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Key points
- In a culture where long work hours are rewarded and distractions abound, sound sleep is often elusive.
- Sleep deficiency has been linked in the literature to a host of negative health outcomes.
- Sleep is closely linked to emotion regulation.
In a culture like ours, in which long work hours are expected and pleasurable nonstop distractions abound, sound sleep is often hard to come by. Our society promotes hard work as a path to happiness and self-fulfillment, and many people believe they can learn how to get by on little sleep with no ill effects.
No wonder so many of us are sleep-deprived. Data indicate that more than 30 percent of adults and 90 percent of teenagers get less than the recommended amount of nightly sleep. According to the Centers for Disease Control and Prevention, about one in three U.S. adults reported not getting enough rest or sleep every day. Nearly 40 percent of adults report falling asleep during the day without meaning to at least once a month, and an estimated 50 to 70 million Americans have ongoing sleep disorders.
This is problematic because sleep problems have been linked in the literature to a host of negative outcomes, including injuries, loss of productivity, and poor decision-making, as well as many chronic health problems, including heart disease, kidney disease, high blood pressure, diabetes, stroke, obesity, and an overall greater likelihood of death. An extensive NIH report (2006) concludes: “After decades of research, the case can be confidently made that sleep loss and sleep disorders have profound and widespread effects on human health.”
Sleep, in other words, is more important than most people appreciate.
Sleep and Psychological Well-Being
Psychologists have long been particularly interested in the link between sleep and psychological well-being. A vast literature has accumulated attesting to the link between sleep and emotion. Yet sleep is a complex and mysterious process, the intricacies of which are yet to be fully understood. Sleep problems, for example, come in various forms that may not have similar effects. Moreover, some aspects of emotional health and well-being may be more vulnerable to sleep disruptions than others.
A recent (2023) article by Cara Palmer of Montana State University and colleagues seeks to offer some clarity on the effects of various sleep deficiencies on emotional health. The authors meticulously reviewed findings from more than 50 years (1966-2022) of sleep research to assess the impact of troubled sleep on various facets of mental health and functioning. Their study “represents the largest, most comprehensive meta-analysis to date quantifying the impact of sleep loss on domains of human emotional functioning.” The authors looked at three distinct sleep issues:
- Sleep deprivation, measured by studies that ask participants to stay awake for extended periods with no intermittent periods of sleep.
- Sleep restriction, measured by studies that shorten typical sleep duration for one or more nights.
- Sleep fragmentation, measured in studies that force awakenings during a night of sleep.
The authors focused on studies that measured the effects of sleep problems on several important emotional outcomes, including positive and negative affect, general mood disturbance (in studies that did not measure positive and negative emotions separately), emotional reactivity (valence and arousal), anxiety, and depressive symptoms.
The authors included in their review only studies in which participants were free of psychiatric or sleep-disorder diagnosis as well as any medical conditions known to impact sleep and/or emotional functioning. They included only experimental studies with adequate control groups and those that measured at least one emotion-related dependent (outcome) variable.
Overall, the final meta-analysis included 146 peer-reviewed studies and eight unpublished studies or data sets (e.g., dissertations) with a total number of 5,717 participants across 28 countries.
Findings From a Review of Research
Eighty-five studies looked at sleep deprivation (SD). Results showed that SD influenced mood (increased negative and reduced positive emotion and increased general mood disturbance) and anxiety but had no significant effect on depressive symptoms. The effects on emotion and anxiety showed a dose-response relationship—that is, more wakeful hours led to more disrupted emotion.
Fifty-six studies looked at sleep restriction (SR). Like SD, SR had a significant effect on both positive and negative emotions, as well as mood disturbance and anxiety outcomes, with dose-response effects for positive emotion. “Positive affect decreased gradually as sleep duration decreased. The largest deficits in positive affect occurred around 4 hours of sleep.” SR was also found to affect depression.
Twenty-one of the included studies used sleep fragmentation (SF). SF was found to be linked to decreased positive affect and decreased arousal.
The authors conclude:
“The strongest and most consistent effects of sleep loss were observed for decreased positive affect, followed by increased anxiety symptoms, and blunted arousal in response to emotional stimuli. Effects on other emotional outcomes were varied and less consistent… All forms of sleep loss, including SD, SR, and SF, reduced positive affect, with the largest effect size found for SD… These findings should inform regulations and policies that directly impact sleep–wake patterns including maximum work periods and schedules (e.g., for surgeons, truck drivers), school start times, military/combat operations, daylight savings time, and investment in education and health care that prioritizes sleep.”
The review contains several limitations. For one, sleep studies by nature find it difficult to fully mask participants to their condition, which may have produced expectancy effects.
Moreover, lab experiments are inherently low on what psychologists call "ecological validity," because conditions in the lab do not resemble real-world conditions. In addition, the literature reviewed mostly relied on young adult samples, which may not represent the population at large. Further, existing studies relied mostly on subjective reports rather than objective measurements of emotional states.
Finally, other aspects of sleep that were not addressed in this review may be important to consider as we hone our understanding of sleep and its health effects. For example, a recent study (2024) by Australian psychologist Daniel Windred and colleagues suggests that sleep regularity, rather than sleep duration, is key for predicting future health.
Still, the bottom line from converging sources of evidence is that adequate, uninterrupted, regular sleep is an essential agent of emotional and physical well-being. The good news is that potent behavioral interventions for improving sleep exist, and improved sleep can often be achieved without much expense, delay, or noxious side effects.
Bang for your buck, protecting your sleep is without a doubt among the best things you can do to improve and maintain your mental health and well-being. Psychologists should regularly include sleep hygiene assessment and intervention in their care plans. If your psychologist does not inquire about your sleep habits, they are not providing you with top-notch care.
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