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I don’t need to tell you that lack of sleep makes you testy, irritable, and short-tempered. We all know, through experience, how sleep deprivation puts us on a short fuse.
Still, as with the cognitive impacts of sleep deprivation, most of my patients don’t realize how deeply sleep deprivation—especially when chronic—hurts their emotional well-being, affecting their mental health, their outlook and performance, and their relationships.
Sleep deprivation makes you more emotionally reactive.
Whether snapping at a co-worker, getting into a fight with your partner, or losing your cool with your kids, not getting enough sleep increases the likelihood that your emotional responses will be more impulsive and intense. None of these situations are fun or contribute to healthier, happier relationships. But emotional reactivity goes beyond being cranky. That same hair-trigger that makes us irritable with the people around us can be exhausting and draining, leaving us feeling at the mercy of our emotions and critical of ourselves for not being more adept at managing them.
Even a single night of sleep deprivation sets us up to react more strongly and impulsively to negative or unpleasant situations, according to research. And when operating with chronic sleep debt, as so many busy adults do, you contend with this heightened emotional reactivity on a daily basis.
We’re still learning about the ways that sleep and emotion are connected. But we do know some pretty interesting things about how sleep deprivation affects the complex emotional centers of the brain, making us more likely to overreact or lash out in anger and frustration.
Research shows that sleep deprivation increases activity in the amygdala—the emotional rapid-response center of the brain. This part of the brain controls many of our immediate emotional reactions. When short on sleep, the amygdala goes into overdrive, causing us to be more intensely reactive to situations. Interestingly, it’s not only our negative emotions, like anger and fear, that get a heightened response. Studies show that, when sleep-deprived, we’re more reactive across the whole spectrum of emotions, positive and negative.
At the same time that the amygdala is fired up, lack of sleep also hampers the communication between the amygdala and the prefrontal cortex, another area of the brain involved in emotional regulation. This part of the brain handles a lot of complex tasks, and one of them is to put the brakes on impulsiveness. The prefrontal cortex is like a traffic cop for emotions: It sees an impulsive reaction and says, “Whoa, slow down, do you really need to be going so fast?”
When you don’t get enough sleep, this part of your brain can’t do its job as well, and you become more impulsive and less thoughtful in your emotional responses.
We all go through emotionally-charged experiences every day and throughout our lives. Those experiences get stored in the brain as memories—and sleep plays an important role in processing those memories. REM sleep in particular appears to be especially important in processing painful and difficult memories. This process helps ease the emotional sting these memories can have. It also helps your emotional mind return to a less-charged, more neutral state. This nightly emotional reset is important for your ongoing mental health.
REM sleep occurs in a series of episodes over the course of a night’s sleep. As the night progresses, episodes of REM get longer, with most REM occurring in the last third of the night. When your sleep is shortchanged, your brain doesn’t get the benefit of this restorative work, and your emotional life can suffer.
You have a more negative outlook.
Knowing how our brain’s emotional centers are affected by lack of sleep, it’s not difficult to imagine how sleep deprivation can contribute to a more negative mindset. Sleeping poorly makes us focus more on the negative, and increases what psychologists call repetitive negative thinking. That’s when your mind is stuck in a negative place, going over the same frustrated thoughts again and again. Repetitive negative thoughts are intrusive, difficult to control, and can have a major impact on how you feel and function. They’re also linked to the development of the mood disorders depression and anxiety.
A new study shows that sleep-deprived people have more repetitive negative thoughts, and are less able to control their minds’ fixation on the negative than their better-rested counterparts. Scientists also found that the greater the sleep deprivation, the more difficult it was for people to turn their minds away from ruminating on negative thoughts, feelings, and experiences. No one would ever choose to have a mind that’s trapped in a cycle of negative thinking. Unfortunately, when you’re chronically short on sleep, that’s what happens—and it can be a difficult cycle to break.
You worry more about the future.
Sleep deprivation exacerbates emotional reactivity and fearful responses and creates an often-intractable negative outlook. It also makes us worry more. Recent research shows that when we’re sleep-deprived, we worry more about the future—especially if we’re prone to worry in general.
Scientists at the University of California, Berkeley conducted a fascinating study, in which they found that sleep deprivation increases our tendency to worry about the future—a form of worry that scientists call anticipatory anxiety. We’ve known for a long time that sleep deprivation increases anxiety and contributes to anxiety disorders. (In turn, anxiety makes sleep more difficult.) Their study provides some important new insight into more precisely how lack of sleep aggravates the brain’s worry response.
The researchers observed brain scans of 18 healthy young adults as they looked at images containing both emotionally disturbing and emotionally neutral content. To stimulate anticipatory anxiety, scientists gave participants a signal ahead of viewing individual images, letting them know they were about to see a disturbing image. The scientists observed and measured brain responses among participants, both when participants were well rested and when they were sleep-deprived.
Brain activity in response to the anticipatory signal was much higher when the participants were sleep-deprived than when they were well-rested. Again, it was the emotional control centers of the brain that were activated by lack of sleep and contributed to increased anxiety about the future.
Sleep deprivation triggered more anticipatory anxiety in people who were already prone to be worriers, the researchers found. If you tend to worry, getting plenty of rest is especially critical for maintaining a healthy emotional balance and avoiding the development of chronic anxiety.
You feel less connected to—and thankful for—your partner.
Sleep deprivation doesn’t only affect our individual emotional well-being. It also undermines healthy, satisfying relationships. I’ve talked about how sleep deprivation can sink a healthy sex life. It also can interfere with other forms of intimacy between partners.
Of course, being emotionally more reactive and focused on the negative isn’t likely to improve anyone’s relationship. But sleep deprivation also directly affects how we perceive and treat our partners.
Scientists at UC Berkeley found that lack of sleep diminishes gratitude for our romantic partners. One really interesting aspect of this study: It only took one person in the relationship to be short on sleep for both partners to feel a diminished sense of gratitude toward each other. Your partner’s poor sleep can make you less appreciative of them, even if you aren’t lacking sleep yourself.
Sleep deprivation also diminishes our capacity for empathy, an emotional skill critical to healthy relationships. Empathy is the ability to understand another person’s feelings, thoughts, and experiences.
Researchers recently studied the effects of sleep on emotional empathy and found that, when sleep-deprived, we’re less able to demonstrate empathy for others. That means we’re less able to see things from another person’s point of view and less able to recognize and imagine their feelings. This aligns with other research showing that sleep deprivation impairs our ability to accurately recognize emotions in other people.
These skills of self-awareness, appreciation for others, and empathy are essential parts of our emotional intelligence—and sleep deprivation impairs them, often weakening our bonds of trust and communication in the relationships that are most important to us. Studies show couples that are sleep deprived fight more and resolve conflicts less successfully than well-rested partners. And it only takes one person in a couple to be short on sleep to increase conflicts.
Women and men experience sleep-deprived emotions differently.
As with other aspects of sleep deprivation, men and women appear to experience some of the emotional impact of poor sleep differently. I led a study a few years ago that investigated how much sleep men and women need. Our study found that women experience more anger, more hostility, and more depression first thing in the morning than men do. We know that overall, women’s brains expend more energy than men’s do. Most scientists chalk this up to women’s ability to multitask. That additional energy expenditure means women need more sleep, to restore full, healthy function to their brains. When they don’t get the full amount of restorative sleep they need, emotional difficulties can arise. They arise for men, too—but women’s may occur more quickly or more often, because of their particular sleep needs.
Sleep’s relationship to our emotional lives is another important example of why it is a necessity, not a luxury. Your mental and emotional health—and your relationships with others—depend on getting plenty of high-quality rest.
