Sleep and Mental Health: Why Our Brains Need Sleep

Understand how sleep impacts the mind and the link between sleep disorders and mental illness

By Alesandra Woolley

Sleep for the brain is like gas for a car. When the tank is full we get where we need to be. But as time goes on, the gauge falls lower and lower until the gas is gone and the car stops. Without the fuel it needs, the car is useless.

Our brains operate in a similar way. The only difference is the brain’s fuel is sleep. Without proper sleep, our minds begin to slow, unable to operate at their full potential. This happens until the mind becomes so deprived of the rest it needs, it breaks down. And without the commander-in-chief acting accordingly, the rest of the body pays the price.

In this guide, we are going to deep dive into the complex relationship between sleep and mental health, including how these two aspects of health are inversely related, the consequences of sleep deprivation on the mind, and the link between sleep disorders and mental health disorders.

You ready? We’re really about to exercise your mind.

How Sleep Impacts Mental Health

Sleep is the mind’s time to rest and recharge. When we get proper sleep, memories, emotions and new information are processed and filed away for our minds to retrieve later on. You know, so you can recall the name of the new coworker that started in your office last week. If you fail to get adequate sleep, well, let’s just hope you don’t run into that new coworker in the bathroom. Because sleep is the time our mind blocks for mental processing, it makes sense why we would be forgetful when we miss out on a good night’s sleep. That’s not all. Sleep is also the time emotional processing takes place. This is why if we miss out on precious rest, we are far more likely to silently curse the car who cuts us off in traffic, or worse.

While these may seem like comical examples of sleep deprivation’s effects on the brain, unfortunately, the consequences are much more severe than forgotten names and road rage.

Consequences of Sleep Deprivation on Our Psychological State

The mechanisms of sleep disruption and mental health are complicated to understand. But what scientists do know is that sleep and mental health are intimately related. After all, it’s during sleep that we process our emotions and memories.

Think about it like this: sleep for the mind is like the quiet hours at the office. When there is less to respond to, you get more work done. Same goes for the brain. When we are asleep, the brain can really get to work because it doesn’t have to respond to all the external stimuli we encounter when we are awake. But if we rob the brain of this precious time, we pay the price.

Here are a few of the primary consequences sleep loss has on our psychological state.

Emotional Instability

Mood after a night of too little sleep.

Mood the night after too little sleep.

Have you ever noticed that when you miss out on sleep you tend to be more sensitive, easily irritated, or impulsive? There’s a biological reason for that, and it has to do with two areas of the brain called the amygdala and prefrontal cortex.

The amygdala is in charge of our emotional responses. But to do its job correctly it needs us to sleep, because that’s the time it’s allocated to process emotion. When we miss out on sleep, the amygdala goes into overdrive, causing our immediate emotional reactions to intensify. In fact, one study using MRI brain scans showed that the amygdala was around 60% more emotionally reactive in participants who were sleep deprived compared to those who were well rested. Hence, why you are more prone to road rage after a night of poor sleep. It’s not only negative emotions that intensify with lack of sleep; positive ones do too.

That’s not all. The amygdala isn’t the only area of the brain that gets hit with the consequences of sleep deprivation. Another area involved in emotional regulation, the prefrontal cortex, does as well. The prefrontal cortex does a lot of impressive things. One of which is being “the voice of reason” to our emotions (aka putting the brakes on our amygdala when it’s being a diva). The prefrontal cortex helps control our impulses.

However, like the amygdala, the prefrontal cortex can’t do its job properly when we don’t sleep well. Much of this has to do with a disruption in communication between the amygdala and prefrontal cortex, who work closely with one another. This makes us more impulsive and less likely to think through our emotional reactions, which is a dangerous place to be.

The disruption of the amygdala in combination with the prefrontal cortex is what makes us more vulnerable to mood swings, erratic behavior, and increased emotional reactivity when we lose sleep. This is also why all parents dread when their teenager comes home from a sleepover.

Hormone Disruption

In addition to emotional instability, scientists know that lack of sleep causes a chemical imbalance in the brain. Some of the most valuable chemicals in the brain are our hormones.

