If you've been on social media lately, you've probably seen influencers talking about cortisol, the "stress hormone" and how it impacts adult sleep, hormones, and even weight. But did you know cortisol plays a big role in your baby's sleep, too?

The good news: it's not all bad. In fact, cortisol is essential for healthy development. The key is balance, and knowing how to prevent chronic overtiredness that can cause too much of it.

What is Cortisol?

Cortisol is a hormone produced by the adrenal glands. It plays a role in regulating metabolism, immune response, and the body's stress reaction.

In babies, cortisol levels naturally fluctuate throughout the day, highest in the morning to help wake us up, and lowest at night to help us sleep.

When Cortisol Becomes a Sleep Disruptor

When your baby becomes overtired (often through missing naps or staying up too long between sleeps), their body releases extra cortisol as part of the stress response.

While this can temporarily "keep them going", cue the second wind, it can also:

• Make it harder for them to fall asleep
• Cause more frequent night wakings
• Shorten naps (hello 30-40 minutes)
• Create restless, lighter sleep

Sleep Debt & the Cortisol Cycle

You might have heard the term "sleep debt", the idea that lost sleep builds up over time. In babies, sleep debt can lead to consistently higher cortisol levels, which makes it harder to catch up.

The result? A cycle of overtiredness where the baby struggles to settle, wakes more often, and misses more sleep, which in turn produces more cortisol.

Signs Cortisol Might Be Affecting Sleep

• Frequent 30-40 minute naps
• Long stretches to settle at bedtime
• "Happy but wired" behaviour in the evening
• Multiple night wakings without hunger
• Early morning wakes (before 6am)

How to Help Lower Cortisol & Improve Sleep

• Watch Wake Windows - Adjust based on your baby's age, aiming to get them down before they show strong tired cues.
• Create a Calm Pre-Sleep Routine - Dim lights, soft voices, slow movements.
• Support Daytime Naps - Contact naps, pram walks, or carrier naps are all fine if they help your baby get the rest they need.
• Get Morning Sunlight - Helps regulate their circadian rhythm (and yours).
• Keep Bedtime Consistent - Babies thrive on predictable rhythms.

Cortisol isn't the enemy - it's a normal and important part of your baby's biology. But too much, too often, from overtiredness can make sleep harder for everyone.

By focusing on timing, consistency, and a calm wind-down, you can help keep cortisol in check and make sleep easier.

 If your baby's sleep feels stuck and you're not sure how to break the cycle, we can guide you with a personalised sleep plan that works for your baby and your family - Book a Consultation Here.