So, what’s really the secret to wedded bliss? Some couples swear by separate bathrooms, weekly date nights and never going to bed angry. But according to researchers from the University of Pittsburgh, a well-rested spouse is key to keeping a happy marriage.

The researchers said wives who have trouble falling asleep are more likely to report negative interactions with their husband the next day.

But in typical ying-and-yang fashion, husbands who were shortchanged in the sleep department actually had a rosier outlook for the new day.

For the study, scientists recruited thirty-five healthy, married couples and had them wear movement-monitoring sensors for ten nights.

During the day, spouses kept diaries detailing how strongly they felt positive things, like how close they felt to their spouse, whether they discussed their feelings and whether they felt valued.

They also kept track of arguments and how much they felt criticized, dismissed or ignored.

Not surprisingly, when women didn’t get enough shuteye, they were more likely to report a higher number of negative, rather than positive, interactions with their spouses the next day.

Curiously, though, husbands’ sleep problems didn’t seem to darken their day, the implication being that whatever interfered with their sleep the night before may have been, shall we say, emotionally uplifting.

This study is the first of its kind to show that sleeplessness can directly put a damper on emotions.

Previous studies have shown that difficulty sleeping and emotional problems often go hand in hand.

But the question becomes whether poor sleep contributes to emotional upsets, or whether emotional strife keeps people awake at night.

The latest findings seem to suggest that poor sleep comes first, and emotional upsets follow.

So the solution for a happier marriage, it seems, is to hit the hay early — after, of course, airing grievances and making up. Then just sleep on it.