Critics of Cry-It-Out Fundamentally Misunderstand How Stress Affects the Brain (2023)

Because whether or not to sleep train can be such a fraught decision for new parents, I wanted to share my sleep training story, and to explain why, given everything we know about stress, theargument that sleep training causes long-term harmdoesn’t hold water.

Sleep Training My Son

When my son was 4.5 months old, I decided to sleep train him. Even by baby standards, my son was not much of a sleeper. He’d snooze for at most 4 or 5 hours, and then wake up every hour like clockwork, wanting to nurse but not wanting milk, popping on and off my breast and screaming in frustration.

I had gone back to work a month earlier, so napping to catch up on sleep was out of the question. Worse, I was commuting an hour to the office each way.

By then, I had reached the end of my sleep deprivation rope. I was so tired I could barely string two thoughts together. I had to coach myself through even mundane tasks like checking out at the grocery store. Say hello to the cashier. Take out your credit card. Pick up the grocery bags. Leave.

I was terrified every time I got into my car to head to work that I would nod off at the wheel and kill someone, quite possibly myself. I joked with coworkers that driver’s licenses should be temporarily suspended for new parents, but the situation really wasn’t funny.

So there I was the first night of sleep training, dripping sweat as I listened to my son’s cries. Minutes ticked by, each seeming longer than the last. I pondered whether the Ferber method included soothing every five minutes just so that you would realize only five minutes had passed.

But I was determined to stick this out, to get it done. Doing it halfway was worse than not doing it at all, I reminded myself over and over. If I were to give in, I could teach my son that crying for 30 minutes was what it took to get mommy to pick him up.

That night, he woke two more times, but never again cried more than 15 minutes. The next night, he cried for 10 minutes at bedtime, conked out, and slept until morning. That morning we greeted each other with a smile, and for the first time since his birth, I really felt like smiling at his freshly woken little face.

Although by all appearances, sleep training went well for us, some critics of cry-it-out methods would contend that I was an inadequate parent–one who had permanently harmed my son by leaving him to cry alone, uncomforted.

The Cry-It-Out Controversy

“An emotionally available parent would probably not let their baby cry it out,” claims Dr. Teti, a researcher at Penn State.

Dr. Narvaez writes in Psychology Today:

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“Letting babies get distressed is a practice that can damage children and their relational capacities in many ways for the long term. We know now that leaving babies to cry is a good way to make a less intelligent, less healthy but more anxious, uncooperative and alienated persons.”

When someone tells you that you have permanently damaged your child, it’s hard to shake off, no matter how much happier you and your baby seem once you start getting some solid rest.

Thankfully, as someone who has studied the effects of chronic stress in animals and in people, I knew that claims like Dr. Narvaez’s are not supported by data and instead rest on a fundamental misreading of stress research.

Studies on Cry-It-Out

Studies involving cry-it-out methods find no ill long-term effects for babies, and big benefits for parents. In one study, rates of depression in mothers dropped from 70% to 10% after sleep training.

Critics of cry-it-out methods argue that these studies are flawed–they don’t have the right measures of harm, they fail to determine whether the parents actually used cry-it-out methods to sleep train their babies, and they rely on parents’ reports instead of observation.

Admittedly, some of these criticisms of sleep training research are fair. Sleep training research is hard to do, especially since researchers can’t exactly force parents to sleep train little Johnny, or prevent parents from doing so.

That said, there’s no evidence in humans–none–to support the view that sleep training is harmful. If there were, we’d have heard about it.

So what the critics of cry-it-out argue, really, boils down to this: They know that sleep training is harmful, because they know stress is harmful to babies.

The problem with that argument? All stress is not created equal. We were designed to handle short-term stress. Where we humans, and other animals, run into trouble is when stress becomes chronic.

Short-Term Versus Chronic Stress

In terms of their effects, the difference between short-term and chronic stress is one not of degree, but of kind. Short-term stress enhances memory; chronic stress impairs it. Short-term stress boosts the immune system; chronic stress weakens it.

