Sleep Training Your Baby: What Does the Research Say?

Sleep training is one of the most debated topics in parenting. Some swear by it. Others think it's harmful. Most are simply uncertain.

Here you'll get an overview of what sleep training is, which methods exist, and what research and health authorities say.

What Is Sleep Training?

Sleep training is an umbrella term for methods in which a baby gradually practices falling asleep — and falling back asleep after waking — with less help from parents.

The goal is not to teach the baby that they are alone. The goal is to help them self-settle without depending on one specific external factor, such as nursing or rocking, to fall asleep.

Sleep training is not the same as letting a baby "cry it out" uncontrolled. Most methods are far more nuanced than that.

How Common Are Sleep Problems?

Around 25 percent of all children between 0 and 5 years have sleep problems, according to public health research. This includes difficulties falling asleep, frequent night wakings, and daytime consequences.

For many parents, sleep deprivation is one of the toughest aspects of the first year. That's the context for why sleep training is discussed at all.

Different Methods — From Gentle to More Structured

There is no single sleep method. Here are the most common ones, from gentlest to most consistent:

Fading (Gradual Reduction)

You help the baby as usual, but gradually reduce how much help you provide. You nurse for a shorter time, or sit a little farther away before the baby falls asleep.

This method takes longer but involves minimal crying and is gentle. It works well from around 4–6 months of age.

Controlled Comforting (Graduated Extinction / Ferber Method)

You put the baby down drowsy but awake, and wait for short intervals — typically 3–5 minutes — before going in to offer brief comfort. The wait time increases gradually.

The National Sleep Medicine Center describes graduated extinction as one of the best-documented methods for sleep problems in infants and toddlers. Research published in the journal Pediatrics shows that the method improves children's sleep and mental health, and reduces depressive symptoms in mothers.

Chair Method

You sit in the room until the baby falls asleep, but don't actively comfort. The chair is gradually moved closer to the door over several weeks.

The method requires patience, but many parents find that your physical presence makes it feel safer for both of you.

Scheduled Awakenings

You wake the baby yourself — 15–60 minutes before they typically wake on their own. Gradually, these planned wakings are reduced as the spontaneous ones disappear.

Sleep medicine specialists recommend this method particularly for frequent and predictable night wakings.

CIO — "Cry It Out" (Full Extinction)

The most controversial method. The baby is put down and parents do not respond to crying until the next morning or a set time.

This approach is uncommon in clinical practice and is generally not recommended by mainstream health authorities.

What Do Health Authorities Say?

The WHO and AAP emphasize that babies do not need to learn to fall asleep without help. Responsive caregiving — responding to your baby's cues — is central to recommendations for infants.

Sleep medicine specialists distinguish between normal night waking and sleep problems that need intervention. When sleep difficulties are persistent and affect the whole family, graduated withdrawal is described as effective and well-documented.

Medical resources note that for established sleep problems from around 6 months of age, graduated extinction is the best-documented treatment. They recommend personalized guidance from a pediatrician or child health nurse.

What Does Research Say About Safety?

The research is more nuanced than the debate often suggests.

Effectiveness

94 percent of studies on behavioral sleep interventions show that the methods are effective. Children sleep longer, wake less often, and parents get more sleep. This is well-documented in the research.

Cortisol and Stress Levels

A 2012 study (Middlemiss et al.) found that infants' cortisol levels remained elevated on day 3 of CIO training, even after crying had stopped. It found that mother and baby's stress responses became "unsynchronized" — the mother calmed down, but the baby did not.

Another large study, published in Pediatrics (Price et al., 2012), showed that graduated extinction did not produce elevated cortisol levels in infants, and that there were no negative effects on attachment or emotional development at the 12-month follow-up.

The cortisol picture is therefore not straightforward — it depends on the method and how it is carried out.

Attachment

The concern many parents have is whether sleep training damages the emotional bond with their child.

Long-term studies show no negative effect on attachment when graduated extinction is carried out from 6 months or older. It is important to note that context and sensitivity matter — sleep training carried out by secure, loving parents with a good relationship with the child is not the same as persistent ignoring of needs.

Breastfeeding

Sleep training, especially methods involving significant crying, can reduce milk supply because night nursing contributes substantially to milk production. This is an important factor for breastfeeding mothers to consider.

