We know sleep makes us healthier, mentally and physically. Sleeping well increases longevity, makes us more productive, and better decision makers. Sleep contributes to stronger, more positive relationships with partners, kids, parents, friends, and colleagues.

There’s also some fascinating research showing sleep also influences our morality, our ability to think and act in alignment with our conscience, our individual and shared values, and the rules and norms of society.

How? By interfering with the cognitive processes that contribute to how we think about—and act on—our beliefs about right and wrong. Thinking and acting in alignment with our “moral compass” takes substantial effort on the part of the brain, and draws on skills such as attention, anticipation, self-awareness and awareness of others, emotional regulation and processing, and complex problem solving.

Being sleep deprived can impair these cognitive skills and interfere with our ability to make our best “right-and-wrong” decisions in our daily lives.

5 ways lack of sleep can interfere with moral decision making

Poor sleep hurts moral reasoning. Moral reasoning refers to our thinking about morals, the mental analysis we use to determine right and wrong, and the morally correct action to take in specific situations. Moral reasoning is an ability that develops over time, and it’s also an ability that varies from one individual to the next. It involves considerations of our own self-interest, the rules, customs, and laws of our society, and our own very personal ethical values. Thinking through right and wrong—and applying those thoughts to our actions—is no simple task for the brain, it requires engagement from several different areas of the brain, which involve both cognitive processing and emotional processing.

Research conducted in 2010 by Norwegian scientists examined the impact of sleep deprivation on moral reasoning in a group of Norwegian navy and army officer cadets. The scientists found that being sleep deprived significantly hurt the officers’ moral reasoning ability. Officers became less able to conduct their highest, most mature forms of moral reasoning—reasoning that draws upon deeply-seated moral principles and values. Sleep deprived, and faced with a moral decision-making task, officers were more focused on rules, and in some cases their own self-interest.

Sleep loss affects moral judgment when emotions run high. The moral dilemmas that come up in our lives are often emotionally charged. We find ourselves in the position of having to make a choice about right and wrong when we’re stressed, worried, fearful, angry. To navigate this complex decision making, the brain relies on areas of emotional functioning and cognitive functioning to work together.

Research has found that sleep deprivation makes it harder for the brain’s centers of emotion and cognition to work in connection, in making moral decisions. In a group of 26 adult men and women, a 2007 study found that when facing emotionally-charged moral dilemmas, being sleep deprived made decision making more difficult—participants took longer to arrive at their decisions when deprived of sleep. Participants were also more willing to agree with solutions that went against their own personal beliefs, when they were sleep deprived. (In this study, researchers found that people with higher emotional intelligence were somewhat less vulnerable to adopting solutions that violated their moral beliefs, when sleep deprived.)

Sleep deprivation may short-change our ability to think through some kinds of moral decision-making. The study I discussed above showed sleep-deprived people in difficult emotional circumstances taking longer to reach decisions involving moral questions. Other research has shown that for certain kinds of moral judgments, sleep deprivation may shorten the time we spend in moral decision-making mode.

Research from 2012 found that a single night of full sleep deprivation (i.e., staying awake all night), shortened the response time for making decisions involving some kinds of moral decisions—specifically, moral decisions in which the choice did not involve directly inflicting harm on another person or group of people. The researchers in this study attributed the shortened response times to the effects of sleep loss on disinhibition—not getting enough sleep can make us more impulsive, less adept at assessing risks, and can diminish our regard for social norms and conventions.

Lack of sleep interferes with our ability to anticipate problems with a moral component. A 2013 study of naval officers found that being sleep deprived compromised the officers’ ability to look ahead and foresee problems that had a moral element—situations that required some amount of “right and wrong” problem solving. (They also found the officers’ ability to anticipate tactical challenges was also compromised.) The brain’s executive functions include planning and preparation to tackle problems and challenges, and these cognitive functions are compromised when we don’t get enough sleep. This research suggests that the limits imposed by sleep loss on our ability to think ahead and plan can have an impact on our readiness to deal with right-and-wrong dilemmas when they arise.

Sleep loss may diminish our moral awareness. To make decisions and take actions in line with our ethics and values, we first must be able to recognize that a situation requires our moral attention. That’s what moral awareness is: the ability to identify that there is a moral question in front of us. Moral awareness helps us recognize the need for “right and wrong” thinking in our own choices and behavior, and it also helps us more accurately assess the ethics and morality in the behavior of other people.

Some fascinating and ingenious research from 2015 examined the impact of sleep on moral awareness. The researchers conducted three separate studies within their investigation.

The first study took place in a laboratory. Participants (a sleep-deprived group and a well-rested control group) were asked to identify the moral aspects of different scenarios. Researchers found sleep deprived participants were less able to identify the moral elements of the hypothetical situations that were presented to them. The researchers’ analysis showed a 10% drop in moral awareness among the sleep deprived group.

For their second study, researchers analyzed the web searches conducted in the US on the day AFTER Daylight Savings Time began, over a period of 5 years. (The Monday after we “spring forward” is a day when many people are sleep deprived, having lost some rest to the time change.) Researchers looked at web searches as a way to gauge conscious thinking—what was on actively on people’s minds as they were typing queries into search engines. In analyzing their data, researchers examined searches looking for a range of nearly two dozen words pertaining to morality. They found a significant decline in searches relating to morality, even though there was no decline in the overall number of web searches conducted on these days after Daylight Savings Time.

In the third study, over a 4-day period, participants recorded their nightly sleep amounts and took daily surveys designed to measure their moral awareness on day-to-day basis. Researchers found that the more sleep participants got, the higher their moral awareness was. Sleep amounts were especially strongly linked to the ability to assess the moral behavior of other people. With less sleep, people were less likely to spot unethical behavior in others.

Together, these three studies create a pretty compelling picture that going without sufficient sleep decreases our ability to identify morally questionable behavior (in ourselves and in others), and to recognize when situations need our moral attention.

We all want to be the best version of ourselves, and that includes living in alignment with our ethical values. What we’re learning from science is that sleep can help us achieve that very meaningful and personal goal.

This post originally appeared on The Sleep Doctor on August  26, 2021. It is republished with permission.