(Seeing short-term and chronic stress as fundamentally different is not just my own heterodox personal take. This is the view of people who study stress for a living, including the renowned stress neuroscientist and primatologist Robert Sapolsky, professor of Neurology at Stanford University, who writes extensively about this key distinction in his excellent book, Why Zebras Don’t Get Ulcers. The American Academy of Pediatrics emphasizes this distinction in its statement on early life stress. And the Harvard statement on child development, cited by Dr. Narvaez herself in her Psychology Today piece, makes a point of distinguishing between short-term and long-term stress.)

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The Effects of Stress in Early Life

Short-term stress mobilizes us for action–the classic fight-or-flight response. Adrenaline and cortisol pump through our veins; our bodies brim with energy; and mentally we become hyper-focused.

But these short-term adaptations are harmful when switched on for too long, especially when we are young. Scores of animal and human studies show that early life stress, such as severe early social deprivation, leads to long-term changes in the brain, cognitive and social problems, and heightened susceptibility to anxiety, depression, and drug abuse in adulthood. Chronic stress is toxic.

But from this can we conclude that all early stress, even short-term stress, is harmful?

No. Absolutely not. In studies of short-term stress early in life, occurring within the larger context of a close caregiver-infant relationship, none of these ill effects are observed.

In fact, young monkeys exposed to early short bouts of stress, such as brief periods of separation from their mothers, become more resilient to future stresses. They areless anxious and have less extreme physiological reactions tostress later in life. This phenomenon is so consistent that researchers have labelled it stress inoculation.

My Take

So where does that leave us? A little stress, even in infancy, is fine, if not beneficial, but too much for too long is very, very bad.

Do we know exactly where sleep training fits in this spectrum? Just how much stress does a baby experience during cry-it-out?

The short answer is that we don’t know for certain. Everything we do know, however, suggests that this amount of stress, in the context of a warm, loving family, is just fine.

To see why, let’s return for a second to the American Academy of Pediatrics statement on early life stress, whichprovidesexamples of the types of stress children can withstand, provided they occur within a broader context of loving, supportive relationships. These include“the death of a family member, a serious illness or injury, a contentious divorce, a natural disaster, or an act of terrorism”.By comparison, sleep training seems pretty mild.

But I would go further.I believe thatsleep training is not onlynot harmful, it is beneficial.Successful sleep training can decrease depression and chronic stress in the parents, and this benefits parents and their babies. Unlike sleep training, having a depressed mother during early childhood has been shown, repeatedly, to be linked with worse long-term outcomes for children.

Which brings me to what I find most troubling about the claims of sleep training opponents: Their zero-sum take on parenting. Worrying about your own sleep needs is selfish, they not so subtly imply. Any time you fail to put your baby’s needs before your own, you are potentially doing him harm.

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Whata narrow, cramped view of parenthood.

No one would ever dispute that parenthood entails enormous sacrifices, especially when your children are young and their need for you feels so endless and all-consuming.

But I think that because parenthood, and motherhood in particular, is so often judged in terms of self-sacrifice, we tend toforget that a primary job for parents is to be strategic.

As parents, we mustweigh short-term costs against long-term harms, because our children cannot. We have to consider the risk of a few nights of stress and unmet needs against the risk of a car accident or job loss, and against the serious physical and emotional toll of chronic sleep deprivation on the entire family.

We can forget, too, that the parent-child relationship is one not only of sacrifice but also of profound mutual benefit. You being a whole, fulfilled individual with a solid relationship with your partner, meaningful social ties, and a sense of purpose enriches your world and your child’s world. You being a well-rested, healthy, and happy parent is good for you and good for your child.


Ashokan A, Sivasubramanian M, Mitra R. Seeding Stress Resilience through Inoculation. Neural Plasticity. 2016;2016:4928081. doi:10.1155/2016/4928081.

