Why Do We Need Sleep? Sleep Deprivation, Brain Functioning, And Your Mental Health
Like food and water, routinely getting a good night’s sleep is vital for humans to survive, supporting our body's healing ability, cognition, emotional regulation, and more. A lack of quality sleep can impair functioning in these areas, significantly affecting well-being in many ways. Below, we’ll explore some of those impacts more closely and provide suggestions for improving your sleep habits to support overall health.
Restorative sleep vs. non-restorative sleep
Not all sleep is created equal. Restorative sleep is considered the ideal—a type of rest that allows your body to repair and refresh itself, leaving you feeling rested upon waking. The most restorative sleep occurs during REM (rapid eye movement) and deep sleep stages (sometimes called stage three of the non-REM sleep cycle). Without enough stage-three sleep, you’re more likely to feel tired or depleted.
Keep in mind that restorative sleep isn't the same thing as sleep duration. One may get many hours of sleep but—due to sleep disturbances, for example—still miss the sleep cycles necessary for restorative rest.
Why do we need sleep for physical health?
Restorative sleep is essential for physiological functioning in several ways. Without it, a person might be at higher risk for conditions like heart disease, high blood pressure, obesity, diabetes, stroke, and infections. Restorative sleep also plays a significant role in helping the body conserve and store energy.
Cellular repair and growth
During deep sleep, the body repairs damaged tissue and regenerates cells. The primary mechanism behind this process is the growth hormone (GH) secretion surge that occurs during deep sleep and stimulates cell division and protein synthesis. During this time, the body heals itself from injury and grows new muscle. Restorative sleep is essential for repairing DNA damage commonly associated with regular, day-to-day stressors.
Immune system support
Not only does sound sleep allow the body to repair itself, but it also produces inflammation-fighting proteins called cytokines. These proteins enhance the body's ability to fight viruses, infections, and other illnesses. Additionally, restorative sleep may lessen allergic reactions and even help the body respond to vaccines more efficiently.
Restorative sleep and cognitive functioning
The quality of sleep we get or don't get is also closely tied to cognitive health. Deep sleep supports our ability to learn, remember, create, regulate emotions, and much more. Many of the same mechanisms that drive the relationship between restorative sleep and the body’s ability to heal and defend itself from damage are also responsible for supporting brain health.
Quality sleep for memory consolidation and learning
Slow-wave sleep (SWS), deep sleep, and REM sleep play a significant role in effective memory retention and learning. During those phases, the brain replays and fortifies memories to be stored long-term.
Different sleep stages are associated with different memory functions. For example, SWS has been linked primarily to consolidating facts and events, while REM sleep might play a role in emotional memory.
Why do we need sleep for focus, attention, and decision-making?
Sleep quality and quantity also affect our concentration, learning, creativity, problem-solving abilities, and overall mental performance. REM sleep is often associated with boosting creativity too—in particular, the brain’s ability to connect thoughts and ideas that drive innovation and decision-making. SWS facilitates restorative functions that help with focus and attention during waking hours.
Sleep and brain detoxification
During sleep, the brain’s waste-removal system (called the glymphatic system) flushes out waste products and toxins accumulated between brain cells, a process critical to overall brain health and functioning. While this mechanism may also be active during waking hours or light sleep phases, it's most effective during deep sleep. Without this detox process, studies suggest that the brain may become more susceptible to neurodegenerative conditions like Alzheimer’s disease.
Restorative sleep and mental health
Ample research reveals that sleep and mental health are closely interlinked. For example, studies suggest that REM sleep helps the brain process emotional memories, potentially reducing intrusive memories and helping us manage our responses to negative experiences over the long term.
In addition, sleep disturbances and depression tend to share a cyclical relationship. Depression often leads to poor-quality rest (too much or too little sleep), and poor sleep may increase the risk of or worsen depression.
A variety of other mental disorders have also been linked with sleep problems. Some examples include anxiety disorders, post-traumatic stress disorder, schizophrenia, bipolar disorder, and attention-deficit/hyperactivity disorder (ADHD).
What causes sleep problems?
