Baby sleep training: Cry it out method

The cry it out method, also known as CIO or extinction sleep training, involves putting your baby to bed drowsy but awake at a set time every night and not responding to crying until the next morning. Cry it out can be stressful for parents, since it means allowing babies to cry until they fall asleep. However, research suggests it can quickly help babies learn to fall and stay asleep on their own, and it doesn't result in long-term attachment or behavioral problems.

baby laying on it's back in crib while awake
Photo credit: / LisaValder

What is the cry it out method?

"Cry it out" sleep training involves leaving babies alone in their cribs to cry for as long as it takes to fall asleep, and not responding if they cry during the night.

Every evening, you'll follow the same routine to prepare your baby for bedtime, then you'll put your baby in bed drowsy but awake. As long as your baby is well-fed and in a dry diaper when you put them to sleep, and not sick or hurt, you won't respond to their crying until it's time to get up the next morning – which often means up to 12 hours.

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This approach assumes that falling asleep on their own is a skill your baby can master if you give them the opportunity. It's similar but distinct from the Ferber method, where parents allow their baby to cry for a specified, short period of time before offering comfort.

Proponents of the CIO method say that if your child is used to having you rock or nurse them to sleep, they won't learn to fall asleep on their own. When they wake up during the night – as all children and adults do as part of their natural sleep cycle – they become alarmed and cry for you instead of being able to go back to sleep. If you respond to their cries, the thinking goes, you're training them to cry and need comfort every time they wake up.

In contrast, babies who learn to soothe themselves to sleep at bedtime use the same skill when they wake up at night or during a nap – which means better sleep for everyone.

Although crying isn't the goal of extinction sleep training, it's often an inevitable side effect as your baby adjusts to sleeping on their own. (Note: Though "extinction" sleep training sounds unpleasant, in psychology extinction means the eventual elimination of unwanted behaviors. Cry it out is formally known as unmodified extinction, and the Ferber method is called graduated extinction.)

Most research suggests that CIO sleep training is effective and doesn't cause any long-term harm for babies. However, some parents find it very stressful (or even impossible) to allow their baby to cry for extended periods of time without responding.

Other parents say the short-term pain is outweighed by the long-term advantages: A child who goes to sleep easily on their own, and parents who can count on a good night's rest.

When can we try the cry it out method?

Try the cry it out method when your baby is physically and emotionally ready to sleep through the night, usually between 4 and 6 months of age.

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By 4 to 6 months old, babies' sleep cycles are more regular and predictable, and they can usually go through the night without a feeding. That makes this age a good time to start sleep training.

That said, some babies who were born prematurely or who aren't gaining enough weight may need to wake to eat at night until they're older. If you're not sure whether your baby's ready for the cry it out method, talk to your child's doctor.

Some families choose to start the cry it out method later, and that's fine. But older babies may be more set in their sleep habits and have a harder time learning to self-soothe.

How to use the cry it out method

Step 1

Establish a bedtime you'll follow every night by determining when your baby is naturally ready to go to sleep in the evening. Babies who are sleepy rub their eyes, yawn, fuss, and look away.

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Step 2

Follow your baby's regular soothing bedtime routine. This could include:

  • giving your baby a bath
  • changing your baby's diaper
  • dressing your baby in PJs
  • giving your baby a final feeding
  • reading a book
  • singing a lullaby

Step 3

Put your baby in their crib when they're sleepy but still awake. Say goodnight and leave the room.

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Step 4

If your baby cries when you leave, or if they wake at night, let them cry for as long as it takes for them to fall back asleep.

Only respond if you're worried your baby is sick or injured. (A baby monitor with video can help reassure you that all is well.) If you do need to check on your baby, leave the light off and keep your voice quiet and soothing. Don't pick your baby up. Leave as soon as you've determined your baby is okay, even if they're still crying.

Step 5

Wake your baby for their first feeding of the day at a predetermined time (for example, 7 a.m.).

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Step 6

Be consistent. The key to cry it out and other sleep training methods is following the same routine, night after night.

In most cases, babies learn to go to sleep on their own by the third or fourth night – or after a week at the most.

How long to let your baby cry it out

While it can be difficult for parents, at least the cry it out method doesn't involve much guesswork: You'll let your baby cry it out for as long as it takes them to fall asleep. For some babies, that may be 5 or 10 minutes; for others, crying may continue on and off for several hours. As long as you put your baby to bed with a full tummy and a dry diaper, and they aren't sick or injured, it's safe to allow them to cry.

