forces it: all of this was measured with questionnaires and rating scales filled in by parents and children. Nobody watched these families interact in a laboratory, and there was no observational attachment test. Questionnaires are how most of developmental research works, and a broken bond would be expected to leave fingerprints on them — parents in a damaged relationship do not usually rate it as close. But "no signal on the measures used" is the accurate claim, and it is the claim this article is making.
The other half of the result: no lasting benefit either
You hear less about the other half from the people selling sleep training. At age six, sleep problems were reported for 9% of the trained group and 7% of the control group — again, no significant difference. The sleep habits scores matched too.
So what happened to the head start? It faded, the way early advantages in this trial were always going to. The earlier trials behind this one — cited in this paper's own background — showed the techniques genuinely work in the short to medium term: babies settle faster, parents sleep, maternal depression lifts. That relief is real, and for an exhausted family it can be reason enough. But it is relief for that season, not an investment in the six-year-old. By six, the children whose parents never got the program had caught up on their own.
What this study can't tell you
It tested one brief, supported program — not everything sold as sleep training. Nurses, one to three consultations, standard behavioural techniques, babies 8 to 10 months old whose parents had reported a sleep problem. This paper cannot bless or condemn a specific book, app, coach or named method, and it says nothing about leaving a baby to cry unattended for long stretches — that was never what was trialled.
It ends at age six. Whatever the teenage years hold, this study cannot see it.
Nearly a third of the families didn't come back. 225 of 326 took part at follow-up. The researchers found no differences among those who did — but missing families are a real limit, and one reason the paper's own claim is "no marked effects," not "no effects of any size, ever."
The parents knew which group they were in. The researchers measuring outcomes were blinded; the parents filling in the questionnaires were not. Most of these outcomes are parent-reported, so expectations could shade the answers — in either direction.
One city, one kind of family. Melbourne, recruited through well-child centres, and every baby started with a reported sleep problem. Families whose babies slept fine were never in this trial.
If you're weighing it up: how to read this result
Everything below is the practical part, not findings — how this one paper's result can fairly be used while you decide. What the trial actually supports is narrower and, for most exhausted parents, more useful than either side's slogans:
- Deciding not to sleep train costs your child nothing measurable here. The control families' children were indistinguishable at six on every outcome. "If I don't do this, am I failing them?" has an evidence-based answer, and it is no.
- Doing it is not a long-term investment either. If you use behavioural techniques, use them for the reason the evidence supports: your family needs sleep now. Anyone selling them as protection for your child's future mental health is selling past this paper.
- Stay inside what was actually studied. What got tested was a brief, supported set of techniques taught by a nurse, for a baby with a real sleep problem, in the second half of the first year. The closer your situation is to that, the more this result is about you. The further away it drifts — younger babies, unsupported marathon crying, methods nobody trialled — the less this paper can say.
- Stopping is allowed. Because there is no lasting effect in either direction, there is no sunk cost to protect. If you start and it doesn't fit your baby or your family, the children in this study who never did it at all turned out fine — stopping leaves no mark the researchers could find either.
Frequently Asked Questions
Is sleep training bad for babies?
On the longest and best evidence available, no — not in any way researchers could measure five years later. The trial behind this article randomly assigned families to a behavioural sleep program in infancy and found the children indistinguishable at six on emotions, behaviour, stress, sleep and the parent–child relationship. That is not the same as a guarantee: the study rules out marked long-term harm from one brief, nurse-taught program, and it cannot speak for every method, every baby, or the years past six.
Is sleep training safe for babies?
'Safe' covers a lot of ground, and no single study settles a word that big. But the specific fear — lasting damage to a child's mental health, stress system or attachment — is the one this trial was designed to catch, and it found no sign of it at age six. The fair summary is the authors' own: no marked long-lasting effects, positive or negative. What the study does not cover is the short term, other methods, or babies without sleep problems; for your own child's situation, their clinician knows the parts a study can't.
Does sleep training negatively affect babies' attachment?
It is the worry underneath most of the others, and this trial did measure it — by questionnaire, not in a laboratory. At six, the trained and untrained groups did not differ on disinhibited attachment, on parent–child closeness, or on conflict. So there is no signal here that a brief behavioural program damaged the bond. Be precise about the boundary, though: attachment was rated on scales, not observed, and the program tested was short and supported. "No signal on the measures used" is what the evidence says — and on the fear as most parents mean it, that is genuinely reassuring.
If it does no harm, should every family sleep train?
The same paper that clears sleep training of harm also removes the pressure to do it. There was no lasting benefit: by six, sleep problems were just as common in the trained group as in the control group (9% vs 7%). So this is not a developmental duty in either direction. It is a tool for a hard stretch of family life — worth using if your household needs sleep now, and entirely skippable if it doesn't.
📄 The paper at a glance
Price, A. M. H., Wake, M., Ukoumunne, O. C., & Hiscock, H. (2012). "Five-Year Follow-up of Harms and Benefits of Behavioral Infant Sleep Intervention: Randomized Trial." Pediatrics, 130(4), 643–651. DOI: 10.1542/peds.2011-3467
- Design: 5-year follow-up of a population-based cluster-randomized trial — families allocated by chance, outcomes measured at age 6
- Who: 326 babies in the original trial (173 in the program), all with parent-reported sleep problems at 7 months, Melbourne, Australia; 225 families (69%) measured at follow-up
- The program: behavioural sleep techniques taught by nurses over 1–3 consultations, at infant age 8–10 months, vs usual care
- Headline result: no evidence of differences at age 6 on any outcome — emotional and behaviour scores, sleep problems (9% vs 7%), chronic stress (29% vs 22%), parent–child closeness and conflict, disinhibited attachment, or parents' depression, anxiety and stress
- What it doesn't show: a verdict on any specific named method, effects past age six, proof of zero effect at any size, or a lasting benefit — none of those are in this paper either
The takeaway
Parents arguing about sleep training usually argue as if the stakes were permanent — damage on one side, duty on the other. The best long-term evidence says the stakes are smaller and kinder than that. A brief behavioural program in infancy left no mark a research team could find at age six: not on behaviour, not on stress, not on the bond between parent and child — and not on sleep itself, which had equalised anyway. Which frees the decision to be what it probably always should have been: not a verdict on your parenting, just a question about what your family needs this season.
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Disclaimer: This article explains scientific research and is not medical or parenting advice for a specific child.