What is sleep training doing to your baby’s brain?


As a new parent, you’re sleep deprived, exhausted and confused. The pressure is on to train your baby to sleep.

If this involves leaving your baby to cry, it most likely feels awful to you – but you have been told that you will be doing yourself and your baby a favour. You may have even been told you are being ‘weak’ if you don’t teach your baby this important ‘skill’, that you’re just ‘postponing the inevitable’ or, according to one baby book, that your baby will experience a lifetime of sleep problems and insomnia if you don’t ‘teach’ him to sleep right now.

Of course you don’t want to deprive your baby of any important skills – and when you’re desperate for sleep, you’re even more vulnerable than usual. However, your own intuition can be trusted when it comes to your baby’s cries.

From pregnancy, you’re brewing a powerful cocktail of hormones that make you protective towards your baby, and this ‘chemistry of attachment’, as scientists and researchers call it, is the reason leaving your baby to cry feels so horrible to you. Your baby is biologically programmed to elicit the care she needs, and you’re biologically and chemically programmed to respond. This is why information to ignore your baby’s cries is so confusing – other people can easily dish out pretty harsh advice about your baby because they don’t have the same chemical connection that you do. 

Thankfully, you don’t have to worry that you are depriving your baby of any important skills by responding to his cries day and night. In fact, there’s increasing evidence that sleep training that requires you to leave your baby to cry can pose risks to your baby’s well-being and may have unintended negative effects on development. 

Leaving a baby to cry evokes physiological responses that increase stress hormones: unattended crying infants experience an increase in heart rate, body temperature and blood pressure. These reactions are likely to result in overheating and, along with vomiting due to extreme distress, could pose potential risks in vulnerable infants. 

And rather than learning a skill like learning to swim or ride a bike, for instance, when being left to cry ‘succeeds’ in getting a baby to fall asleep alone, it could be due to a process call a ‘defeat response’. According to neurobiologist Bruce Perry, senior fellow of the Child Trauma Academy, Houston, when humans feel threatened our bodies flood with stress hormones and we go into ‘fight or flight’. However, babies can’t fight and they can’t flee, so they communicate their distress by crying. When infant cries are ignored, this distress elicits a ‘freeze’ or ‘defeat’ response and the infant shuts down (and sleeps). 

There may also be longer-term emotional effects of leaving babies to cry. Babies need our help to learn how to regulate their emotions, meaning that when we respond to and soothe their cries, we help them understand that when they’re upset, they can calm down. On the other hand, when infants are left alone to cry it out, they fail to develop the understanding that they can regulate their own emotions.

There is also compelling evidence that increased levels of stress hormones may cause permanent changes in the stress responses of the infant’s developing brain. These changes then affect memory, attention, and emotion, and can trigger an elevated response to stress throughout life, including a predisposition to later anxiety and depressive disorders. 


English psychotherapist Sue Gerhardt, author of Why Love Matters: How Affection Shapes a Baby’s Brain, explains that when a baby is upset, the hypothalamus produces cortisol. In normal amounts cortisol is fine, but if a baby is exposed for too long or too often to stressful situations (such as being left to cry – there is evidence this doesn’t happen when a crying baby is being held and comforted), its brain becomes flooded with cortisol, and it will then either over or under-produce cortisol whenever the child is exposed to stress. Too much cortisol is linked to depression and fearfulness; too little is linked to emotional detachment and aggression.

The good news is that by responding to your baby, just as your heart is telling you, you are not only helping her feel secure, your loving interactions are hardwiring your little one’s immature brain for emotional and neurological development. Being attuned to your baby and responding to her cues helps her regulate herself, to feel safe and to eliminate those toxic stress hormones, giving her the capacity for healthy stress regulation in later life.

If you’re feeling pressured to sleep train your baby, remember this: if her sleep isn’t a problem for you, then it’s not a problem. However, if you do feel you need to make changes, there are gentle ways to help your baby to sleep without tears, for your baby and you. 

For gentle tips to help your baby (and you) sleep soundly, check out Pinky’s Baby Sleep seminars in Melbourne and Sydney, and her book, Sleeping Like a Baby, on her website