Somnology, or the study of sleep, has made significant strides over the past few decades in understanding the mechanisms and functions of sleep. Somnology research also explores what might cause sleep problems. Here are a few examples of factors that may disrupt normal sleep and contribute to sleep problems, according to research in this field:
Lifestyle factors such as shift work, jet lag, alcohol or caffeine consumption before bed, stress, and caregiving
Poor sleep habits such as not keeping a regular bedtime routine, sleeping in less-than-optimal conditions (too much light/noise), and excessive screen time before bed
Sleep disorders like insomnia, sleep apnea, restless legs syndrome, and narcolepsy
Medical conditions like chronic pain, thyroid disorders, cancer, diabetes, asthma, and disease of the heart, lungs, and digestive systems
Mental health conditions like anxiety, depression, post-traumatic stress disorder (PTSD), and obsessive-compulsive disorder (OCD)
Medications such as certain antidepressants, stimulants, and corticosteroids
Other factors: like age, genetics, and sex assigned at birth
Not enough hours of sleep: the consequences of sleep deprivation
How much sleep we get can affect the body’s natural sleep-wake cycle. Not enough can lead to problems with physical, mental, and emotional functioning. For example, people who don’t get enough sleep may have trouble regulating their emotions and behavior, making decisions, and coping with change. They may also have difficulty with memory and diminished problem-solving.
In addition, sleep deprivation has been linked to impaired judgment, leading to an increased risk of injury in car crashes and other accidents and a higher chance of falls and broken bones in older adults. In the long term, people who are sleep-deprived may be at higher risk of certain chronic conditions (obesity, diabetes, heart disease) and have a higher likelihood of developing mental health disorders as well.
How many hours of sleep do we need for optimal brain health?
Ideal sleep patterns for a given individual depend on several factors, including age, genetics, and lifestyle. Here are general sleep recommendations by age as outlined by the US Department of Health and Human Services:
Infants (up to three months): 14–17 hours per day
Toddlers (one to two years): 11–14 hours per day
Preschoolers (three to five years): 10–13 hours per day
School-aged children (six to 12 years): nine to 12 hours per day
Teenagers (13–18 years): eight to 10 hours per day
Adults: seven or more hours per day
How do I know if I’m experiencing sleep deprivation?
While it’s common to wake feeling sluggish and tired sometimes, if you feel that way most days, you might not be getting enough sleep. Frequent yawning, marked afternoon drowsiness, and nodding off when you're at rest, such as when watching a movie, reading a book, listening to a speech or presentation, or having a conversation, are common signs of sleep deficiency. You might look for mood changes, reduced alertness, and memory problems too, and people experiencing sleep deficiency might also notice increased appetite—particularly for higher-fat and lower-protein foods.
Tips for better quality sleep
Changing your sleep schedule for the better can be challenging, depending on a few factors. For example, the more sleep-deprived you are, the longer it might take. The reasons behind sleep disturbances can make a difference, too. For example, someone overcoming jet lag that’s causing trouble falling asleep might return to normal sleep after a few days, whereas some people with insomnia may not adjust to a regular schedule without professional help. It may take time, but it is possible to establish lasting healthy sleep habits with consistency and, when necessary, professional intervention. Here are some suggestions for promoting better rest:
Create a sleep routine in which you go to bed and wake up at the same time every day, including on weekends and vacation days.
Make your bedroom sleep-friendly by keeping it dark, cool, and quiet. Some people use earplugs, blackout curtains, or a white noise machine.
Avoid electronics before bed, and try to turn off screens 30 minutes or more before bedtime.
Avoid large meals, caffeine, and alcohol in the late afternoon and evening.
Avoid intense exercise right before bed—but do try to get some exercise every day. Studies suggest that people who exercise daily may sleep longer, be less likely to have sleep disorders, and experience better sleep quality.
Spend time outside during the day to help regulate your circadian rhythm.
Engage in relaxing activities before bed, such as taking a bath, meditating, reading, listening to quiet music, or using breathing techniques.
Better quality sleep through better mental health
Stress and sleep disruptions can often be linked to varying degrees. For example, stressful life events like job loss, divorce, or the death of a loved one can contribute to short-term insomnia lasting for days or weeks. Coping healthily with such stress may help individuals get their sleep schedules back on track. Chronic and ill-managed stress, however, might lead to more persistent sleep problems. Persistent sleep problems can then contribute to mental health conditions like depression and anxiety disorders, which cause more sleep issues, creating a cyclical relationship that can be hard to break.
Seeking mental health support for sleep challenges
If you're experiencing persistent sleep challenges that may indicate the presence of a diagnosable sleep disorder, it's generally recommended that you meet with your doctor or a sleep medicine specialist. They can evaluate your symptoms and provide a diagnosis and treatment, if applicable.
In addition, many individuals turn to cognitive behavioral therapy (CBT) to find relief for sleep challenges. CBT is one of the most widely used talk therapy methods for treating mental health challenges, but a specific form of it—known as cognitive behavioral therapy for insomnia—is also typically the first treatment recommended for certain sleep challenges.
CBT works by helping individuals change their perspective on depressive and anxious thoughts by identifying and reframing them into more realistic, positive ones. Research suggests that CBT may reduce chronic insomnia symptoms by about 50% in many people, and its effects may last for two years or more.
