Should You Let A Baby "Cry It Out"? Here's What The Science Says

Rule one: "crying it out" isn't what you might think.


Dr. Katie Spalding


Dr. Katie Spalding

Freelance Writer

Katie has a PhD in maths, specializing in the intersection of dynamical systems and number theory.

Freelance Writer

A baby reluctant to be in a cot

Being a new parent is exhausting. It’s hardly news – but if you haven’t gone through it yourself, it might be difficult to appreciate just how demanding a brand-new baby can be. They don’t have a circadian rhythm, so forget about sleeping through the night; they wake up every few hours at random intervals, wanting feeding or changing or burping; and their only way of communicating is to scream wildly as you desperately try to figure out the problem on about four hours’ sleep.

It's no surprise that an entire global industry has grown around getting babies to sleep better. Infants are Ferberized, shushed, and patted; parents discover vanishing chairs, buy stocks in earplugs, and occasionally just give up and crawl into the crib themselves.


One of the most controversial methods of sleep training is to let the child “cry it out” – a term that’s loosely defined, but generally refers to allowing a baby to cry for some amount of time without intervening. 

Ask some parents, and they’ll call this method torturous; for others, it’s a bona fide lifesaver. But what’s the truth? What does science have to say about letting your baby cry themselves to sleep? Could it really work?

What is “crying it out”?

When you hear the phrase “cry it out,” you might have visions of parents shutting the door on a distraught newborn and not returning until the next morning, tears be damned. That’s generally not what sleep training experts advise today.

“That's not the reality of what we recommend or what parents typically do,” Jodi Mindell, a psychologist in the Department of Child and Adolescent Psychiatry and Behavioral Sciences and the Division of Pulmonary and Sleep Medicine and associate director of the Sleep Center at the Children’s Hospital of Philadelphia, told NPR back in 2019.


Modern sleep training methods are generally a little gentler than all that, she explained. “[It] doesn't matter if you come back and check on the baby every 30 seconds or whether you come back every five minutes,” she said. “If it's your first child you're going in every 20 seconds.”

Whichever method you use, there’s a big caveat: don’t start too early. 

As late as seven months after birth, babies lack object permanence: “they don't know that if you're not in the room you haven't disappeared from the planet,” University of British Columbia pediatric sleep researcher Wendy Hall explained to the BBC

At that point, any form of sleep training that involves leaving a baby to cry alone is “psychologically damaging,” Hall said. There are "a lot of people out there who just put up a shingle and start working with parents and telling them what they should or shouldn't do, without an understanding of what they're potentially doing to these babies.”

Is it bad to let my baby cry it out?

Even within these constraints, is crying it out a good idea for your baby? It’s a tricky question to answer – even though dozens of scientific studies have been carried out, relatively few of them came without fairly significant limitations and biases.

That’s not to say there’s no good information out there, though. In 2015, Hall recruited 235 families for a randomized controlled study into the effectiveness of a sleep training method known as “controlled crying” (or the slightly more dystopian-sounding “graduated extinction”), in which a parent soothes the baby for two to ten minutes, then leaves them to fuss and moan and hopefully fall asleep on their own. Should this latter miracle not happen, the parent returns to soothe the baby again, but the length of time the child is left should get longer as the evening goes on.

The results seemed to be extremely positive. “Our principal findings (adjusted for baseline) indicated a significant improvement in parents’ perceptions of the severity of the infant sleep problem, reduction in numbers of night wakes by sleep diary, increase in length of longest night sleep by actigraphy, and improvement in parents’ cognitions about infant sleep, fatigue, sleep quality, and depression in the intervention group compared to the control group,” the paper noted. 

However, were the interventions really as successful as they sounded? Look again, and you’ll see a qualification in almost all of those outcomes: they’re parent-reported. Now, there’s an obvious reason for that, which is that babies aren’t great at nuanced reflections on sleep quality – but it does have an important implication on the results. 


We’re not looking at objective measures of how well the infants were sleeping. Instead, in almost every case what was being measured was parents’ perceptions of their babies’ sleep. When we compare those with the only objective outcome listed – the actigraphy readings – it reveals something more subtle going on.

“At six weeks, there was no difference between the intervention and control groups for mean change in actigraphic wakes or long wake episodes,” explained the researchers. The fewer night wakings that were reported by parents, then, were not reflective of babies sleeping through – just babies who had learned to go back to sleep without crying.

