If you're like most people whose mouths don't closely resemble a sarlacc pit, you probably brush your teeth before you go to bed. But if you're like us, you're probably lazy enough to wish there was some reason not to bother. Well, here's the thing -- it turns out that minty-fresh feeling you go to bed with every night is part of what's making it so difficult to actually shut down.
The problem isn't the brushing itself but the peppermint flavor, which for some reason they decided way back when should be the universal taste of toothpaste. Peppermint oil gives you that cool, fresh, clean sensation you crave, but it's also a stimulant that tests have shown works to enhance alertness, decrease fatigue, and stimulate the central nervous system, three things you don't want to happen when you're trying to sleep.
Santa has Tony Montana piles of the stuff to get all that shit done in one night.
There have been multiple studies about this. In one, researchers stuck a bunch of people in dark rooms and subjected them to various odors. Even after correcting for other factors (like the fact that they were presumably nervous about being trapped in a lightless, strange-smelling dungeon) they found that the smell of peppermint noticeably reduced sleepiness and increased alertness more than other smells did. Another experiment actually tested it as a performance-enhancing substance: When athletes were subjected to a variety of different smells as they worked out, those huffing peppermint had reduced fatigue and increased alertness. They were even able to complete more pushups, run a quarter mile faster, and had better grip strength.