February 14, 2022 5 min read

The fact that sleep affects mood is no secret. Just think of all those times you’ve felt irritable and moody after a sleepless night. Or maybe you’ve suffered insomnia in the past and noticed how horribly it affected your well-being. You probably also know how mood-enhancing a good night’s sleep can be. 

But why exactly are sleep and mood interconnected and how exactly does one influence the other?

Research has consistently shown that inadequate sleep negatively affects mood and vice-versa. This bidirectional link is somewhat of a mystery, however. But there is some evidence that sleep and mood are influenced by the same brain mechanisms, and when there is a problem with them, both sleep and mood suffer. 

Why We Sleep

Although it’s more than obvious that sleep is essential, its actual purpose eludes scientific explanation. Scientists are still looking for answers when it comes to what roles sleep plays in our health. But there are a couple of theories: 

To recover 

Many metabolic processes take place during the day, and your body needs some time off to recover. Sleep offers a unique opportunity for the body to repair at the cellular, endocrine, and network system levels. This theory is supported by research showing that animals die within weeks of constant sleep deprivation, as well as findings that many restorative processes (muscle growth and repair and growth hormone release) occur mainly while we sleep. 

To save energy

Other theories suggest sleep is also your body’s “power-saving mode.” Or to put it differently, sleep helps your body conserve energy during those parts of the day when it was least effective for our ancestors to look for food. And since metabolism drops by around 15% during sleep, it seems quite obvious that the body takes sleep as an opportunity to conserve energy. 

To reorganize the brain

Sleep is also the brain’s housekeeping system. While you sleep, your brain clears out metabolic byproducts accumulated during the day. Sleep also plays a big role in memory consolidation and learning, with studies showing that our strongest memories form while we sleep. Brain wave changes during the different stages of sleep seem to be involved in the brain’s ability to rearrange information while you sleep.

And while many of the above processes take place during sleep, studies have only found a correlation between sleep and these processes. 

The Link Between Sleep and Mood

We’ve already explained that seep seems to play a big role in recovery, energy conservation, and learning. But sleep also plays a big part in how you feel. 

Just one sleepless night is enough to leave you feeling grouchy the next day, while getting your deserved 8 hours of sleep is often enough to put you in a good mood. One older study published in theSleep journal found that sleeping for only 4.5 hours every night for a week made the test subjects more stressed, exhausted, and moody. As expected all subjects saw a dramatic improvement in their well-being once their sleep was back to normal.

Sleep problems are also listed as a diagnostic criterion for depression and bipolar disorder in the Diagnostic and Statistical Manual of Mental Disorders-DSM. So there exists a strong link between sleep and mood. But how does science explain this link?

Well, one theory is that sleep deprivation puts the body and body in a stressed state, disrupting their normal functioning. For example, sleep disruption is associated with elevated cortisol and decreased testosterone levels. Cortisol is a stress hormone that’s associated with depressive behavior, while testosterone is known to enhance serotonin and gamma-aminobutyric acid (GABA) levels, in other words, the feel-good systems in the brain.

And the link goes both ways. Stress and abnormal mood can also disrupt sleep, leading to a vicious cycle of disrupted sleep leading to negative mood and negative mood causing sleep problems. The body responds to stress with exaggerated arousal and alertness due to perceived danger, which is not very conducive to sleep. 

Sleep Problems and Mental Health

Over 35% of all adults report sleeping less than the recommended 7 hours per night. If that really is the case, a big portion of the population is at risk of or is showing signs of poor mental health. 

As already mentioned, sleep problems are a diagnostic criterion for depression and bipolar disorder, two common mood disorders. Insomnia often precedes and even maintains depression as well as bipolar mania. In some cases, sleeping too much can be a sign of depressive illness. 

Sleep loss is associated with worsening mood in other mental health problems as well. Up to 91% of PTSD sufferers have insomnia and nightmares, for example. And research shows that sleep problems in these patients can worsen their symptoms. Anxiety disorders, schizophrenia, substance abuse disorder, and most other mental health problems are associated with poor or abnormal sleep. 

As a general rule, improving sleep can lead to improvements in symptoms in people with mental illness. Experimental and longitudinal studies, for example, suggest that not getting enough sleep can induce mania. Cognitive-behavioral therapy to treat insomnia lowers the risk of mania in those with bipolar disorder as a result. 

But there is one exception, however. Those diagnosed with depression often notice an instant improvement in their mood after a sleepless night, which has been confirmed through research. Being awake for a longer period of time seems to activate serotonergic neurons, and low serotonin has been implicated in depression. Some researchers believe this could mean that insomnia has a therapeutic effect in people with depression, as paradoxical as that may sound.

How to Sleep (and Feel) Better

If a lack of quality sleep has taken its toll on your mood, you may want to work on your sleep to see if it makes a difference. 

Sleep can be disrupted due to insomnia or a sleep disorder like narcolepsy or sleep apnea. So, to improve the quality of your sleep, you first need to figure out what is interfering with your slumber.

Most cases of insomnia are due to stress and anxiety. Both problems can be managed with self-care approaches like keeping a diary, breathing exercises, and yoga. But if you’ve been having trouble keeping your anxiety levels in check, you may want to speak to your doctor to see if you have an anxiety disorder that’s disrupting your sleep and functioning. 

Another problem that can affect the quality of your sleep despite spending sufficient time in bed is obstructive sleep apnea (OSA). OSA is a sleep disorder that leads to pauses in breathing, resulting in fragmented and disrupted sleep. One of the first symptoms of OSA is loud snoring accompanied with daytime sleepiness. Treatment is usually a combination of lifestyle interventions with continuous positive airway pressure (CPAP) therapy. But alternatives like oral appliances like the  Good Morning Snore Solution tongue-stabilizing devices are becoming increasingly popular due to their convenience and effectiveness. 





Mignot E. Why we sleep: the temporal organization of recovery.PLoS Biol. 2008;6(4):e106.doi:10.1371/journal.pbio.0060106

Sharma S, Kavuru M. Sleep and metabolism: an overview.Int J Endocrinol. 2010;2010:270832.doi:10.1155/2010/270832

Dinges DF, Pack F, Williams K, et al. Cumulative sleepiness, mood disturbance, and psychomotor vigilance performance decrements during a week of sleep restricted to 4-5 hours per night.Sleep. 1997;20(4):267-277.https://pubmed.ncbi.nlm.nih.gov/9231952/

Hanson JA, Huecker MR. Sleep Deprivation. [Updated 2021 Aug 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from:https://www.ncbi.nlm.nih.gov/books/NBK547676/

National Center for Chronic Disease Prevention and Health Promotion, Division of Population Health. CDC - Data and Statistics - Sleep and Sleep Disorders. 2017 May.https://www.cdc.gov/sleep/data_statistics.html

Maher MJ, Rego SA, Asnis GM. Sleep disturbances in patients with post-traumatic stress disorder: epidemiology, impact and approaches to management.CNS Drugs. 2006;20(7):567-590. doi:10.2165/00023210-200620070-00003

Hensch T, Wozniak D, Spada J, et al. Vulnerability to bipolar disorder is linked to sleep and sleepiness.Transl Psychiatry. 2019;9(1):294. Published 2019 Nov 11.doi:10.1038/s41398-019-0632-1

Adrien J. Neurobiological bases for the relation between sleep and depression.Sleep Med Rev. 2002;6(5):341-351.https://pubmed.ncbi.nlm.nih.gov/12531125/

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