As Teitelbaum previously explained to mbg, a common reason people can wake up in the middle of the night is actually a surge of adrenaline triggered by low blood sugar. When our blood sugar is low, it can cause an increase in the stress hormone cortisol, which obviously doesn’t set you up for an uninterrupted night’s sleep.
He adds that everyday stressors can cause a drop in blood sugar, too, making you both hungry and irritable (and this is especially common around bedtime, further inhibiting dozing off).
Luckily, Teitelbaum does have some advice should stress strike before bed—and in the form of a midnight snack, no less.