Our body produces and regulates roughly 50 different hormones which act as chemical messengers for the brain, traveling through our blood and delivering messages from the brain to different areas of the body. Hormones influence appetite, weight, mood, immunity, growth, healing, and much more. In a word, hormones (amongst other things) allow us to function properly.

However, lack of sleep messes up the communication between the brain and it’s messengers, causing our hormones to act incorrectly or deliver misinformation to the body. This is why sleep deprivation poses such a dangerous threat to mental health—there’s a lot at risk if our hormones don’t deliver the correct information across the body.

Hormone disruption caused by lack of sleep is mainly due to how sleep affects the endocrine system, particularly the hypothalamus which is attached to the pituitary gland. The endocrine system consists of several glands that secrete (aka produce) hormones. The mastermind behind the endocrine system is the hypothalamus.

The primary responsibility of the hypothalamus is to maintain balance in the body, including hormonal balance. It tells the glands of the endocrine system when to produce certain hormones and when to regulate others. Put another way, the hypothalamus tells the hormones what messages to communicate to the body and when. Much of this critical instruction from the hypothalamus is given during sleep.

At night, the hypothalamus instructs certain glands of the endocrine system to physically produce the following hormones and regulate others. But if we don’t sleep, it can’t deliver the proper information causing everything to fall out of balance. This puts our bodies in a state of chaos trying to find homeostasis again.

Although many hormone levels are influenced by sleep, cortisol (the hormone that impacts stress levels) has one of the biggest impacts on the state of our mental health.

Less Sleep, More Stress

Cortisol is a steroid hormone produced by the adrenal glands that plays a big role in our “fight or flight” response. It helps keep us alert. The production of cortisol is regulated by the pituitary gland (remember, the one the hypothalamus is connected too). It’s very important for cortisol levels to be just right. If too much or too little cortisol is produced, there are consequences.

Unfortunately, when we don’t get enough sleep, too much cortisol is produced. This puts our body in a constant state of stress, unable to relax. This is the reason individuals under a lot of stress struggle with insomnia—the increased amounts of cortisol keep them awake!

We know stress has a number of detrimental effects on the body, including impaired thinking, weight gain, and the inability to control emotions. The worst part is, sleep deprivation and stress contribute to a negative feedback loop that can be difficult to break and often results in mood disorders, anxiety disorders, and depressive disorders.

With heightened stress, comes heightened anxiety which can make you hypersensitive to all sorts of physical, mental, and emotional stimuli. For anyone diagnosed with mental health disorders or sleep disorders, additional stress can increase the severity.

Our mind is pretty complex, huh? Amazingly, this is only scratching the surface in terms of how sleep impacts our mental health. But what about how our mental state impacts sleep? That’s a whole other fish to fry. I told you our sleep and mind have an intimate relationship.

How Mental Health Impacts Sleep

There’s no denying sleep and mental health have a reciprocal relationship. Lack of sleep impacts mental health, and vice versa. One thing is for sure: when our mental health is on the rocks, our sleep is right there with it.

Research shows Americans with psychiatric conditions are far more prone to sleep issues and abnormal sleep habits. In fact, chronic sleep problems affect 50 to 80 percent of patients in a typical psychiatric practice, compared with 10 to 18 percent of adults in the general U.S. population. So what’s the connection between mental illness and sleep disorders?

Mental Illness and Sleep Disorders

Traditionally, clinicians believed sleep disorders were a symptom of mental illness. Now, current research suggests sleep problems may raise risk for, and even directly contribute to, the development of some psychiatric disorders. But it’s not that simple. The link between sleep health and mental health is stronger and more complicated than ever.

It’s important to note that the relationship between these two ailments varies in severity and complexity across different disorders. One mental illness may develop in part due to a specific sleep disorder, but it can also be a symptom of the same mental illness — creating a positive feedback loop. Some mental issues may show no causal relationships with sleep at all. And some sleep disorders have no relationship with mental disorders whatsoever.

The most common mental illnesses in the United States are anxiety and depressive disorders, affecting roughly 40 million American adults, of which 50 to 90 percent also have a sleep disorder. The most common sleep ailments for individuals with mental illness are insomnia (not being able to sleep) and hypersomnia (sleeping too much), with sleep apnea following close behind.

