Have you ever fumbled through your day less focused and under a layer of fog after a few nights of poor sleep? That's sleep deprivation. Not only is it hard to get through the day when you don't sleep well, but sleep deprivation can also have significant mental health impacts, from focus to mood.

Let's talk about why sleep is an essential pillar of your mental health and what happens when you don't get enough of it. For more, see how to sleep well with depression, how to banish nighttime anxiety and what the cognitive shuffle method is.

Why is sleep important for the brain? 

Generally, we should all get at least seven hours of sleep each night, but life can get busy, and late nights and early alarms creep in to disrupt sleep. According to the Cleveland Clinic, 70 million Americans struggle with a sleep disorder like insomnia. 

This adds up to more than fatigue. The Centers for Disease Control and Prevention found that sleep deprivation makes you 2.5 times more likely to deal with mental distress. 

How does sleep affect mental health in such a significant way? It all comes down to what your brain does while you rest. (Hint: it's a lot.) As you snooze, your brain:

• Facilitates communication between nerve cells.
  
• Removes toxins.
  
• Processes what you've learned during the day.
  

Without enough sleep, you lose brain plasticity, which means your brain can't adapt to stimuli as it should. This brings us back to the connection between mental health and sleep. When your brain can't solidify memories or learn new things, you don't feel great mentally. 

Six ways sleep deprivation affects mental health

Let's dig into specific ways that the lack of sleep translates into mental health challenges. 

1. Mood swings 

Prolonged sleep deprivation takes a toll on your ability to regulate your emotions. You might have experienced the following scenario: You slept poorly the night before, and the next day, you feel like you could cry or have an angry outburst at a moment's notice.

Studies show that lack of sleep negatively impacts our moods. It can make you more prone to anger and emotionally reactive in general. Those mood changes don't just make you feel off-kilter as you go about your day. They can also impact your decision-making ability. 

A 2017 study found that sleep deprivation makes us more sensitive to stressful stimuli and emotionally aroused. Sleep is integral to our ability to manage our emotions and everyday stressors. 

2. Perception of the world 

When you aren't getting the sleep you need, interacting with the world feels more difficult, because it is. Go too long without sleep and you can even start hallucinating. Sleepless nights directly impact how you perceive what's going on around you. Being sleep-deprived can change how you interpret situations and as a result, how you respond to them. 

Sleep impacts how we see the world, as well. One study showed that getting insufficient sleep can change how we see color. 

3. Coping with stress 

Sleep and stress have an interesting relationship. Being stressed can make it harder to get high-quality sleep, but a lack of sleep can make you more stressed. 

In a recent survey, the American Psychological Association found that 21% of adults reported an uptick in their stress levels when they weren't getting enough sleep. If you're already stressed, the issue compounds. A whopping 45% of people who reported higher stress levels going into the survey said lack of sleep increased their stress even more. 

Many respondents reported other stress-inducing adverse effects of bad sleep, including:

• Sluggishness (53%).
  
• Irritability (38%).
  
• Trouble concentrating (29%).
  
• Lack of motivation (25%).
  

4. Concentration and brain fog 

Sleep deprivation makes it harder for your brain to form memories, stay focused and learn new things. That tired feeling that comes with a lack of good sleep often translates to brain fog that can interrupt your day. 

In fact, if you've been struggling with concentration, check your sleep habits. Research shows that sleep deprivation can make your reaction times longer and make it harder for you to pay attention. 

Lack of sleep is also associated with attention-deficit/hyperactivity disorder. The relationship between ADHD and sleep is pretty complex and bidirectional: People with ADHD may experience disordered sleep, and those who struggle to get quality sleep may experience ADHD symptoms. 

5. Hormone disruption 

As we mentioned before, sleep doesn't necessarily mean your body and brain power down. In fact, your system uses the time you're asleep to do some critical work. That includes some key hormonal processes. 

Specifically, all of these hormones go to work while you sleep:

• Growth hormones.
  
• Melatonin (controls your sleep-wake cycle).
  
• Thyroid-stimulating hormone.
  
• Cortisol (a stress hormone).
  
• The hormones that affect your appetite.
  

Since your hormones control a wide range of things in your body — many of which directly impact how you feel — this matters for both your mental and physical wellness.

The flip side of this is also true. A hormone imbalance can cause sleep issues, a problem that's particularly common in women going through menopause. If you've been dealing with persistent insomnia, talk to your doctor. In some cases, correcting a hormonal imbalance unlocks consistent, high-quality sleep. 

6. Contribute to and amplify mental illness 

There's a clear connection between the lack of sleep and mental health, but if you already have a mental illness -- or even dealing with some of the symptoms of one -- sleep becomes extra important. 

Why? Let's look at the cyclical relationship between sleep and a few specific mental illnesses: 

• Anxiety: You can't get rid of anxiety by sleeping enough, but rest certainly matters. Sleeplessness can trigger anxiety symptoms. In turn, anxiety can make it harder to fall asleep. 
  
• Depression: Sleep disturbances are a hallmark symptom of major depressive disorder, while insomnia can heighten your risk for depression. 
  
• Seasonal affective disorder: SAD makes most people experience depressive symptoms in the winter (although some experience it during other seasons). When medical professionals diagnose a person with SAD, they check for sleep problems because they're a primary symptom. 
  
• Bipolar disorder: This condition can wreak havoc on your sleep cycles, whether you have a manic or depressive episode. That's particularly bad because sleep disturbances can make your symptoms worse. 
  
• Borderline personality disorder: Working on your sleep becomes extra important when you have BPD, because this condition makes you more likely to have sleep problems, but sleep deprivation also worsens your symptoms.
  

If you're dealing with persistent sleep problems paired with the symptoms of a mental health condition, talk to a professional.