Center on the Developing Child (2010). The Foundations of Lifelong Health Are Built in Early Childhood. Retrieved from

Crofton EJ, Zhang Y, Green TA. Inoculation Stress Hypothesis of Environmental Enrichment. Neuroscience and biobehavioral reviews. 2015;0:19-31. doi:10.1016/j.neubiorev.2014.11.017.

Darcia Narvaez. Dangers of “Cry-It-Out”: Damaging children and their relationships for the longterm. Psychology Today. 2011.

Gunnar M. Reactivity of the Hypothalamic-Pituitary-Adrenocortical System to Stressors in Normal Infants and Children. Pediatrics. September 2, 1992;90(3):491.

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Hsiao YM, Tsai TC, Lin YT, Chen CC, Huang CC, Hsu KS. Early life stress dampens stress responsiveness in adolescence: Evaluation of neuroendocrine reactivity and coping behavior.Psychoneuroendocrinology. 2016 May;67:86-99.

Lyons DM, Parker KJ, Schatzberg AF. Animal Models of Early Life Stress: Implications for Understanding Resilience. Developmental psychobiology. 2010;52(5):402-410. doi:10.1002/dev.20429.

Mindell JA, Kuhn B, Lewin DS, Meltzer LJ, Sadeh A; American Academy of SleepMedicine. Behavioral treatment of bedtime problems and night wakings in infantsand young children. Sleep. 2006 Oct;29(10):1263-76.

Parker KJ, Buckmaster CL, Sundlass K, Schatzberg AF, Lyons DM. Maternal mediation, stress inoculation, and the development of neuroendocrine stress resistance in primates.Proceedings of the National Academy of Sciences of the United States of America. 2006;103(8):3000-3005. doi:10.1073/pnas.0506571103.

Sánchez MM, Ladd CO, Plotsky PM.Early adverse experience as a developmental risk factor for later psychopathology: evidence from rodent and primate models.Dev Psychopathol. 2001 Summer;13(3):419-49.

Sanchez MM, McCormack KM, Howell BR. Social Buffering of Stress Responses in Nonhuman Primates: Maternal Regulation of the Development of Emotional Regulatory Brain Circuits. Social neuroscience. 2015;10(5):512-526. doi:10.1080/17470919.2015.1087426.

Critics of Cry-It-Out Fundamentally Misunderstand How Stress Affects the Brain (1)

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Author: Amy Kiefer

As a former research scientist and proud mama of three little munchkins, I love digging into the research on all things baby-related and sharing it with my readers.View all posts by Amy Kiefer


Is the CIO method harmful? ›

Toxic stress has been shown to affect behaviors and intelligence in older children, so researchers deduced that the cortisol increase in infants could lead to the same toxic stress outcome. They advise against all cry it out methods due to the risk of inducing high levels of stress.

Does cry-it-out raise cortisol? ›

Some parenting experts are saying “yes,” especially after new research shows that infants who were permitted to cry at bedtime had elevated levels of the stress hormone cortisol in their blood. cannot escape.

Does the cry it out method work? ›

Although it may be difficult for the first night or two, after the first initial hurdle, babies learn to sleep better on their own. The 2016 study found the cry-it-out method works. On average, the babies in the cry-it-out group slept 20 minutes longer than any other babies in the study.

Does cry-it-out impact attachment? ›

The authors' analyses showed no association between leaving infants to cry it out and infant–mother attachment at 18 months, and this conclusion received widespread media coverage.

Is Ferber method cruel? ›

Babies subjected to the Ferber method may become much more distressed during training than they were before. These so-called “extinction bursts”–which include more frequent and intense crying, protests, and tantrums—persuade some parents to give up.

Does CIO hurt baby? ›

The infants in the CIO group slept longer overall after a week and woke less overnight than babies in the other two groups. The attachment between parent and child didn't seem to be affected either way.

Is sleep training emotionally damaging? ›

Because of this “cry-it-out” sleep training can be damaging to a rapidly growing brain – and to a growing psyche. Researchers have documented how, with sleep training, infants' fight and flight instincts activate in the face of extensive distress, such as being left without comforting physical touch.

