Lying awake staring at the ceiling while your partner sleeps soundly could be a reflection of your relationship.
A new study shows the most content couples tend to have the same sleep cycles but when a wife isn't happy in the marriage, they'll fall out of sync.
Researchers from the University of Pittsburgh found that when couples are happy, they are usually asleep and awake at the same time about 75% of the time.
When a wife reported higher marital satisfaction, the couples spent even more time on the same sleep cycle.
"Most of what is known about sleep comes from studying it at the individual level," said lead author Dr Heather Gunn, from the University of Pittsburgh.
"However, for most adults, sleep is a shared behaviour between bed partners.
"How couples sleep together may influence and be influenced by their relationship functioning."
The study involved 46 couples who wore an actigraph unit to measure their sleep cycles over 10 days and also completed a relationship assessment.
"The sleep of married couples is more in sync on a minute-by-minute basis than the sleep of random individuals," Dr Gunn said.
"This suggests that our sleep patterns are regulated not only by when we sleep, but also by with whom we sleep."
The study was published in the journal Sleep.