In order to understand this counterintuitive reasoning, first a little background on how this whole system of sleep works.
About three hours prior to when we’re naturally prone to waking up, our bodies start secreting a hormone called cortisol, and if you’ve done some reading on your baby’s sleep prior to this, the sight of that word probably causes you to flinch a little.
Cortisol is a stimulating hormone, and is also produced in times of stress in order to elevate the heart rate and stimulate the nervous system (in case, y’know, bears) but in the morning, it’s just trying to get us started. Think of it as mother nature’s caffeine.
And if cortisol is our morning cup of coffee, melatonin is our evening glass of wine. Once the sun starts to go down, our bodies recognize the onset of night and begin to produce this lovely sleep- inducing hormone, which helps us get to sleep and stay asleep until morning, when the whole process starts over again. Melatonin production is increased and starts earlier in the evening when we awaken to some nice, bright sunlight.
But as beautifully crafted as this system is, it’s not perfect and it’s easily confused. So in the situation we examined above, here’s what’s happening...
Baby’s taking great naps during the day, which is obviously wonderful, and she’s getting lots of time outdoors, so her body’s ready to crank out some melatonin when nighttime rolls around. So what’s with that burst of energy right before bedtime?
So when baby’s body has begun producing melatonin, there’s a narrow window of time when the body expects baby to be going to sleep. After all, she’s a baby. What’s she got to stay awake for? She doesn’t watch The Bachelor and she hasn’t discovered the Internet yet.
The brain instinctively decides that something isn’t right; that for whatever reason, baby can’t sleep, (probably because, y’know, bears.) And if baby’s got a bear to run from, adding a shot of cortisol should help increase her chances for survival.
So that’s exactly what it does.
Baby’s system starts secreting cortisol and, before you know it, she’s a little bit cranked. This often shows up in the form of playfulness and an abundance of energy. In short, baby missed the window and now she’s going to have a hard time getting to sleep, but her behavior indicates anything but sleepiness.
What does all of this have to do with the dreaded 3 A.M. wake ups?
Here’s what happens... Assuming your baby’s circadian rhythm is scheduling a 6 A.M. wake up, then her body starts to secrete cortisol three hours prior to that. And at this point, the melatonin production has ceased for the night. So baby hits the end of a sleep cycle around 3:00. She gets to that “slightly awake” state, and now there’s a little bit of stimulant and no natural sedative. This, combined with a lack of independent sleep skills, means that baby’s probably going to wake up fully, and have a really hard time gettting back to sleep.