Cultural Perspective: Responsive Caregiving

In many Western parenting traditions, responsive caregiving is emphasized — the idea that babies need adults to respond to their signals in order to build secure attachment and basic trust.

The AAP and WHO both support this perspective. It doesn't mean babies should never practice falling asleep independently, but that it should happen gradually, in an age-appropriate way, and within a safe, supportive relationship.

Hundreds of child psychologists have signed letters against sleep books they felt promoted methods in conflict with what they described as the child's fundamental need for safety and co-regulation. This illustrates that a more cautious approach exists alongside the mainstream Anglo-American perspective.

When Might Sleep Training Be Worth Considering?

Sleep training is not necessary for all children — and for many, it's not relevant at all. But it may be worth considering when:

• The baby is over 4–6 months and has established a clear day-night rhythm
• Sleep deprivation is affecting the family's health and wellbeing over time
• Other measures — routines, wake windows, bedtime rituals — haven't helped
• The baby is healthy and not in the middle of a developmental leap or regression
• Both parents are comfortable with the approach

Alternatives to Formal Sleep Training

Many parents find good results with approaches that are not considered traditional sleep training:

• Consistent bedtime routines — Bath, feed, book, goodnight. Consistency creates predictability.
• Appropriate wake windows — An overtired baby paradoxically sleeps worse. Read our guide to wake windows.
• Sleep environment — Dark room, room temperature 18–20°C, white noise.
• Gradual practice — Put the baby down drowsy but awake for short periods without going all the way to CIO.
• Dream feed — Feed around 10–11pm before you go to bed, to extend the nighttime stretch.
• Log sleep — The Sleep Tracker on Babysential helps you spot patterns and adjust routines based on data.

Use Your Pediatrician — They're There to Help

Your child health nurse or pediatrician is the best resource for individualized sleep guidance. They know your child, can assess the whole picture, and can tailor advice to your family's situation.

You don't have to figure this out alone. And you don't need to pay for a sleep course to get help.

Frequently Asked Questions

From what age can you start sleep training?

Most experts and health authorities do not recommend sleep training before 4–6 months. Before this, frequent wakings are biologically normal and necessary. Many professionals prefer to wait until 6 months.

Is sleep training safe?

Research on graduated withdrawal (the Ferber method and similar approaches) shows no long-term harm to attachment, emotional development, or behavior when carried out correctly from 6 months. There is more uncertainty around CIO (full extinction), and that method is rarely used in clinical practice.

Will sleep training affect breastfeeding?

It can. Night nursing contributes to milk production, and methods that reduce night feeds can reduce milk supply. Talk to your child health nurse or a breastfeeding counselor before starting, if you are breastfeeding.

What is the difference between graduated extinction and "cry it out"?

Graduated extinction means you go in and briefly comfort the child, with gradually increasing wait times. Cry it out (full extinction) means you don't respond to crying at all. These are two very different methods with different evidence bases and different stress levels for both child and parent.

Can sleep training help with sleep regressions?

Sleep regressions around 4, 8, and 12 months are temporary and biologically driven. They pass on their own. Sleep training during a regression is not recommended — wait until it's over. Read more about the 4-month sleep regression.

Can we use a sleep tracker to see if it's helping?

Yes. Logging sleep with Sleep Tracker gives you objective data on improvement over time, which is far more reliable than memory at 3am.

Summary

Sleep training is not black and white. It is also not necessary for everyone.

Graduated withdrawal from 6 months is well-documented, effective, and — according to long-term studies — not harmful to attachment. Full CIO is more controversial and rarely used in clinical practice.

What health authorities agree on: babies need responsive care, predictable routines, and present parents. Sleep improves for the vast majority — with or without formal sleep training.

Try Sleep Tracker to log and analyze your baby's sleep, or read more below.

Read More

• Checklist: Safe Sleep - Check that your baby's sleep environment is safe
• Baby Sleep Needs by Age - How much should your baby sleep?
• Wake Windows by Age: A Guide - The most important thing nobody told you
• Baby Won't Sleep at Night - 8 causes and solutions
• 4-Month Sleep Regression - What's happening and what do you do?
• Bedtime Routines for Baby - How to create good evening routines
• Sleep Tracker - Log your baby's sleep and see patterns over time

Sources

1. WHO - Infant and child sleep
2. AAP - Behavioral Sleep Interventions
3. Price et al. (2012), Pediatrics - Behavioral Interventions for Infant Sleep Problems