We knew this, but now it's been studied. First-time parents who get more sleep have better relationships with each other.
They measured actual sleep (with "continuous writs actigraphy," which I'd never heard of but Google is very familiar with and seems to mean they put a thing on your wrist that measures how much it moves during the night, and they figure if you wrist is moving, or maybe moving in certain ways, you're awake), which they say predicted the relationship much better than reported sleep.
Yup. going without sleep makes you cranky and depressed.