Sleep Disorders

There are five sleep disorders you need to know for AP Psychology.  They are insomnia, narcolepsy, REM sleep behavior disorder (RBD), sleep apnea, and somnambulism.  We'll explore each one, along with common treatments.  

This article assumes that you are familiar with different phases of sleep.  If you need a quick refreshers, I've got you covered. ​

Insomnia is characterized by difficulty falling asleep or staying asleep.  Sometimes, this means a person cannot fall asleep when they want to.  It may also mean that a person wakes up at night and is unable to go back to sleep.  Other people wake up to early, and then cannot go back to sleep before they need to start their day.

One area where students struggle is distinguishing what makes something a disorder.  It's common for people to occasionally experience trouble sleeping.  For example, you may be startled awake by an unsettling dream, and then be unable to fall back asleep.  This is frustrating, but by itself does not constitute a disorder.

Insomnia occurs when a person has difficulty sleeping for a period of several weeks or months.  This prolonged shortage of sleep has a number of negative consequences on physical and mental health.  In contrast, missing single night of sleep is frustrating and not ideal, but the consequences are less severe.

Insomnia is a very common sleep disorder.  A recent meta-analysis estimated that over 16 percent of the global population has insomnia.  This would mean that approximately 850 million people were living with insomnia when the study was conducted in 2025.​

Narcolepsy is a disorder where people can't prevent themselves from falling asleep during the day.  Narcolepsy can also result in being unable to control one's muscles and having vivid hallucinations.

Like before, it's important to distinguish this from a more banal and common experience.  It is easier to fall asleep when you are tired, and normal to suddenly fall asleep if you are very tired.  

Narcolepsy is different from falling asleep due to normal fatigue.  First, the symptoms of narcolepsy are often worse when a person has a strong emotional reaction, like fear or excitement.  Most people don't fall asleep or lose control of their muscles when they are stressed or excited.  Second, people with narcolepsy often rapidly enter REM-like sleep.  This includes can include muscle paralysis and vivid, dream-like hallucinations.  This is different from typical sleep where REM sleep is preceded by a long period of non-REM sleep.​

REM sleep behavior disorder is also known as RBD.  It affects people during REM sleep.  When most people enter REM sleep, their muscles are paralyzed.  They also experience hallucinations that we call dreams.

A person with REM sleep behavior disorder has dreams during REM sleep, but their muscles are not paralyzed.  In addition, their dreams are often frightening and realistic.  They often report feeling attacked or threatened while sleeping.  As a result, a person with RBD may try to flee a threat.  They may also lash out by hitting or kicking.  Violent actions are uncommon, but injuries are not.  For example, people with RBD often fall out of bed.

RBD is uncommon.  A recent study estimated that about 1-2 percent of the population may have RBD.​

People with sleep apnea briefly, but repeatedly, stop breathing while they sleep.  These episodes only last a few seconds, so many people are completely unaware that they have sleep apnea.  However, the interruptions to normal breathing are long enough to significantly disrupt a person's sleep.  Sleep apnea can be caused by a partially blocked airway or abnormal brain activity.

Sleep apnea is very common.  A recent review found that about 26 percent of adults in the United States had obstructive sleep apnea.  The same researchers noted that sleep apnea increases the likelihood of heart attacks, vehicle accidents, and workplace injuries.​

Somnambulism is the medical term for "sleep walking."  People with somnambulism will walk around while they are asleep.  They may also do other complex behaviors while they are awake.  This can be dangerous.  For example, a person with somnambulism may leave the house during dangerous weather.  They may also get into a car and start driving.

Like with REM sleep behavior disorder, people with somnambulism are unaware and unable to control their actions while asleep.  Unlike RBD, somnambulism typically occurs during NREM sleep.  As a result, somnambulism also doesn't feature scary dreams.  Most people with somnambulism do not appear distressed.

Somnambulism is most common in childhood.  Most children will grow out of it without outside intervention.  ​

How does all of this relate to the chapter?  That's a great question.  Let's dive in.

