October 30, 2023 4 min read

The spooky season is finally here. That means we’ll be seeing frightening decorations and terrifying costumes taking over in preparation for Halloween. With the focus now being on all things scary and gory, this is a great time to talk about something nearly everyone has experienced at some point in their life: nightmares.

While occasional nightmares are relatively normal, nightmares can also be a problem. Recurrent nightmares, which are more common among children, plague 3.5-8.3% of adults [1]. Nightmares can impact your waking life and even indicate an underlying sleep disorder. Here’s everything to know about nightmares. 

What Are Nightmares?

Nightmares are disturbing dreams that often awaken the dreamer from sleep. They’re realistically vivid and quite upsetting, with those experiencing them waking up in fear, with a racing heart, and profusely sweating. People experiencing a nightmare are also aware of what is happening once they are woken up.


Most nightmares occur during the rapid eye movement (REM) phase of sleep, which is associated with dreaming. Because more time is spent in REM sleep in the second half of the night, this is also when people usually experience nightmares. 


Nightmares are different from bad dreams in that bad dreams don’t usually wake the dreamer. They are also often confused with night terrors; however, the latter occurs during non-rapid eye movement (NREM) sleep and those affected aren’t aware during or after an episode.


The subject of nightmares varies from person to person, but there are also common themes. A study of dream reports published in the journal Sleep examined over 250 nightmares and 431 bad dreams [2]. The most commonly reported themes were being attacked (48%), interpersonal conflicts (21%), failure or helplessness (16%), being chased (11%), and health problems and death (9%).

What Is Nightmare Disorder?

While most people experience nightmares from time to time, having recurrent nightmares for months, years, or decades even is a sign of ND. Nightmare disorder (ND) is defined as a sleep disorder. More specifically, it is a type of parasomnia in which recurrent nightmares interfere with daily functioning and well-being. 


Like many sleep disorders, ND can be mild to severe and can be short-term or chronic. It most commonly occurs in people with certain psychiatric illnesses. Only about 2-5% of the general population are affected but up to 30% of psychiatric outpatients have ND [3].

Symptoms of Nightmares and Nightmare Disorder

Nightmares differ from bad dreams by their tendency to wake the dreamer. Other features of your typical nightmare are: 


  • Occurring during the second half of the night when we spend the most time in REM sleep. 

  • The dream content is typically vivid, realistic, and upsetting, becoming more disturbing as the dream unfolds. 

  • Usual themes seen in nightmares are threats to safety and survival, helplessness, and conflict.  

  • The dream content evokes strong and negative emotions like fear, anxiety, sadness, anger, and guilt. 

  • The dream is able to think clearly and remember details of the dream immediately upon awakening. 

  • Often, it can be hard to fall back asleep following a nightmare.

The fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5-TR) defines nightmare disorder as ”repeated awakenings with recollection of terrifying dreams, usually involving threats to survival, safety or physical integrity [4].” The only difference between typical nightmares and ND is recurrence and its effects on daily functioning and well-being. 

What Causes Nightmares?

Researchers believe that nightmares and ND are a result of increased hyperarousal paired with impaired fear extinction [1]. 


Explained differently, you’re more likely to have a nightmare if you’re stressed and your brain is unable to cope with this stress. That also explains why certain stress-related psychiatric disorders show a propensity towards nightmares. Examples are post-traumatic stress disorder PTSD and anxiety. Childhood trauma, maladaptive beliefs, and certain traits can all make one prone to nightmares and ND.


However, nightmares can also be a side effect of certain medications (notably antidepressants), drug withdrawal, metabolic problems, and sleep-disordered breathing. Sleep-disordered breathing includes snoring and sleep apnea, which can cause serious sleep fragmentation and low blood oxygen levels. Both can lead to hyperarousal, which makes nightmares more likely [1].

Health Consequences of Nightmares

Having nightmares occasionally isn’t usually a cause for concern. However, if you suffer from recurrent nightmares and they’re interfering with your ability to function normally, then it is a good idea to speak to your doctor.

Recurrent nightmares often signal ND. Many cases of ND are due to an underlying mental health problem, like anxiety, depression, and PTSD. What’s particularly alarming is that recurrent nightmares were found to increase the risk of repeated suicide attempts irrespective of other circumstances in a person’s life [1].


Frequent nightmares can also lead to fragmented sleep, especially if they happen several times at night. If a symptom of sleep apnea, nightmares could signal that your brain and body are not getting enough oxygen during sleep. Fragmented sleep and low blood oxygen increase your risk of high blood pressure, heart disease, and even type 2 diabetes. 

How Are Nightmares Treated?

Treatment for recurring nightmares, of course, depends on what’s causing them. 


Nightmares that are a result of medication can be treated by changing the dosage or prescription. Nightmares due to sleep apnea lessen once this sleep-related breathing disorder is effectively managed with CPAP therapy [5]. Mild cases of sleep apnea or simple snoring can be treated with weight loss, surgery, or  oral appliances.


If due to a comorbid mental health condition, nightmares can be treated with medication, cognitive-behavioral therapy, and exposure therapy, among many other treatments. 


  1. References:
    Gieselmann A, Ait Aoudia M, Carr M, et al. Aetiology and treatment of nightmare disorder: State of the art and future perspectives.J Sleep Res. 2019;28(4):e12820.doi:10.1111/jsr.12820

  1. Robert G, Zadra A. Thematic and content analysis of idiopathic nightmares and bad dreams.Sleep. 2014;37(2):409-417. Published 2014 Feb 1.doi:10.5665/sleep.3426

  1. Dietch JR, Taylor DJ, Pruiksma K, et al. The Nightmare Disorder Index: development and initial validation in a sample of nurses.Sleep. 2021;44(5):zsaa254.doi:10.1093/sleep/zsaa254

  1. Neuspiel DR. Nightmare Disorder. September 2023.https://emedicine.medscape.com/article/914428-overview?form=fpf

  1. BaHammam AS, Almeneessier AS. Dreams and Nightmares in Patients With Obstructive Sleep Apnea: A Review.Front Neurol. 2019;10:1127. Published 2019 Oct 22.doi:10.3389/fneur.2019.01127



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