Many other studies have found the same thing: sleep training, if it’s successful, will notably reduce the number of times a baby wakes up in the night and cries for their parent. While it’s difficult to cast “not getting woken up multiple times every night” as a bad thing, the anxious new parent might find themselves wondering: is my baby self-soothing? Or is this learned helplessness?

Well, worry not: most experts believe it’s the former. “Don't underestimate the abilities of children to self-regulate,” Hall told the BBC. “Parents can help them learn to self-regulate by giving them opportunities to self-regulate.”


“That's how you can look at self-soothing,” she added. “It's an opportunity to calm themselves down.”

Is it good to let my baby cry it out?

So, it seems letting your baby cry a bit at night probably won’t scar them for life – and it might let you catch a few extra Zs as a bonus. Should we all be sleep-training our babies like this?

Let’s face it: there’s probably a reason you’re reading this article, and it’s that if leaving a crying baby felt good or natural for everybody, it wouldn’t be so controversial. For some parents, even the promise of a vaguely normal sleep schedule isn’t enough to bear hearing their distraught child wail all night – it’s just too distressing. 

On the other hand, we’ve seen the benefits of sleep training. Without it, will these babies ever learn to self-regulate and go to sleep without a parent in constant vigil? Is it, in fact, the parents who don’t leave their babies to cry at night who are doing something wrong?


Well, the answer certainly appears to be “probably not.” In fact, whether a baby is sleep-trained or not seems to have little effect on their personality and development either way in the long-term. One randomized five-year follow-up study from 2012 found “no evidence that a population-based targeted intervention that effectively reduced parent-reported sleep problems and maternal depression during infancy had long-lasting harmful or beneficial effects on child, child-parent, or maternal outcomes by 6 years of age.”

That suggests such techniques “are safe to use in the long-term to at least 5 years postintervention,” the authors pointed out – but it also means that forgoing them isn’t going to make much difference to your kid either. Other studies have found the positive effects of sleep training can disappear even earlier, by the age of two, and nearly three-quarters of babies who regularly woke up throughout the night at five months old will sleep through by 20 months, regardless of whether they’re left to cry or not.

Meanwhile, even when successful in the short term, no method is a guarantee of a good sleeper: “I don't expect sleep-trained babies to wake less frequently,” Mindell told the BBC. “I don't always expect that they're going to sleep more on an objective measure.”

In other words: sure, not letting the baby cry may mean you get less sleep right now – but it also may not. Sleep training can be incredibly stressful, both for parents and children, and it doesn’t work for everyone. “Your child may not be ready for sleep training, for whatever reason,” explained Mindell to NPR, who put the number of these sleep-resistant babies at about one in five. “Maybe they're too young, or they're going through separation anxiety, or there may be an underlying medical issue, such as reflux.”


Maybe they’re just particularly sensitive. Just like adults, all babies have their own personalities, and it’s worth pointing out that while a link between fewer parental visits in the night and faster independent sleep could mean that crying it out is good for babies, it could also be the opposite: that children predisposed to needing help with sleep need parents willing to comfort them more often.

So it’s perfectly possible that to some parents, sleep training just isn’t worth the stress – and if leaving your child to sleep alone has some benefits, so too does the other extreme. Research has found multiple benefits of co-sleeping with your baby, including better, longer sleep for parents and child, better short-term psychological outcomes and lower stress for both, and even positive effects on milk supply.

For many, the answer may lie somewhere in the middle. “If you're rocking a baby to sleep at four months of age, they're waking once a night, it's working for the family, why would you mess with success?” Mindell asked. “Why would you do sleep training? [...] We only really recommend it when there's a problem.”

The verdict

So, should you let your baby “cry it out”? The answer really boils down to one question: do you want to? 


As long as your baby can cope with it – remember, sleep training isn’t thought to be beneficial before six months old, and shouldn’t be used on babies who have been through trauma or are anxious or sensitive – and as long as you can cope with it, too, have at it. You’re unlikely to do any permanent psychological damage to the child, and you might get a good night’s sleep for yourself out of it too.

However, if you don’t want to sleep train your baby, that’s fine too. Eventually, they’ll learn to go to sleep whatever you do – and they’re unlikely to want to sleep in your bed for long once they realize how terminally uncool parents actually are.

“Parents are looking for like what's the most effective method [to get the baby to sleep],” Mindell told NPR. “But what that is depends on the parents and the baby.” 

“It's a personalized formula,” she added. “There's no question about it.”


All “explainer” articles are confirmed by fact checkers to be correct at time of publishing. Text, images, and links may be edited, removed, or added to at a later date to keep information current. 


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