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  • Heather Wallace


Updated: Jul 16, 2023

Part One: The Science of Crying and Self-Soothing in Newborns and Infants

What is the most common reason a parent decides NOT to sleep train? Even when they are absolutely exhausted? It’s the crying. The intense, brain-triggering crying that the parent KNOWS is going to start up as soon as they lay that baby down in the crib awake. And I don’t blame parents for trying out EVERY possible solution before jumping into sleep training. “Maybe my baby is overtired!” “Maybe I just need better black out curtains!” “Maybe if I put rice cereal in my infant’s bottle at bedtime she will sleep longer.” (*Note the AAP advises against putting anything other than milk in a bottle due to a choking hazard [7].) Once a parent has gone through the long list of reasons why their baby is waking 383749 times a night or insisting she be held for every nap, one might entertain the thought of sleep training. But wrapping your head around allowing an infant to cry indefinitely, until the baby falls asleep is a great feat. However, it doesn’t have to be as scary as your brain is screaming at you that it is, once you dig deep into the purpose of crying, the process of learning to fall asleep, and why our brain goes haywire when we hear an infant (not even our own!) cry.

What Our Brains and Bodies Do When We Hear a Baby Cry

Studies have shown that when a person hears an infant crying the part of their brain responsible for fight-or-flight is triggered (1). This will cause us to jump up and run to our infant to assess the infant’s needs. If we DON’T go to our babies immediately our heart starts to race, anxiety takes over our thoughts, and our breathing becomes fast and shallow. Humans don’t particularly like sitting in these feelings, so it’s more likely that we will get up and engage in some way to soothe the baby to the point of stopping the crying. This seems healthy and natural, serving a purpose of driving the parent to action in order to protect their infant. But…protect them from what exactly? We aren’t hunters/gatherers who have left our infant alone back at the hut, nor do we sleep outside amidst dangerous animals and warring tribes. Your baby is safely nestled in a sleep space where decades of research and evolving regulations has shaped it into one of certain safety.

I was fascinated with the research I found regarding infant crying and I was almost angry that society teaches us that crying is bad. How many of us had parents that inadvertently, or even intentionally taught us that? Should we blindly listen to this instinct to rush to our baby’s side to check breathing and perform a circus act to calm the baby down? Let’s look at what a baby’s brain and body is doing when something triggers the baby to cry.

Crying Triggers the Parasympathetic Nervous System and Releases Oxytocin

When I started my journey researching crying when it came to sleep training I wanted to answer the question, “Is crying inherently bad? If it isn’t, what purpose does it serve?” Since I don’t hold a PhD. in neuroscience, I’m sure there could be some biases and misinterpretation of the research on my part, however I did my best to read the research impartially. I was fascinated by the analysis of qualified researchers when it came to this subject.

Crying in infants has a biological function that developed when the world was much different than it is now. One reason for this crying is “inter-individual”, or social in nature. When we cry in front of others it can elicit an empathetic response from those around us, which can actually aid in emotional regulation and self-soothing. In other words, we feel good because our friends and family gathered around us and lifted us up in a difficult time. However there is a second reason for crying, which is “intra-individual”, or affecting the person’s physiological state. Crying in itself triggers the Parasympathetic Nervous System (“PNS”) which is responsible for reducing stress and bringing the body back to a state of rest. (see this blog post about how the PNS is responsible for rest-and-digest!). The PNS is also said to be responsible for releasing the important hormone oxytocin, which is responsible for a euphoria-like feeling (2). Interestingly, the PNS is split between two nerves, the ventral vagal system which promotes social engagement (for example, a parent coming to try to reassure the infant), and the dorsal vagal system which supports rest-and-digest (3). With the PNS developing by the end of the second trimester in utero (4), your baby could have the capability of taking the route of “self-care". Your dedication to connecting with your baby builds her ventral vagal system, which your baby engages when regulation is needed.

The Release of Hormones in Tears and the Increase in Oxygen to the Brain

As you know, when a baby cries, tears are released. These tears, called “emotional tears”, are different from tears produced to protect and moisten the eyes. They actually have higher levels of hormones in the tears which help bring your baby’s body back to homeostasis (5) (homeostasis is essentially a normal or baseline level).

