The Impact of Sleep on Mood: Uncovering the Link between Unhappiness and Anxiety

Enroll in CNN's Sleep, But Better newsletter series and receive our comprehensive seven-part guide to achieving improved sleep. A recent study examining 50 years of research found that insufficient or poor sleep can significantly impact your mood and mental health.

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According to co-lead author Cara Palmer, assistant professor and director of the Sleep and Development Lab at Montana State University, all forms of sleep loss, including total sleep deprivation, partial sleep loss, and sleep fragmentation, resulted in emotional changes. The most consistent effect was a reduction in positive mood due to sleep loss. Additionally, sleep loss was found to increase feelings of anxiety and impact how people react to emotional events compared to well-rested individuals.

In particular, individuals have stated that they experienced reduced emotional arousal, which is the physical sensation of intense emotions, indicating that people generally had less intense emotional reactions after sleep deprivation.

According to the US Centers for Disease Control and Prevention, adults over 18 require a minimum of seven hours of uninterrupted sleep each night to maintain their health. Failing to meet this requirement can have serious consequences, as research has linked insufficient sleep to a higher risk of obesity, heart disease, dementia, and mood disorders.

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Despite the risks, a 2022 study found that more than 30% of adults accumulate a daily sleep debt of over an hour, and nearly 1 in 10 adults are missing two or more hours of sleep each night. "Our study shows the potential consequences of this for our emotional health, at a time where mental health problems are rising rapidly," said study co-lead Jo Bower, a lecturer at the University of East Anglia in Norwich, England.

The article "Types of sleep loss" published on Thursday in the American Psychological Association's journal Psychological Bulletin, examines data from 154 studies involving over 5,000 people spanning five decades.

In those experiments, the researchers disturbed the participants' sleep for one or more nights, whether by preventing them from sleeping (sleep deprivation), waking them up at regular intervals (sleep fragmentation), or having them wake up earlier than usual (partial sleep loss). Subsequently, the participants underwent assessments for anxiety, depression, mood, and their reaction to emotional stimuli.

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According to Palmer, complete sleep deprivation has a more significant effect on mood and emotions in comparison to partial or fragmented sleep. Interestingly, even short periods of sleep loss, such as staying up an hour or two later than usual or losing just a few hours of sleep, can affect positive mood.

Adults over 18 need at least seven hours of solid sleep at night to be healthy, according to the US Centers for Disease Control and Prevention.

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Whats going on?

The reasons for our body's behavior during sleep are rooted in the brain, according to Palmer. Prior research has shown that sleep deprivation affects the neural circuitry linked to experiencing reward and positive feelings, which is likely a contributing factor. Additionally, there are increased responses in areas of the brain associated with emotional experiences.

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The connections between the emotional centers of our brain and the prefrontal cortex, responsible for controlling emotional reactions, are disrupted. A study revealed that the loss of rapid eye movement (REM) sleep resulted in more negative reactions to emotional experiences compared to the loss of slow-wave or "deep" sleep, affecting mood in general.

Slow-wave sleep is a crucial time for the body to purge potentially harmful materials from the brain, including the beta-amyloid protein associated with Alzheimer's disease. On the other hand, REM sleep is when we dream and when information and experiences are consolidated and stored in memory. According to Bower, both stages of sleep are likely important, each playing a different role. For instance, previous research has suggested that REM sleep could be linked to processing emotional memories and may impact mood through cognitive processes.

Slow-wave sleep may be associated with the brain's reward centers, potentially impacting how people respond to positive emotional experiences. Deep sleep is considered a strong indicator of sleep quality, as it typically requires uninterrupted sleep. With each sleep cycle lasting about 90 minutes, most adults need seven to eight hours of uninterrupted sleep for optimal restoration, as reported by the CDC.

Impact on anxiety and depression

Loss of sleep also worsened symptoms of anxiety and depression, according to the study, even in people without known psychiatric or physical health conditions.

According to Dasgupta, having trouble sleeping could also be an early indicator of an underlying mental health condition.

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The real culprit behind your food coma may not be the turkey after all. According to experts, chronic insomnia could play a significant role in increasing the risk of developing mood disorders, such as depression and anxiety. Lack of sleep is said to be a major factor in contributing to anxiety, and studies included in a meta-analysis indicate that individuals with insomnia are more likely to develop anxiety disorders, and that insomnia can also predict depression.

Obstructive sleep apnea can lead to fragmented and disturbed sleep as the body can stop breathing for 10 seconds or more at a time. Dr. Dasgupta also noted that this type of sleep disorder is more common in people with psychiatric conditions and should be addressed. Additional research is necessary to understand the effects of poor sleep on individuals with mental disorders, teenagers, and children. However, Bower emphasized the importance of prioritizing sleep for everyone.