If you’re navigating baby sleep training, you may have heard concerns about cortisol, often called the "stress hormone." Some parents worry that sleep training could cause a harmful rise in cortisol levels, leading to long-term stress or emotional challenges. But what does science really say? Let’s break it down.
What is Cortisol, and Why Does It Matter for Baby Sleep?
Cortisol is a vital hormone that plays a key role in regulating sleep-wake cycles, metabolism, and immune function. It follows a natural rhythm, peaking in the morning to help wake us up and gradually declining in the evening to support sleep.
When babies cry—whether from hunger, discomfort, or adjusting to a new sleep routine—their cortisol levels may temporarily rise. This is completely normal! The body is designed to handle short bursts of increased cortisol as part of its natural stress response.
But does this mean sleep training is harmful? Let’s explore what research has found.
Cortisol and Crying: What the Research Really Says
Crying is a baby’s primary form of communication, and it’s expected during sleep training as they learn to fall asleep independently. Some temporary increase in cortisol is natural—but does it cause long-term harm? Science says no.
🔹 A major study in Pediatrics followed infants who underwent sleep training and compared them to those who did not. The result? No long-term differences in cortisol levels, emotional well-being, or parent-child attachment—even five years later!
🔹 The BBC reported on another study showing that while controlled crying may lead to a temporary cortisol rise, these levels normalize as babies adjust to their new sleep patterns. Importantly, there was no evidence of long-term emotional or behavioral harm.
In other words, while sleep training may involve short-term adjustments, it does not cause chronic stress or emotional damage.
The Long-Term Benefits of Healthy Sleep
On the flip side, chronic sleep deprivation can negatively impact a baby’s ability to regulate cortisol, leading to fussiness, difficulty settling, and even long-term sleep struggles. Research has consistently shown that babies who learn independent sleep skills:
✅ Sleep longer and more peacefully
✅ Experience better mood regulation
✅ Have improved cognitive and emotional development
✅ Benefit from well-rested parents who can be more patient, present, and engaged
A study published in the Journal of Pediatrics confirmed that behavioral sleep interventions have no negative impact on a child's development or parent-child relationship—even years later.
By helping your baby develop healthy sleep habits, you’re setting them up for success, not stress.
How to Approach Sleep Training with Confidence and Support
If you’re worried about sleep training, the key is to find an approach that feels right for your family. You don’t have to choose an all-or-nothing method—there are many gentle, supportive ways to help your child develop strong sleep skills:
💡 The “Stay in the Room” Method: Stay in the room and offer reassurance as your baby learns to fall asleep independently.
💡 Leave and Check Sleep Training: Parents pop into the baby’s room offering reassurance, helping your baby adjust at their own pace.
💡 Custom Sleep Plans: Every baby is different—finding a strategy that works for your child is the most important factor.
The adjustment period is temporary, but the benefits of healthy sleep last a lifetime.
Need Help? Let’s Create a Sleep Plan That Works for You
I’ve helped over 500 families teach their babies to sleep through the night, and I can help yours too. Sleep is a foundation for your child’s growth, well-being, and your family’s overall happiness.
🌙 Ready to make sleep a reality in your home? Book a free discovery call, grab my free sleep guide, or join my next webinar. Let’s get your family the rest they deserve!