If your baby wakes up in the middle of the night and starts crying, according to the CIO method you shouldn't respond. You'll only pick your baby up at a set time in the morning, for their first feeding of the day.

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That said, you know your baby best – so use your best judgment: If you're worried your baby is crying because they're hurt or sick, you can check on them to be sure everything's alright. Try to keep the check-in as brief and down-to-business as possible – avoid interacting with your baby unless there's a problem, and don't pick them up, cuddle, rock, or feed them.

If the cry it out method isn't working for your baby after a week, stop for a couple of weeks and try again. Or, consider another sleep-training method. Also, consider checking in with your baby's doctor to be sure there isn't another issue at play.

Tips for using the cry it out method

  • Set the stage for success by developing a bedtime routine and a consistent daytime schedule that includes consistent naps. Also, a sound machine in your baby's room that plays white noise can help soothe them to sleep.
  • Get help from your partner, if you have one, or a family member or friend. Make sure you and your sleep-training partner are prepared before you begin – both practically and emotionally. Be ready to support each other if you run into rough patches
  • Choose a good time that's not stressful or busy. Don't start sleep training if your partner is about to take off on a business trip, for example, or if friends are coming to visit.
  • Once you launch your plan, stick to it. Parents who've been through sleep training agree that consistency is key. Do your best to follow through for at least a week, unless you decide cry it out isn't right for your family. When your baby wakes up crying at 2 a.m., you might want to give in and hold or rock them. But if you do, you could lose any progress your baby's made and have to start over from square one.
  • Plan to lose a little sleep. Begin sleep training on a night when it won't matter as much if you miss a little sleep. For example, if you work all week, you might want to start on a Friday night.
  • Prepare yourself for a few difficult nights. Hearing your baby cry can be excruciating, as every parent knows. Go to a different part of the house or turn on some music or white noise so you don't have to hear every cry. Remember your primary objective: To give yourself and your baby a good night's rest.
  • Take a break from the crying. If your baby's crying nonstop at bedtime, let your partner take over so you can get outside for a walk or a drive. When you're refreshed, you can give your partner a break.
  • Adapt the method to fit your family. If you find cry it out too harsh, but like the general idea, you can use a more gradual approach like the Ferber method.
  • Expect relapses. Even after you've finished extinction sleep training, you can expect your child to regress occasionally, like when they're sick, when you're travelling, or when they have a sleep regression.

Does the cry it out method work?

Parents who stick with the CIO method usually find it's effective and the fastest route to improved sleep. Most babies begin sleeping through the night within three to four days, sometimes faster.

Studies have shown that cry it out sleep training helps both babies and parents sleep better. A 2006 review of 52 studies on sleep training found that the CIO method was very effective at helping babies fall and stay asleep. While crying it out worked faster than other methods, all strategies were similarly effective in the long term. A 2022 meta-analysis of 10 studies that involved several behavioral sleep techniques (including CIO sleep training) found that all methods significantly reduced children's sleep problems and improved moms' sleep quality.

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Research also suggests that the cry it out method doesn't result in long-term damage for babies. A 2020 study found that in the first year of life, extinction sleep training resulted in less problematic sleep behavior and didn't harm a baby's social or emotional development. (The study involved more than 1,000 mothers who filled out questionnaires and a subset of more than 100 mother-baby pairs who came into a lab for testing.)

Another 2020 study of 178 infants and their caretakers found that the CIO method didn't lead to behavior or attachment problems at 18 months – mirroring findings to prior research on the topic.

For some moms and dads, cry it out sleep training works just the way it's supposed to. After a few nights and some tears, their baby sleeps contentedly through the night. For other parents, when the tears continue and the promised sleep doesn't come, it's time to try something else.

No approach to baby sleep works for everyone. Just because your best friend or your sister had good luck with CIO doesn't mean it's right for you. And even if it works with your first child, it may not do the trick with your second.

Maybe you don't want to let your baby cry. Or you tried the cry it out method and it didn't work for you. There are other sleep training options: Read about no tears sleep training and fading methods for helping your baby learn to sleep through the night.

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Colleen de Bellefonds
Colleen de Bellefonds is a freelance health and lifestyle journalist. She's raising her toddler daughter and newborn son with her French husband in Paris.