Exploring the option of online support
Despite its potential effectiveness, not everyone with insomnia and the mental health challenges it may cause gets the help they need. The reasons for this are varied. Some might have difficulty finding a therapist in their area or have time constraints that limit their availability to attend sessions. Others may assume treatment isn't affordable or won't work for them.
For many, internet-delivered CBT for insomnia offers a solution to such barriers to treatment. Online therapy platforms connect users with a large pool of mental health professionals experienced in using CBT to treat insomnia, anxiety, depression, and other mental disorders. These platforms may then match an individual with the right provider for their needs. Next, people using online therapy can attend sessions virtually on a schedule that fits their needs—all from the comfort of home. Additionally, online therapy can be often more affordable than in-person therapy without insurance.
Current research indicates that internet-delivered CBT can be an effective alternative to in-person CBT for many. For example, one 2023 study measured treatment outcomes for individuals participating in a smartphone-based CBT program for insomnia. Their findings suggest that the program was “effective in improving insomnia severity and sleep-related parameters, both alone and combined with sleep medicine.”
Takeaway
Humans need sleep for many reasons, from supporting the ability to make decisions and regulate emotions to the function of healing the body and promoting brain health. Sleep deprivation can lead to many health complications and can be caused by underlying physical health challenges, mental health challenges, and/or poor sleep hygiene. Not everyone struggling with sleep issues will also experience mental health challenges, and vice versa—but the two are so commonly linked that they are often treated using the same psychotherapeutic techniques. In addition to meeting with your doctor, getting support from a therapist experienced in CBT for insomnia may be beneficial.
Why does sleep feel so good?
Sleep often feels good because it is a natural restorative process. When brain waves slowdown in deep sleep, the brain tends to store memories and get much needed rest, which can make a person feel refreshed the next day. There are several theories about why sleep is important, including the energy conservation theory. Research published in Physiology of Sleep states, “Energy conservation theory posits that the main function of sleep is to reduce a person's energy demand during part of the day and night when it is least efficient to hunt for food. This theory is supported by the fact that the body has decreased metabolism by up to 10% during sleep.” Another theory about sleep is brain plasticity theory, which posits that sleep is needed for development of brain structure and function.
Is 20 hours without sleep bad?
Occasionally going 20 hours without sleep may not lead to serious health problems. However, it can affect concentration and make a person feel sleepy during the day.
Are sleeping pills bad for you?
Sleeping pills may lead to drowsiness, dizziness, and difficulty thinking the next day. Also, some sleeping pills can have side effects, such as headaches, digestive problems, and dry mouth. However, a doctor may be able to prescribe a sleeping pill that works well for you without causing significant side effects.
Is 2 hours of sleep better than no sleep?
Two hours of sleep is typically better than no sleep, though it usually isn’t enough to allow you to function at your best. Two hours of sleep may be enough to allow you to get through a whole sleep cycle involving stages of rapid eye movement sleep and non-rapid eye movement sleep (NREM). Researchers on sleep and brain activity believe that, during rapid eye movement sleep, dreaming occurs and your brain processes emotional experiences and consolidates memories. Typically, the body cycles back to NREM sleep, when eye movements slow. For your brain and body to function properly, you typically need several cycles of sleep during a typical night, but two hours of sleep may provide enough time for at least one cycle.
Why does your body not let you sleep?
Trouble sleeping may be related to numerous factors. Some people may experience a sleep disorder or a medical condition that makes it difficult to fall asleep. Others might have stress or a mental health condition that makes it hard for their body to sleep.
Why is sleep so important for mental health?
Sleep can be fundamental for brain basics in human beings. For example, sleep can affect how nerve cells in the brain communicate with each other. Research also suggests that sleep serves a role in removing toxins from the brain, which can contribute to healthy brain function and improve mental health.
How does lack of sleep affect mental health?
A lack of sleep can affect the nervous system, which can affect a person’s mental health. Chronic sleep deprivation may increase a person’s risk of anxiety and depression. Oftentimes, problems with sleep lead to irritability and difficulty managing life stressors.
How do you tell if you need more sleep?
There can be a number of signs that a person needs more sleep. For example, excessive daytime sleepiness and irritability may signal that a person is not getting enough quality sleep.
Is it unhealthy to sleep during the day and be awake at night?
Whether a sleep pattern is healthy may depend on a person’s schedule. Some people may have to sleep during the day because of shift work. However, being awake at night can be detrimental if a person has to follow a traditional daytime schedule.
How do you recover from missing a night of sleep?
After missing a night’s sleep, you might find that it’s best to avoid napping the next day. You might try to continue your daytime routine, including exercise, but not in the evening. Late exercise can raise your body temperature, which typically lowers in the evening to prepare the body for sleep.
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