While the relationship is complex, here’s what we know for a fact:

  • Sleep disorders are more common among the mentally ill
  • Lack of sleep can worsen mental illness and make it more difficult to cope with symptoms
  • It’s very likely that treatment for sleep disorders will alleviate symptoms of mental health disorders
  • Those with mental health disorders often spend time in lighter, less restorative stages of sleep than deep, REM sleep, which is critical to health and healing

The relationship between lack of sleep and mental illness is particularly important to understand because it has the potential to become very dangerous when untreated. A University of Michigan study found a strong correlation between insomnia and suicide.

Common Mental Illnesses and Their Associated Sleep Disorders

Anxiety Disorder

Anxiety disorders are the most common mental illness across the United States, affecting 18 percent of the adult population. Anxiety disorders typically develop from a number of risk factors including genetics, brain chemistry, and life events. The good news is, anxiety disorders are highly treatable.

Common Sleep Problems Associated with Anxiety Disorders
  • Insomnia
  • Hypersomnia
  • Nightmares
  • Night time panic attacks

Anxiety is a reaction to stress. While all of us experience and react to stress, the nervous system of those with an anxiety disorder fails to reset back to normal after fighting or fleeing the stressor. A heightened state of stress and anxiety keeps the nervous system alert, unable to relax enough for you to fall asleep. This is why insomnia is a common companion to anxiousness. Individuals with anxiety might also find themselves battling hypersomnia or oversleeping, as a response to the exhaustion from insomnia.

When anxiety is caused by trauma, such as PTSD, it’s not uncommon for them to relive that trauma through a vivid, unsettling dream that jerks them out of sleep. For those with panic anxiety disorder, it’s not uncommon for them to experience nocturnal panic attacks which take place during the lighter stages of sleep. The individual wakes up feeling extreme panic or fear, perhaps accompanied by sweats, pains in the chest, and increased heart rate.


Depression

Depression is a mood disorder that is far more severe than just feeling sad. We all experience low points, trying times, or stressors that bring our mood down—that is completely normal. It’s when these negative moods persist and eventually manifest into harmful thinking or behavior that depression becomes a psychiatric disorder.

Roughly 16 million Americans suffer from depression, constituting 6.7% of the entire population. Depression is more prevalent in women and is the leading cause of disability in people ages 15-44. Fifty percent of depressed individuals also have an anxiety disorder as well.

Common Sleep Problems Associated with Depression
  • Insomnia
  • Hypersomnia
  • Sleep Apnea

Insomnia affects 75 percent of individuals with depression. Depressed individuals can struggle to fall asleep, stay asleep, and even wake up from sleep (hypersomnia). There has also been research that insinuates a relationship between sleep apnea and depression. In fact, individuals with sleep apnea are five times more likely to suffer from depression as well.


Attention Deficit/Hyperactivity Disorder (ADHD)

ADHD is one of the most common mental illnesses among children, affecting approximately eight to ten percent of school-aged children. It is a condition that consists of differences in brain development where attention, self-control, and hyperactivity are controlled.

Common Sleep Problems Associated with ADHD Disorders
  • Insomnia
  • Daytime Sleepiness
  • Sleep Apnea
  • Periodic Limb Movement Disorder (PLMD) and Restless Leg Syndrome

Both the symptoms of ADHD and the medication used to treat it result in fragmented sleep, as well as other sleep disorders. Seventy-five percent of individuals with ADHD suffer from insomnia, believed to be caused by a delayed circadian rhythm. In addition to trouble falling asleep, individuals with ADHD can have trouble staying asleep as well.


A Final Note on Mental Health

It’s important to understand that mental illness is just that—an illness. Just like you get a fever or a sore throat, it’s not something you have control over and it’s not something to be ashamed of! Mental illnesses, like physical illnesses, can be treated. They just might be a little harder to recognize than a pounding headache. If you suffer from a mental illness of any kind, don’t be afraid to seek help. Just as we nurture our bodies back to health, so we can nurture our minds back to health too.


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