There’s a reason brand-new parents are universally exhausted — it’s normal for a newborn to sleep for only a couple hours at a stretch.

But if your baby isn’t falling asleep on her own or sleeping six hours straight by the time she’s between 4 and 6 months old, you might be interested in learning about sleep training.

One of the most straightforward ways to sleep train your baby is with the "cry it out" method (CIO). It's not for every family; as the name suggests, it involves tears (baby's, and probably yours, too).

If you're unsure about the idea of letting your baby cry, it can be reassuring to keep the ultimate goal in mind: helping your little one learn the essential skill of falling asleep on her own and soothing herself back to sleep when she wakes during the night.

What is the cry it out method of sleep training?

Cry it out, also known as the extinction method, is a sleep training technique that involves putting your baby in her crib fully awake and allowing her to fuss or cry until she falls asleep — without help from you. That means you won't feed to sleep, rock to sleep or use any other crutch to get your baby to drift off. 

The point of all sleep training methods isn’t to keep a baby from waking up during the night (everyone does, even adults), nor is the goal for baby to get through the entire night without a feeding (breastfed infants might continue needing a feed up to age 1). The goal is simply to teach baby to fall asleep on her own, outside of your arms. 

Tips on letting baby cry it out

While it might seem hard to believe, crying it out is most likely much harder on you than it is on your baby.

Before you get started, make sure that baby’s not napping too much or too little during the day, since overtired babies have a harder time falling and staying asleep.

You’ll also need to establish a bedtime routine that doesn’t involve feeding or rocking to fall asleep.

Ready to try the CIO method? Here's how:

  • Look for your baby’s cues that she’s tired. She might rub her eyes, suck her thumb, pull at her ear or get cranky at the same time every night. Anticipating when your baby needs to sleep is crucial to CIO success, to ensure you get baby in bed before she’s overtired.
  • Start your 30- to 45-minute bedtime routine. This helps your baby wind down and prepare for sleep. Good baby bedtime routines often involve a bath, final feeding, a book, lullabies and maybe a massage.
  • Put your baby down in her crib every time. Whether for bedtime or naps, the crib (and not a stroller or swing) is conducive — not to mention safe — for sleep and helps establish a routine.
  • Always put baby down while she's still awake. The goal of sleep training is to give your baby the opportunity to learn how to fall asleep on her own, which requires being awake and not rocked to sleep. Give her a gentle pat and softly tell her you love her, then leave the room without waiting for her to fall asleep.
  • Expect some protest. Your baby will probably cry, maybe even a fair bit. However long you leave baby by herself, it'll likely feel much longer.
  • Don’t respond. Here’s where the going gets tough: The full-on cry it out method calls for you to let baby cry, without comfort from you, until she gets tired and falls asleep.

You're going to have a rough couple of nights (or even a week or more) as you listen to your baby wail. But remember this as you're sitting outside her door, thinking you're the worst parent in the world: Crying won’t hurt your baby in the long run. Ultimately you're doing your baby a favor by helping her learn to fall asleep on her own.

How long should you let baby cry it out?

The goal of the CIO method is to let baby fuss and cry on her own until she eventually wears herself out and falls asleep on her own. In the beginning, you may end up having to let baby cry it out for 45 minutes to an hour before she goes to sleep, though it varies from baby to baby.

Most parents who try the cry it out method find their babies cry increasingly less over the first three nights and their crying virtually ends somewhere between the fourth and seventh nights.

Eventually babies may simply fuss or screech in complaint for a couple of minutes — or simply quietly fall asleep.

When to let baby cry it out

When to let your baby cry it out depends on your baby and your comfort with the method. Babies are generally developmentally ready to be sleep trained at 4 to 6 months. By about 5 to 6 months, they can sleep through the night without needing to eat, making it a good time to try the CIO method.

Keep in mind that your older baby may have already trained you to respond to her nocturnal tears with feedings, cuddling and even a visit to your bed. By 6 months, babies are wise to the fact that crying often results in being picked up, rocked or fed — pretty good motivation to keep on doing it.

If that's the case, sleep training will require some changes for both baby and you. But once they get the message that you’re not buying their act, most will give up the crying game, usually within three or four nights, sometimes longer.

Should you let baby cry it out for naps?

If you’re trying the CIO method at nighttime, you should let your baby cry it out for naps too. 

But if your baby’s naptime is typically on the shorter side and only lasts 30 minutes or so, you may want to limit how long you let her cry (to around 10 minutes) before you try another sleep training method or even give up on the nap for that day.