Does crying reduce or increase stress? ›

When humans cry in response to stress, their tears contain a number of stress hormones and other chemicals. Researchers believe that crying could reduce the levels of these chemicals in the body, which could, in turn, reduce stress.

What raises cortisol naturally? ›

Intense exercise raises cortisol levels, which is great if you're looking for an extra energy boost in the morning or midafternoon. But an evening or nighttime workout is not so beneficial if it's prompting insomnia or anxiety. This doesn't mean you have to ditch your evening workout if that's the only time you have.

What can I use instead of the cry it out method? ›

The pick up put down method
  • Place your baby in their crib, drowsy but awake, at a set bedtime.
  • If your baby is calm, you can leave the room.
  • If your baby begins to cry, pick them up and cuddle or rock them until they stop crying.
  • Once your baby is calm, put them back down in their crib.
  • Leave the room immediately.
21 Jun 2022

Should you ever let a baby cry-it-out? ›

Although "crying it out" as a sleep training tactic is not recommended for newborns, if you're about to start crying hysterically, it's OK to put baby down in a safe space for a few minutes to give yourself a break.

How long does the cry out method take to 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.

What happens if baby doesn't stop crying Ferber? ›

But if after a week or two, your baby hasn't made much progress or it seems like she's still crying a lot, it might be time to take a break. You could try the Ferber method again a little later on, or switch gears and try another sleep training approach.

Does sleep training cause insecure attachment? ›

One of the studies, published in Pediatrics showed that “graduated extinction” and “bedtime fading” (two common methods of sleep training) had no adverse effects on the stress response of infants, and no effects on parent-child attachment.

Why isn't the Ferber method working? ›

The Ferber method works well if you follow the plan closely. When it doesn't work, it is usually because a parent isn't actually following the actual Ferber method, like for example they are letting their child cry without checking on them or they aren't letting their child fall asleep on their own.

Is 2 hours too long to cry it out? ›

There is no set timeline for when it's too long to let a baby cry before picking them up, as long as your baby's needs are met and they are safe. If their cry changes, check on them in person or via a monitor to see if they need to be picked up and comforted.

Can excessive crying cause brain damage in babies? ›

Leach argues that recent brain research proves that babies who are left to cry for prolonged periods are at risk of suffering damage to their developing brains, which reduces their capacity to learn.

Is it cruel to leave a baby to cry? ›

A baby's development at 18 months old is not adversely affected by being left to 'cry it out' a few times or often in infancy, researchers at the University of Warwick have found.

Can babies get confused who their mom is? ›

As noted in Parenting, your baby can tell the difference between your breast milk and another mom's by scent alone. Oh, and this distinction can happen when your baby is only 2 weeks old, as further noted by Parenting. In fact, your baby can likely distinguish you from other moms even while still in utero.

What age is OK for cry it out? ›

Experts share that while various methods state you can start CIO as early as 3 to 4 months old (sometimes younger), it may be more developmentally appropriate to wait until your baby is over 4 months old. Some CIO methods go by a child's weight as a recommendation on when to start. Others go purely by age.

Why do babies cry when they see a certain person? ›

It happens as your baby develops a healthy attachment to familiar people – like you. Because babies prefer familiar adults, they might react to strangers by crying or fussing, going very quiet, looking fearful or hiding.

What are the disadvantages of crying? ›

The downsides of crying

The physical downsides of crying are pretty straightforward: puffy eyes, splotchy skin and a headachy feeling that can be chalked up to the strong contractions of your facial muscles while you weep and pressure in your sinuses from the runny nose that accompanies a tear-fest.

What happens when you cry too much? ›

If you laugh or cry uncontrollably, suddenly and frequently—even when you're not feeling emotional, this may be a symptom of a condition called PseudoBulbar Affect (PBA), which may be a sign of a neurologic condition or traumatic brain injury.

Does crying stress the heart? ›

Crying Lowers Blood Pressure

Crying has been found to lower blood pressure and pulse rate immediately following therapy sessions during which patients cried and vented. High blood pressure can damage the heart and blood vessels and contribute to stroke, heart failure and even dementia.

