Do you ever feel like getting your child to fall asleep is impossible? You’ve created a perfect bedtime routine, read the books, sang the songs, and offered lots of snuggles….but your little one STILL won’t settle down and sleep. What’s going on here?

This post will discuss bedtime struggles from a biological perspective, looking specifically at sleep pressure and wake windows. This info will give you some tools to help make sense of your child’s bedtime struggles and determine a bedtime that meets their unique sleep needs (*hint: it might not be 7 p.m.).

Sleep Pressure and Wake Windows Are Key

Sleep pressure is a biological response in our body that builds up during the day while we are awake. As sleep pressure builds, we become more and more tired. 

As children grow, their bodies can tolerate being awake for longer periods of time; it takes longer for their sleep pressure to build. This means the time between waking up and going back to sleep gradually increases. That period of time awake is called a “wake window”. 

Wake windows will help you determine if your child has the right amount of sleep pressure to fall asleep. See below for guidelines for children ages 1-12 years old.

Age (Years)Approximate # of Hours of Sleep Per DaySuggested Wake Window
1-212-14 hours4-6 hours
311-13 hours6-7 hours (if napping)
11-13 (no nap)
4-510-13 hours11-14 (no nap)
6-129-12 hours12-15 (no nap)
*Use these wake windows as guidelines to help determine your child’s sleep needs. Remember, every child is unique!

Your Child May Be Overtired or Undertired

One of the most common reasons bedtime is such a struggle for our little ones is that they don’t have the right amount of sleep pressure. They are either overtired or undertired. 

For example: When my 3-year-old daughter has a 2-hour nap at daycare, she won’t be tired enough to go to bed at 7 p.m. But, on the days when we skip her nap, she’s exhausted and ready to go to bed by 6 p.m. 

Signs That Your Child is Overtired 

Too much sleep pressure is a common cause of sleep struggles. Overtiredness can result from:

  • Skipping or missing a nap
  • Dropping a nap too soon (not enough daytime sleep)
  • Wake windows are too long (refer to the table above)

When children awake longer than they can tolerate, their bodies release stress hormones to overpower sleep pressure. This is the body’s response to overtiredness. This is often referred to as a “second wind.”

These are signs that your child might be overtired: 

  • Clinginess
  • Increased whining/fussiness 
  • Rubbing eyes, yawning
  • Clumsy movements
  • Decreased appetite 
  • Uncontrollable giggles 

Signs That Your Child is Undertired 

An undertired child will often struggle to go to bed. There are a number of causes for undertiredness:

  • The last nap is too long
  • The last nap ends too late
  • Too much daytime sleep 
  • Early bedtime 

When a child has a nap that goes late into the day, there may not be enough time for their sleep pressure to build up before bedtime. Or, if you’re trying to put your child to bed too early, again, they might not have had the chance to build up enough sleep pressure to fall asleep. In both cases, your child is undertired, so they will have a really hard time falling asleep.

These are signs that your child might be undertired: 

  • Protesting
  • Stalling and procrastinating
  • Taking over 30 minutes to fall asleep

Use our FREE checklist to help identify why your child struggles with sleep!

A Sleep Pressure Story: Finetuning Benny’s Nap

Benny, 2 years old, and his sister, 5 years old, both wake up at 7 a.m. Because Benny was younger and used to having naps, his parents would give him a nap after he was awake for 6 hrs, from 1 p.m. to 3 p.m. They would then try putting both kids to bed at 7 p.m., but Benny would always protest and often stay awake until 8 p.m. His parents were so frustrated. Why was he fighting it so much? Shouldn’t he be just as tired as his older sister?

Turns out Benny didn’t have enough sleep pressure to fall asleep. Being awake from 3 p.m. to 7 p.m. was just a 4-hour wake window, and for Benny, it wasn’t enough time to build the right amount of sleep pressure for a 7 p.m. bedtime. 

Here are a few of the ways his parents could help him build more sleep pressure to resolve this sleep struggle: 

  • Shorten his afternoon nap.
  • Drop the nap and make bedtime earlier.
  • Keep the nap and push bedtime back later.

Because Benny couldn’t make it through a whole day without a nap, the solution was to shorten the length of the nap. They continued putting him down for a nap at 1 p.m., but would wake him up at 2 p.m. After making the switch, Benny was tired enough to fall asleep at 7 p.m. with his sister.

More Factors to Consider

Keep in mind, sleep pressure is one of many reasons kids struggle with sleep. There are many factors to consider when your child is struggling at bedtime – sleep pressure is one piece of the puzzle. Your child’s sleep can be influenced by separation, sensory, situations or transition, and nighttime fears. Since there isn’t a one-size-fits-all approach to sleep, it’s important to tune into your unique child’s sleep needs. 

If you’re ready to take a deeper dive and want a more robust resource for sleep, check out our Solving Bedtime Battles course! This course is your guide to better sleep – packed with easy-to-digest lessons, practical bedtime tools, visual bedtime schedules, and soooo much more! 

Learn more about Solving Bedtime Battles here!

Key Takeaways

  1. Sleep pressure is the feeling of tiredness that builds up while your child is awake during the day.
  2. As a child grows, they can stay awake for more time before feeling tired. This gap is called a wake window and grows as your child grows.
  3. Some signs your child might be too tired for bedtime (overtired) include being clingy, fussing more than usual, rubbing their eyes a lot, or losing appetite.
  4. If your little one seems to be stalling, protesting, or taking too long to fall asleep, they could be not tired enough (undertired).
  5. The timing of naps can be tweaked to balance the sleep pressure your child needs.
  6. Sleep pressure is only one of many reasons why a child can struggle with sleep. It’s important to remember that there isn’t a one-size-fits-all solution to sleep.


Shannon Wassenaar

Registered Psychotherapist & Mom of 1

Learn More About Shannon


Jess VanderWier

Registered Psychotherapist & Mom of 3

Learn More About Jess
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