After about a week of nighttime sleep training, naptimes should get easier. At that point your baby will have gotten used to the idea that being put in her crib means that it’s time to sleep. And she will have discovered the self-soothing methods (pacifier, thumb-sucking, etc.) that help her to summon the sandman.

What's the difference between the CIO method and the Ferber method?

Ready to try sleep training with your child, but looking for a gentler option that involves (slightly) fewer tears than the CIO method? The Ferber method might be for you.

The cry it out (or extinction) method of sleep training involves putting your baby in bed and letting her cry until she falls asleep without any comfort or help from you.

The Ferber method is a form of "graduated extinction" sleep training where you allow your baby to cry for a few minutes, then check back in to quietly comfort her for a minute or two, gradually increasing the amount of time you leave her by herself until she’s asleep.

The theory was outlined in the 1985 book Solve Your Child’s Sleep Problems by Dr. Richard Ferber, the former director of the Center for Pediatric Sleep Disorders at Boston Children's Hospital.  

When to stop letting baby cry it out

As long as you know your baby is in a safe sleep environment (i.e. in her crib, on a firm mattress without any pillows, bumpers, blankets or stuffed animals) and isn’t hungry, wet or sick, it's okay to leave her alone to settle down on her own.

If you’re concerned about her safety, peep in — but keep any interaction brief. A video baby monitor can be reassuring.

Try to give the CIO method enough time to see if it makes a difference. Stick to a consistent routine for a full two weeks before giving up on it altogether. 

Also keep in mind that a big change or stress in your baby’s life, like a move, new sibling, new babysitter, ear infection, etc., can render sleep training futile. Wait a few weeks until things have gone back to normal before attempting sleep training.

Cry it out isn't for everyone, and it doesn’t work for every baby. And that's perfectly okay.

If CIO makes you extremely uncomfortable, remember that it isn’t the only option. You may want to start with another form of sleep training, like the Ferber method of graduated extinction, to see if it works better for you.

What to do if your baby spits up or throws up when crying it out

A small number of babies get so worked up from the cry it out method of sleep training that they spit up or throw up. Fortunately, it isn't technically a health concern, though it can be upsetting and stressful. It also may indicate that your baby is sick or that this isn't the right method or approach for your family.

Talk to your pediatrician if it happens repeatedly to rule out anything medical and get advice on whether you should keep trying or change gears. If there isn't an actual health reason behind it (and you can stomach it), the vomiting usually stops after a few nights at most.

But if it doesn't, don't force it. Stop sleep training for a few weeks and check in with your doctor to get advice on how to proceed and see if there's another method better suited for your little one. And avoid feeding baby too close to bedtime, which can disrupt sleep regardless. Instead, try to nurse or bottle-feed during the first part of her bedtime routine rather than the last.

Criticism of crying it out

CIO critics sometimes point to a 2012 study finding that babies' levels of the stress hormone cortisol remained high even after they stopped crying and went to sleep on their own.

But that study was small (limited to just 25 babies between 4 and 10 months old) and had no control group to define what the study's author meant by "high" — meaning the babies in the study could have had elevated cortisol levels simply because their parents were putting them to sleep in an unfamiliar environment.

What's more, the study looked only at the extinction, "pure" form of cry it out, where parents don't go in at increasingly longer intervals to soothe their babies, but instead let them cry for a long stretch all at once (a method that still does work for some families but isn't the only way to sleep train).

The American Academy of Pediatrics (AAP) published its own long-term, larger study in its journal Pediatrics advocating sleep training as healthy and important when it comes to babies' development.

The research showed that babies sleep trained either using the gradual, Ferber method or the straight CIO method were not at a higher risk of emotional, behavioral or psychological problems by age 6.

When to call the doctor

If your baby seems to be getting extremely worked up and/or is crying so much she's getting sick, it’s worth checking in with your pediatrician to make sure there isn’t another underlying medical problem and this method is right for you and your little one.

You should also ask for guidance if your baby doesn’t respond to cry it out sleep training after about two weeks or so. Your doctor may be able to offer other tips to help both of you sleep better or steer you in a different direction.

No matter what you wind up doing to establish good bedtime rituals and sleep habits in your baby, just know that the days of nighttime feedings and wakings are numbered. Before you know it, your baby will be sleeping for increasingly longer periods at night as she grows. And then you can all get the rest you need.