Overview

Nightmares are dreams that have disturbing or upsetting themes that cause us to have negative feelings such as fear or anxiety so much so that it causes us to wake up. Nightmares don’t generally happen often but are common in children, adolescents and in adults usually when under some sort of stress. Nightmare disorder however is a rare condition where nightmares reoccur often, cause extreme distress, disruption to sleep and daily life and fear of going to sleep. It is classed as a type of parasomnia which are sleep disorders that cause abnormal behaviours during sleep.^1,2 Other parasomnias include, sleep terrors, sleepwalking, bedwetting and sleep-related hallucinations.³

There can be several causes of nightmare disorder that also work together and contribute to different aspects of the condition including psychological, neurological and environmental factors which will be explored in this article. Psychological factors include stress, trauma and mental disorders which can affect onset and persistence of nightmares. Neurological factors such as neurotransmitter imbalances and abnormal brain activity play roles in formation of the nightmare. Environmental factors can include medications, substance use or irregular patterns in sleep which can trigger or exacerbate the nightmares.¹ Understanding what causes this condition as well as how these causal pathways may interact is crucial, not only for accurately diagnosing the condition but also for deciding on the most effective and appropriate line of treatment.

Understanding nightmare disorder

Nightmares tend to occur in the second half of your sleep period during rapid eye movement (REM) sleep. They tend to be disruptive enough to wake you from your sleep and can be emotionally disruptive which can affect your quality of life if frequent enough.¹

Nightmare disorder is a serious condition that is recognised as a mental illness and is classified as a DSM-5-TR in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision, which is the diagnostic manual used by mental health professionals worldwide.⁴ Your symptoms are required to hit certain criteria to be classed as a disorder rather than just having nightmares. Nightmare disorder can range in severity depending on their occurrence and can either be:¹

• Mild – nightmares that occur less than once a week
• Moderate – nightmares that occur once or more than once a week
• Severe – nightmares that occur every night

Nightmare disorder can also range in duration and is classified by one of the following:¹

• Acute – nightmare disorder that is ongoing for a month or less than a month
• Subacute – nightmare disorder that lasts for more than a month but less than six months
• Chronic – nightmare disorder that lasts for six months or longer

Nightmare disorder is a rare condition that affects approximately 4% of the world's adult population and 1% of children.⁵ Nightmare disorder can happen to anyone however it is more likely to affect high-risk groups or those with a pre-existing condition such as:¹

• Depression
• Social anxiety disorder – occurs at 3 times the rate in people with this disorder
• Generalised anxiety disorder (GAD) – occurs at 3 times the rate in people with GAD
• Post-traumatic stress disorder (PTSD) – affects 50-90% of those with PTSD
• Periodic limb movement of sleep disorder (PLMSD)
• REM behaviour disorder (RBD)
• Sleep apnea
• Narcolepsy

Symptoms of nightmare disorder

The main symptom of nightmare disorder is the frequency and pattern of nightmares. Nightmares are often vivid, feel real and can include disturbing and unsettling themes such as death, violence and threats to your security, survival, or physical well-being. You can experience both physical and emotional symptoms when you have a nightmare:¹

Physical symptoms you may have include:

• Racing or pounding heartbeat²
• Sweating
• Shortness of breath

Emotional symptoms you may have include:

• Sadness
• Fear
• Anxiety
• Anger
• Disgust
• Embarrassment
• Shame

For it to be classed as a disorder you will also have to experience other symptoms such as:

• Daytime sleepiness (hypersomnia)
• Fatigue or low energy²
• Sleep resistance
• Mood disturbances such as depression, anxiety or bedtime anxiety
• Difficulty concentrating and problems with memory
• Behavioural issues
• Problems with daily functioning such as at school, work, or in social situations²

Causes of nightmare disorder

The exact cause of nightmare disorder is not known but several factors such as psychological, neurological, and environmental factors may trigger or contribute to the condition.