The vocalizations and sobbing that you hear from an upset baby can also increase oxygen levels in the brain which slows the heart-rate and lowers body temperature. "The deep belly breaths of crying also activate the parasympathetic nervous system (which helps you recover from stress), regulating your blood pressure, heart rate, and breathing." (8)

The Rhythmic Pattern of Crying and the Ability to Shut Out Overstimulation

The rhythmic pattern of a baby’s cry has been said to promote self-soothing (2). Babies often like the rhythmic features of rocking and patting. But with these two ways of soothing being attached to something external, the baby cannot access these ways to soothe himself anytime he needs it. Therefore, babies find specific ways to soothe themselves if it is not happening externally. Your baby may rub his head back and forth on the mattress, kick his legs up and down, scratch at or feel the sleep sack, or play with/pull at hair. (perfectly normal!) I have found that a younger baby will find her fist or thumb to rhythmically suck on to self-soothe, however an older baby learning the skill for the first time will roll around and have more self-soothing attached to movement and vocalization (babbling after the crying stops!). In the end, the rhythmic pattern of crying to self-soothe tends to get replaced by these other ways once the baby learns to access them consistently.

Babies often cry between sleep cycles. They don’t particularly like that they’re awake but they’re just working on getting back to sleep. It doesn’t necessarily mean this is a cry for intervention. I often think when a baby is crying as we enter the bedroom and put the sleep sack on before sleep a baby is saying, “Yes! I’m tired! I need sleep!” According to the American Academy of Pediatrics, crying helps “shut out sights, sounds, and other sensations that are too intense to suit her,” (6). They instinctively do what needs
to happen to regulate themselves and use crying to do so.
Does your baby exhibit any of these behaviors in the crib? Click to Save!

Conclusion: No, Crying is Not Bad!

After my research I feel confident that I answered my query of whether crying in itself was bad…whether we should be placing these expectations on ourselves as parents to immediately drop what we are doing and run to comfort a crying baby. If you’re a second-time parent you know that’s just not feasible. And I promise, second-born babies are just as securely attached and healthy as first-borns in this area!

What I am not saying is to never comfort, soothe, reassure, hold, or rock your baby. There is continual comfort from you as the parent when you look into your baby’s eyes and speak lovingly to her, or when you pick your fussy baby up off the floor to change activities due to her call for attention. When your baby is running a fever and just not feeling well, you’re going to cuddle and rock your baby to provide soothing. Even when you just want some baby snuggles, you can pull your baby up into your arms and settle in to sing a sweet song or read a book. But when it comes to sleep especially, if we continue to provide something external to help the baby self-soothe, a baby’s brain will not form an association with soothing and these internal processes. A baby can only learn to soothe themselves when they are not being soothed by someone or something else (rocking of the swing, sucking on the pacifier, or Mom patting baby’s back for example). This is why part of sleep training (or “untraining”, as Janet Lansbury calls it!) is taking short breaks in intervention/soothing to give the baby a chance to mimic that feeling on their own. It’s kind of like an “I do”, “We do”, “You do” approach to teaching the baby how to soothe himself! The first few weeks of a baby’s life it’s all “I do”. You are rocking, holding, using all the props to soothe the baby to sleep. When it’s time to release the reins a bit, you will do a mix of allowing your baby to practice self-soothing, and soothing your baby completely to sleep when times call for it. And lastly when you feel comfortable with letting go completely, much like that moment when you’re teaching your child to ride a bike, you can be present with your baby while not doing the work for her.

Though we can’t always stop or block all crying, and we shouldn’t, we can tap into the logical part of our brain and go through the checklist of what the baby could be crying about- hunger, pain (such as reflux, gas, or teething), wet or dirty diaper. These things can be attended to. A baby could be crying because he is tired, or even overtired, or overstimulated. These reasons for crying can be met with empathy and validation, “You’re tired! You had such a fun day, and now it’s hard to sleep.” Your baby may be crying out of protest because he was enjoying playing with sister, or he just isn’t tired enough (in which case reviewing his schedule needs is important to decrease crying going forward). You can lovingly reassure your baby with gentle, rhythmic touch and calm verbal validation. This touch and calm voice may not, probably not, stop the crying. Your baby has to do that through the process of finding his internal methods of soothing. Reassuring your baby in intervals that both promote self-soothing and continue connection will help your baby learn to meet that need of falling asleep on his own.

Coming Soon!

In my next blog post I will dive into sleep training and attachment, as well as how that attachment helps the baby cope with the temporary increase in stress levels associated with sleep training. (Spoiler alert! The few days of sleep training does not negate the weeks and months you have spent anticipating your baby’s needs and building connection, and the connection you have built buffers the baby from long-lasting effects of stress.)

If this blog post has encouraged you to start the sleep training process, or start teaching healthy sleep habits to your newborn, check out my services to see how I can help you reach your goal of a well-rested baby.

(2) Is crying self-soothing? (Though this fascinating article does not have a definitive conclusion, the main objection to the hypothesis that “crying is self-soothing” is that negative feelings and judgements surrounding crying such as embarrassment and humiliation can mitigate the positive physiological self-soothing effects of crying.)
(5)The purpose of emotional tears (the difference between basal tears, reflex tears, and emotional tears)


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