Looks like there’s actually a really good reason so many networks have comedians hosting late-night shows: laughing producing melatonin, a hormone that helps us sleep.

In a new Japanese study, researchers had one group of nursing mothers watch a funny movie, and another group watch a “non-humorous weather information DVD.”

And while you might think the boring weather DVD might lull people to sleep, turns out that wasn’t the case — scientists who analyzed the women’s breast milk every two hours that night found higher melatonin levels in the moms who laughed their way through the comedy film.

Of course you can always buy over-the-counter melatonin supplements — but now we know a good dose of Jon Stewart may be all you need.

[Psychology Today]