Many of these disorders are caused by a malfunction in a normal sleep process.  For example, REM sleep behavior disorder occurs when muscles don't become paralyzed as is typical in REM sleep.  Understanding how typical sleep works is fundamental to understanding where things go wrong.  More on that later.

(If you need a quick refresher on sleep, click here!)

Sleep disorders are also related to other biological processes.  Most notably, brain activity, neurotransmitters, and hormones.  When these processes do not function in typical ways, abnormal sleep may be the result.  Psychoactive drugs alter how neurotransmitters behave in the brain.  This can counter negative affects of atypical brain activity.​

Let's also consider how the science principles in AP Psychology relate to sleep disorders.

First, studying sleep has some specific challenges.

Some of the methods we use to study the brain do not work well when trying to study sleep.  This may sound obvious, but if a person cannot sleep, you can't study them sleeping.  MRI's are very loud, and it's hard to sleep in one.  For that reason, scientists often use EEGs to study sleep.  An EEG uses a net of sensors that can be worn like a cap.  This is significantly less less likely to disrupt sleep.  (Side note: If you'd like to see cats in crocheted EEG caps, here you go.  You're welcome.)  It's good to have something, of course, but EEG readings are more limited than more modern tests.

Sleep studies require patients to come into labs and sleep there.  This may also be necessary to diagnose a sleep disorder.  There are some important considerations when conducting these studies.  First, sleeping in a strange place is challenging for many people.  This can alter the outcome of these studies.  From an ethical point of view, people who are asleep are more vulnerable than those who are awake.  Scientists who study sleep must take appropriate steps to prevent people from being harmed while they are unconscious.   New technology is making it easier to conduct sleep studies outside of the lab, but it's not always a perfect substitute.

Finally, psychology experiments are challenging because it's difficult to isolate and define variables.  Psychoactive drug testing is one of the places where this is less of a problem.  Drug studies typically use all of the classic strategies to eliminate bias and confounding variables.  For example, they typically use placebos, control groups, and double-blind all participants.  These methods allow researchers to determine that drugs are effective and safe before they are used to treat sleep disorders.​

We learn about these disorders in isolation.  Meaning, we're interested in knowing what they are and how they are treated.  The real world is messier.  By definition, a disorder affects multiple areas of a person's life and well being.  Often, they are linked with other struggles.

Sleep disorders are often co-occur with the mental health conditions described in Unit 5.  A recent study found that over 50 percent of people diagnosed with sleep apnea had "some degree of anxiety." 

As always, it's harder to determine causation than it is association between variables.  Sometimes, stress and anxiety interrupt sleep.  Anxious thoughts, worries, and ruminations may prevent people from relaxing enough to fall sleep.  Alternatively, developing a sleep disorder may lead to mental health conditions.  A person with narcolepsy may be very anxious that they will be embarrassed if they fall asleep in public.  Finally, psychological disorders and sleep disorders sometimes share a single cause.  Grief can interrupt sleep, but it can also create feelings of intense worry and sadness.  In class, we have to divide all of this up in some logical way, but real world interactions are complex.

There's also overlap between the treatments for sleep disorders and the the treatment of mental health conditions.  These treatments are covered in more detail in Unit 5.  For example, cognitive behavior therapy (CBT) can be effective in treating a wide range of mental health conditions and sleep disorders.  This article describes how CBT can be used to help patients with insomnia.  CBT therapists help clients develop new habits and ways of thinking.  Common lifestyle changes can also positively impact mental health and sleep quality.  A person who commits to exercising more often may find that they are less anxious and sleep better.

Similarly, psychological disorders and sleep disorders may be treated with psychoactive drugs.  This route of treatment emphasizes the importance of neurotransmitters, which influence all of our thoughts and behaviors.  Unfortunately, many psychoactive drugs have side affects that affect mood, energy, and sleep.

Sleep disorders also relate to human development, as covered in Unit 3.  For example, somnambulism is most common in childhood.  Yet, most people will stop sleepwalking as they age.  They naturally grow out of it.  This is true of many other behaviors, like pretend play, that we observe in children.  Second, sleep difficulties may also be related to cognitive decline during aging.  For example, RBD is strongly linked to later development of Parkinson's disease.

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