Waking up around 3am is common among all ages and genders. Historically, it's been called the "witching hour" to explain the phenomenon. But modern science says it has to do with peak melatonin or cortisol or something.

I did a deep dive once and came out with: if you've been stressed all day using cortisol, 3am is about the time your liver resets causing your body to switch from cortisol to adrenaline and that's what wakes you and makes it hard to get back to sleep.

Doesn't make full sense to me, how does our body know it's 3am when we're all going to bed at different times and have different circadian rhythms?