What foods destroy cortisol? ›

The Best Foods, Nutrients, Herbs and Supplements To Naturally Lower Cortisol Levels
  • Eat Dark Chocolate. ...
  • Drink Tea. ...
  • Eat Extra Virgin Olive Oil. ...
  • Take Cortisol-Reducing Nutrients and Herbs. ...
  • Consume Enough Food, Protein and Water. ...
  • Consume More Omega-3s and Less Omega-6s. ...
  • Get Enough Antioxidants. ...
  • Take Curcumin.
17 Apr 2022

Does oatmeal increase cortisol? ›

Multi-grain is not whole grain. In addition, even whole grains that contain gluten have been linked to cortisol production, so always choose non-gluten grains whenever possible, such as brown rice, gluten-free oats, quinoa, millet, buckwheat and amaranth if at all possible.

Does peanut butter raise cortisol? ›

Peanut butter is rich in beta-sitosterol. The plant-based sterol is necessary for brain function and has a significant impact on serotonin levels. When we are stressed, our body increases cortisol levels and the body works harder. Peanuts help lower cortisol levels and can help calm us.

How long is too long for the cry it out method? ›

There is no rule on how long you should or shouldn't let your baby cry it out. How long you let them cry should depend on the baby's age, sleep training plan, and parenting style. Surveyed parents report that cry it out takes between 30-120 minutes each night over the course of a week.

Is the cry it out method neglect? ›

Letting babies "cry it out" is a form of need-neglect that leads to many long-term effects. Consequences of the "cry it out" method include: It releases stress hormones, impairs self-regulation, and undermines trust.

Should you ever let a baby cry it out? ›

Although "crying it out" as a sleep training tactic is not recommended for newborns, if you're about to start crying hysterically, it's OK to put baby down in a safe space for a few minutes to give yourself a break.

At what age should you let a 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.

What can I use instead of the cry it out method? ›

The pick up put down method
  • Place your baby in their crib, drowsy but awake, at a set bedtime.
  • If your baby is calm, you can leave the room.
  • If your baby begins to cry, pick them up and cuddle or rock them until they stop crying.
  • Once your baby is calm, put them back down in their crib.
  • Leave the room immediately.
21 Jun 2022

Is sleep training emotionally damaging? ›

Because of this “cry-it-out” sleep training can be damaging to a rapidly growing brain – and to a growing psyche. Researchers have documented how, with sleep training, infants' fight and flight instincts activate in the face of extensive distress, such as being left without comforting physical touch.

Does sleep training have negative effects? ›

No evidence of negative effects

There are two medical studies that specifically examined the effects of sleep training on child mental health and development, both of which found no adverse outcomes.

Does leaving baby cry harm them? ›

A baby's development at 18 months old is not adversely affected by being left to 'cry it out' a few times or often in infancy, researchers at the University of Warwick have found.

What happens if you let a baby cry too long? ›

“Assuming there are no medical issues, there is no harm in a baby's excessive crying,” he says. “They may get a hoarse voice, but they will eventually get tired and stop crying. Your baby may also get a little gassy from swallowing air while crying, but that's OK.

Are babies that don't sleep smarter? ›

Science Says If Your Baby Won't Sleep Through The Night, They're Gifted. Sleep-deprived parents rejoice, there is new evidence to suggest that babies who wake up through the night are associated with higher levels of intelligence and better mental health.

Do you let baby cry it out in the middle of the night? ›

Mistake #2: Picking Your Baby Up Whenever They Cry

And for the first six months or so, you should go to them when they cry at night, so they know you'll be there and you can address their needs—but eventually, it can be helpful to give them a few minutes to see if they settle back down on their own.

How long should I let 2 year old cry it out? ›

Wait about five minutes and only enter if the crying continues. If you need to re-enter, soothe your toddler by rubbing their back until they calm down — and then leave the room. If your toddler cries again, repeat the process. Continue this method until your child falls asleep.


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