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Sleep has an enormous effect on our mental health. A huge fraction of our day is spent sprawled out, eyes shut, and useless to the world. Children and toddlers often revolt against going to sleep, but as they grow older, they always want more.
Sleep is essential to our core functioning.
Even if we know that intuitively, it’s still easy to underestimate sleep’s importance. According to the Center for Disease Control, a third of Americans don’t get enough sleep. A lack of sleep leads to a truckload of bad medical results, like getting sick more often, obesity, and more rapidly aging skin.
There are serious mental health consequences, too. Sleep deprivation has been used as a form of torture because of how profoundly a person can be affected. Even if you’re losing an hour or two each night, the cumulative effect can be destructive.
What Does Sleep Even Do?
Every living thing on this planet goes to sleep. Yes, even plants have their own form of sleep when they stop doing photosynthesis at night.
In humans, there are at least a couple major functions sleep serves. For one, it repairs our bodies from the wear and tear of the day. Blood pressure drops, giving your heart a break, and your pituitary gland sends out growth hormone so the cells can repair themselves.
There’s a lot happening in the brain while you sleep, too. Research has shown that sleep helps solidify memories. Growing up, did you ever hear your teacher tell you to get some sleep before a big test? This practice makes sure that everything you studied stays locked into your brain by the time you sit down and take a test. Storing old memories and making new ones requires good healthy sleep.
For reference, experts agree most people need between seven to nine hours of sleep per night. This varies for each individual, but most people will fall somewhere in this range. Quality matters too, and eight hours of tossing and turning or shallow sleep just won’t cut it.
The Effects of Poor Sleep on Mental Health
Memory Problems
As I mentioned above, sleep helps consolidate memories. Unfortunately, the opposite is true, too: poor sleep can wreak havoc on your ability to form new memories.
Let’s go back to our studying example. Did you ever stay up cramming all night, then wake up and sit down to take a test and wonder where everything you studied went? You probably didn’t get enough sleep to properly “save” it to your brain’s proverbial hard drive.
Prolonged periods without enough sleep leads to further degradation. Insomnia devastates the hippocampus, the brain’s memory center. There are biological reasons that a lack of sleep causes older memories to blur, and short-term memory to falter.
Difficulty Concentrating
Similarly, lacking quality sleep can make a person feel clouded and slower than they might otherwise be. If you’ve ever tossed and turned all night, you know what it’s like to wake up the next day and feel like you can’t focus on reading or watching videos. Even listening to another person becomes a heroic act.
Many people try to cover up this slowness and difficulty focusing with the use of caffeine—I’m guilty as charged—but that’s only a band-aid.
Check out these brain scans to know what I mean. The BBC showed the differences nicely. The MRI on the left shows a healthy, normally operating brain. The scan on the right is that same brain, but sleep-deprived.
Notice how the normal functioning brain on the left lights up with all types of activity. On the other hand, that same brain on the right shows Studies show that the sleep-deprived brain has much less activity. Areas that were lighting up nicely in the first picture are much more inert.
Here’s a bonus round. Look at this scan.
At first, this looks similar to the last scans. Once again, the healthy brain sits on the left. That same brain on the right also shows depressed activity, only this time it’s not because of sleep deprivation. This is the scan of somebody who is drunk.
That’s right, a sleep deprived brain is impaired in ways not too different than if it were doused in alcohol. Parts of the brain that often struggle while intoxicated—cognitive sharpness, memory, and emotional regulation—also sputter for folks who deal with serious insomnia. In rare situations, people with a severe lack of sleep may even hallucinate. Sleep and mental health affect one another.
Worse Decision Making
Your prefrontal cortex sits at the very front of your brain. This structure is maybe the single defining feature of what makes us human. It’s responsible for abstract thought, expressing your personality, controlling impulses, and making decisions.
You saw in the second brain scan the prefrontal cortex misfire without proper sleep. I can’t overstate the consequences here. In a 2020 study, they looked at what happened to perfectly healthy young adults who were subjected to sleep deprivation. Folks who were kept from sleeping more than five hours one night showed somewhat more impulsive, hasty decisions the following day.
It was worse for people who were subjected to sleep deprivation for five nights in a row. These individuals took far more risks and stumbled through reasoning tasks. Having a chronic lack of sleep carries severe and lasting consequences. Some studies have shown that losing sleep for years may even shrink the size of certain structures in the brain that are used for emotion, memory, and abstract thinking.
What advice do people give when you have a big decision to make? “Sleep on it,” they say. It turns out their words have more merit than one might’ve known.
Moodiness
We’ve already seen how sleep deprivation leads to bad decision-making and poor mental sharpness through an inhibited prefrontal cortex. And with an impaired hippocampus, we know people struggle making or keeping memories.
One other part of the brain I want to talk about is the amygdala. Our emotions center. This little almond shaped mass of gray matter is responsible for our feelings.
When sleep deprivation hits this structure, it’s not as if we just stop feeling things altogether. No, the amygdala goes haywire. Sleep deprivation has shown to naturally lead to a depressed mood. You may not even have something that necessarily made you sad, but the biological weight of losing sleep drags you down.
A sleepy person with a misfiring amygdala may also be super irritable. Basic emotions may feel more raw or uncontrollable. Stick that irritability with more impulsive and risky decision-making, and you can see some of the invisible damage sleep deprivation can deliver.
Mental Illness
For decades, research has shown that one of the greater predictors of mental illness is some type of issue around sleep. Chronic sleep problems affect about half of the clients in a typical mental health clinic. That’s compared to less than twenty percent for the general population. Many mental illnesses—like major depressive disorder, generalized anxiety disorder, and post traumatic stress disorder—literally list sleep issues as one of the possible symptoms.
People are more likely to develop a mental illness when they’re losing sleep. Just look at the horrible chimera of psychological symptoms that can wreak havoc on a person’s life. Sleep deprivation is stressful, and there is overwhelming evidence that stress is a key trigger for many mental illnesses. Also, just to be clear, I’ve focused a lot on insomnia in this post, but hypersomnia (that is, too much sleep) can also trigger similar psychological issues as well.
Individuals already living with mental illness are also going to experience worse symptoms when they’re not rested. Managing psychological issues is hard enough on the best of days. A person needs all their resources to truly thrive. Poor sleep is a serious risk factor for those symptoms worsening.
Sleep and Mental Health are Tightly Connected
Losing sleep is a biological problem. The brain, like other parts of the body, misfires without having rejuvenating rest. The prefrontal cortex fades, leading to foggy thinking and worse decision-making. The hippocampus sputters, distorting a person’s memory. And the amygdala shuts down, leading to irritability and depressed moods.
With pressing responsibilities to tend to and never-ending entertainment at your fingertips, it’s hard to find enough time to keep up with everything. Sleep is often the cut people make to get to everything else. While that’s sometimes unavoidable, I hope this article demonstrates how important it is to prioritize rest whenever you can.
Don’t think of sleep as a time sink, but an investment. Pushing forward while you’re exhausted will make you miserable and put out worse work. On the other hand, getting good sleep will be an essential resource to staying productive and enjoying your life.
There are a number of treatments available for improving your sleep. This site will also continuously be updated with helpful information about sleep hygiene.
If you’re interested in tracking your own sleep, I have a free worksheet you can use when you sign up to my email list. This tool will help track your sleep and mood over the course of a week so you can see what’s working and what needs to change.
Did any of these side effects surprise you? What have you noticed about yourself when you’re sleep deprived? Sound off in the comments below. And if you found this article helpful, or you think it might be of use to someone else, please consider sharing.
