For the first few years of college I maintained the typical college-student sleep schedule: in bed between 2 a.m. and 3 a.m., dragging myself up at 9 a.m. for my 9:30 a.m. lecture which I inevitably slept through (in the front row… what was I thinking?!?). While chronically sleep-deprived, I preferred spending time with my new friends and boyfriend than catching those precious zzz’s. Many of those nights made for wonderful memories, but other times I’d find myself inexplicably upset over some small issue, picking fights with my boyfriend (now husband) in the wee hours of the night.

“You’re tired, go to bed,” my wise boyfriend would tell me.

“No I’m not! This is a real issue!” sleepy me would argue back, frustrated at his disregard, not understanding why he didn’t get what I was feeling.

Now, older and wiser, I will publicly state that my husband was right—99 percent of the time I was just tired and a good night of sleep made all of my problems go away. Happily, I eventually learned the benefits of getting my requisite nine hours of sleep, and rarely find myself picking fights in the middle of the night. And now, 10 years later, I’m putting this anecdote to the test—conducting research to answer the question of whether we might, at times, find ourselves in conflict simply because one of us is tired.

Poor sleep: A route to unnecessary conflict?

Conflict is an important, inevitable, and healthy component of relationships. Romantic partners who are sharing their lives together are expectedly going to have times of disagreement. In fact, being able to express differences of opinion and find compromise may very well be the hallmark of a healthy relationship. However, conflict is not always helpful and even at its best, is generally unpleasant. Minimizing unnecessary squabbles is vital for the longevity of relationships. And here is where I think sleep comes in. People who are sleep deprived tend to experience more negative emotions (see this post for more on sleep and mood), are more reactive to negative events, and are worse at problem solving. A recipe for disaster—whereas someone who is well-rested might be able to clarify when they think they’ve been criticized, or simply shrug off a sink of dirty dishes, someone who is sleep-deprived is more likely to be a ticking time bomb, possibly reacting automatically without the capacity to stop and think it through.

In our research, we examined the link between sleep and conflict, testing three main questions:

After sleeping poorly…

  1. Are people are more likely to report experiencing conflict with their relationship partners?
  2. Is their conflict more severe?
  3. Are they less able to resolve conflict?

The short answer is Yes. A bad night of sleep is associated with more frequent, severe, and less resolved conflict between relationship partners.

After sleeping poorly, are people are more likely to fight with their relationship partners?

To answer this question we had participants complete a daily survey for two weeks. Each morning when they woke up they recorded how well and how long they’d slept the previous night. Each night before going to bed they told us whether, and how much, they had fought with their partner that day. We found that the worse people slept the night before, the more they reported fighting with their partner that day.

But is it really that people fight more after a bad night of sleep? Perhaps these people were stressed, anxious, or depressed and thus not sleeping well and fighting with their partner (that pesky “third variable” problem). We tested for this and found that the association between sleep and conflict wasn’t due to people being more stressed out, anxious, or depressed. Another possibility is that couples disturb each other in the night, so they wake up cranky after not sleeping well and their partner is to blame, creating a situation ripe for conflict. We tested this too—participants did report that their partner disturbed their sleep. But it was the lack of sleep, and not the fact that the partner caused it, that was associated with greater conflict the following day.

After sleeping poorly, is conflict more severe?

To answer our second question, we conducted a second study. We had couples come into our laboratory and spend five minutes talking about a problem in their relationship while we videotaped the conversation. How did sleep influence this conversation? People who reported sleeping poorly the previous night experienced fewer positive emotions and more negative emotions and were less able to take their partner’s perspective during the conversation, both of which are harmful to the well-being and longevity of the relationship.

We also looked at whether people were affected by their partner’s sleep. It turns out that whether or not you sleep well, if your partner doesn’t sleep well you also experience fewer positive emotions, more negative emotions, and are less able to take their perspective. So when it comes to dealing with conflict—if either partner doesn’t get a good night sleep, both partners are affected.

After sleeping poorly, are couples less able to resolve conflict?

After their five-minute conversation was over, we had each partner in the couple tell us how well they’d resolved the problem they’d just discussed. Participants were most likely to report resolving the conflict when both partners were well-rested. If either partner had slept poorly the previous night, the fight was less likely to be resolved. So once again, we found that when it comes to resolving conflict, it takes two—just one poorly-slept partner is enough to derail conflict resolution.

What do we mean by “poor sleep”?

If poor sleep is associated with negative outcomes, it is important for us to clarify what exactly we mean by poor sleep! To obtain a measure of “poor sleep” we assess several facets of sleep, including quantity (how long you sleep), quality (how well you sleep), disruptions (how many times you wake up during the night), sleep latency (how long it takes you to fall asleep), and daytime dysfunction (how tired you feel the next day). We add all of these different pieces together to get a total picture of the night of sleep. We don’t find that any one aspect of sleep is primarily associated with conflict, it is the total sleep picture.

The Bottom Line: If you find yourself more reactive than usual, think about whether you or your partner had a bad night of sleep. We don’t know yet whether these findings are causal, but it is worth considering that catching a few zzz’s might solve more problems than you’d think.


Want to learn more about sleep? Read the first three posts in this series to check whether you're getting enough sleep, have your sleep cycle revealed, and find out about how sleep affects your mood.

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