Little Dream Zone

For worried parents

Thinking about sleep training? Here's what the research actually says

It's completely normal to feel anxious about it. Most worries come down to one question: "Will it harm my baby or our bond?" Here is a plain-English summary of the main studies, including what they don't tell us, with links so you can read them yourself.

The research at a glance

52

studies reviewed; 94% found behavioural sleep approaches helped

Mindell et al., 2006 [1]

5 yrs

later: no differences in behaviour or closeness to parents

Price et al., 2012 [2]

178

babies followed to 18 months: attachment just as secure

Bilgin & Wolke, 2020 [3]

2,090

families: longer night sleep, no difference in parent–baby bonding

Kahn et al., 2023 [4]

The key studies, in plain English

Each card shows what researchers did, what they found, and what to keep in mind. No single study is perfect, so it's the overall pattern that matters.

The big review

Mindell et al., 2006 · Sleep · American Academy of Sleep Medicine task force

What they did
Reviewed 52 studies of behavioural sleep approaches for babies and young children.
What they found
94% of studies found the approaches worked. Over 80% of children improved, and the improvement lasted at least 3–6 months. No harmful side effects were reported.
Keep in mind
Only a few of the studies measured emotional side effects, so this review tells us more about whether it works than about long-term wellbeing.
Read the study [1] →

Five years later

Price et al., 2012 · Pediatrics · randomised controlled trial, Australia

What they did
326 babies with sleep problems at 7 months were split into two groups at random. One group's parents learned "controlled comforting" (timed check-ins) or "camping out" (gradually moving a chair out of the room). The children were checked again at age 6.
What they found
No differences in emotional or behavioural problems, closeness or conflict with parents, or parents' stress between the two groups.
Keep in mind
There was no lasting harm, but no lasting extra benefit by age 6 either. The gains were in the short to medium term.
Read the study [2] →

Attachment at 18 months

Bilgin & Wolke, 2020 · Journal of Child Psychology and Psychiatry · University of Warwick, UK

What they did
Followed 178 UK babies from birth to 18 months. Mothers reported how often they left their baby to cry in the first 6 months. At 18 months, researchers observed each baby's attachment and development.
What they found
Babies who were sometimes or often left to cry were just as securely attached and developed just as well. They also fussed and cried for shorter periods at 18 months.
Keep in mind
This was about everyday crying, not a sleep training programme. How often babies were left to cry came from mothers' own reports, and it can't prove cause and effect. Some researchers think its conclusions are too strong [6].
Read the study [3] →

Real families, real homes

Kahn, Barnett & Gradisar, 2023 · The Journal of Pediatrics · USA

What they did
Surveyed 2,090 parents of babies aged 3–18 months. Video sleep tracking from their baby monitors showed how the babies actually slept.
What they found
Check-in style and cry-it-out methods were harder for parents but worked faster, and babies slept longer at night. Staying in the room was easier but slower. There was no difference in parent–baby bonding or parents' mood between methods.
Keep in mind
Families chose their own method, so it can't prove cause and effect. Most were well-educated US families, and the study was funded by Nanit, the baby monitor company. Many parents started before 6 months, earlier than recommended.
Read the study [4] →

A review of the reviews

Drozd et al., 2022 · Acta Paediatrica · Norway

What they did
Brought together 5 systematic reviews covering 24 studies (mostly randomised trials) and several thousand families with babies up to 1 year old.
What they found
Behavioural approaches increased babies' night sleep, and parents' sleep too. Key ingredients were good bedtime routines, understanding baby sleep, and helping babies settle on their own. Briefly not responding straight away at sleep times did not seem to affect attachment.
Keep in mind
Benefits for night wakings and mothers' mood were less certain, and results varied between studies. The authors recommend adapting the approach to each family.
Read the study [5] →

Sleep training isn't one thing

"Sleep training" covers many methods, from very gentle to very structured. Most of the research is on the faster methods on the right, and it hasn't found harm even there.

More gradual · usually less crying · slower Faster · more crying at first

Parental presence

You stay in the room, offering comfort, and gradually do less.

Gradual retreat ("chair method")

You sit by the cot and move a little further away every few nights.

Check-ins / pop-ins

You leave, then return at set intervals for brief reassurance.

Extinction ("cry it out")

You say goodnight and don't return until morning.

The trade-off: in the largest real-world study [4], the faster methods worked sooner but felt harder for parents. Staying in the room felt easier but took longer. Neither made a difference to bonding. The right choice is the one your family can stick with.

The honest bits

What the research does not say

  • It doesn't say every baby must be sleep trained. Many families are happy as they are, and that's fine.
  • It doesn't support sleep training under about 6 months. Young babies need night feeds and close responsive care [7].
  • It isn't a cure-all: results vary, and the benefits for night wakings and mums' mood are less certain than for overall sleep [5].
  • Researchers don't all agree, and studies have limits, such as small samples and relying on parents' own reports [6].

Good signs you're ready

  • Your baby is around 6 months or older, healthy and growing well.
  • Your GP or health visitor has checked out any medical concerns, such as reflux, allergies or snoring.
  • The sleep space follows safe sleep advice.
  • All the adults involved agree and can be consistent for about 2 weeks.
  • There are no big changes coming up, such as a holiday, a house move or starting nursery.
  • You feel it's right for your family. You can pause or stop at any time.

Remember

You're still respondingGentle methods involve checking on, comforting and reassuring your child throughout.
Some protest is normalCrying when something changes is communication, not harm. It usually eases within days.
You're in chargeEvery plan is built around your child, your values and what you're comfortable with.
Rested parents help tooBetter sleep for the whole family is a valid reason to want change.

Sources

  1. Mindell JA, Kuhn B, Lewin DS, Meltzer LJ, Sadeh A. Behavioral treatment of bedtime problems and night wakings in infants and young children. Sleep. 2006;29(10):1263–1276. aasm.org (full text)
  2. Price AMH, Wake M, Ukoumunne OC, Hiscock H. Five-year follow-up of harms and benefits of behavioral infant sleep intervention: randomized trial. Pediatrics. 2012;130(4):643–651. publications.aap.org · doi:10.1542/peds.2011-3467
  3. Bilgin A, Wolke D. Parental use of 'cry it out' in infants: no adverse effects on attachment and behavioural development at 18 months. J Child Psychol Psychiatry. 2020;61(11):1184–1193. doi.org/10.1111/jcpp.13223
  4. Kahn M, Barnett N, Gradisar M. Implementation of behavioral interventions for infant sleep problems in real-world settings. J Pediatr. 2023;255:137–146. doi.org/10.1016/j.jpeds.2022.10.038
  5. Drozd F, Leksbø TS, Størksen HT, Wilhelmsen CEW, Slinning K. An overview of reviews for preventing and treating sleep problems in infants. Acta Paediatr. 2022;111:2071–2076. doi.org/10.1111/apa.16475
  6. Davis AM, Kramer RS. Commentary: Does 'cry it out' really have no adverse effects on attachment? Reflections on Bilgin and Wolke (2020). J Child Psychol Psychiatry. 2021. repository.lincoln.ac.uk
  7. NCT. Is it OK to let my baby cry? (citing Basis, the Baby Sleep Info Source). nct.org.uk

This summary is for general information and is not medical advice. If you're worried about your child's health, growth or breathing, speak to your GP or health visitor first. Summary prepared by Little Dream Zone, October 2026.