Psychological factors

Stress or anxiety

Stress and anxiety, either chronic or in ordinary stress, or anxiety-inducing situations can influence dream content and trigger nightmares.²

Trauma or PTSD

Post-traumatic nightmares such as after an accident, injury, abuse, or other traumatic events increase the chances of you having nightmares. Replaying traumatic events in your dreams or having symbolic representations in your dreams often occurs.²

Mental health conditions and other disorders

Depression and other mental health disorders such as bipolar disorder and schizophrenia are linked to an increased risk of nightmares. Other medical conditions such as cancer or heart disease can also trigger nightmares.²

Neurological factors

Brain activity - hyperarousal and impaired fear extinction

Hyperarousal is a mood-altering symptom that causes you to be in a heightened state and makes you feel consistently irritable, angry and paranoid often. This can be observed in people with PTSD and anxiety, which builds up during the day and remains at night. It causes certain areas in your brain such as the amygdala to stay in an overactive state whilst you sleep, causing increased emotional intensity in dreams and more vivid nightmares.¹

Fear extinction is where our brains combine and change out fear-inducing memories with new and unrelated contexts and themes to allow for normal dreams. Impaired fear extinction can emerge due to dysregulation in areas of the brain such as the hippocampus, amygdala, and prefrontal cortex. However these areas continue to activate and recall fear memories during sleep, and show decreased rational control over these leading to nightmares.¹

REM sleep dysregulation

Rapid eye movement (REM) sleep is a sleep stage where your eyes move behind your eyelids and is when most dreams and nightmares happen. REM sleep is important for regulating emotions and reconsolidation of memories, particularly bad ones. Abnormalities in REM sleep can lead to more negative thinking and so leads to increased risk in nightmares and increased frequency of nightmares⁶.

Neurotransmitter imbalance

An imbalance in neurotransmitters such as serotonin, dopamine, and noradrenaline is often caused by taking drugs or withdrawing from drugs such as antidepressants and antipsychotics. These are linked to altering dreams, causing nightmares and problems with emotional processing.⁷

Environmental factors

Sleep deprivation and irregular sleep schedules

Changes and disruptions to sleep schedule as well as reduced sleep especially affects those in high-risk groups such as shift workers, students, and insomniacs.²

Substance use

Substance misuse as well as withdrawal such as from alcohol, recreational drugs, caffeine, and nicotine can increase risk of nightmares.²

Medications

Some side effects of medications such as certain antidepressants, beta-blockers, blood pressure medications, SSRIs, SNRIs, anticholinergics, drugs used to treat Parkinson’s disease or to help stop smoking all potentially trigger nightmares.²

Scary movies, books, or video games

Consuming scary or horrifying stimuli such as watching a scary movie, playing a violent video game, or reading a gruesome book especially before you go to sleep can be associated with nightmares and induce some of the themes in the nightmares.²

External stimuli during sleep

External sensory stimuli you experience whilst you are sleeping such as loud noises, bright or flashing lights, too hot or cold or changing temperatures, and unsuitable or uncomfortable sleeping environments can influence dreams and affect dream intensity. For example, sounds of traffic induced more themes related to travelling and streets.⁸

Diet and late-night eating

There is a possible link between eating high-carb or high-fat meals before bed and influencing vivid dreams. Eating late, especially just before sleep, leads to increased metabolism and brain activity during sleep.⁹

Diagnosis, management and treatment of nightmare disorder

Once diagnosed by your doctor based on the criteria of nightmare disorder and your symptoms, there are two main types of treatments that help manage this condition depending on the cause and are often used in combination with each other; therapy and medication.

The main form of therapy advised is psychotherapy, which is a talking therapy of which can include:¹

• Cognitive behavioural therapy (CBT)
• Imagery rehearsal therapy (IRT)
• Exposure, relaxation and rescripting therapy (ERRT)

CBT based therapy involves going through what you remember from your nightmares with a therapist or psychologist and then trying to guide you through reimagining your nightmares with less disturbing outcomes in order to try and “reprogram” them.

IRT and ERRT involve aspects such as tracking sleep/ wake patterns and nightmare frequency and severity with a sleep log. Learning about the nature of your nightmares and what they might mean allow for practising skills that target nightmare-related thoughts and emotions.^1,2

You may also by prescribed with medication alongside of or instead of psychotherapy. There are two types of medications used to treat nightmare disorder:¹

• PTSD associated nightmare disorder medications – such as olanzapine, risperidone and aripiprazole
• Non-PTSD associated nightmare disorder medications, such as triazolam or prazosin

Summary

Nightmare disorder is a complex sleep disorder where nightmares occur frequently and cause extreme distress leading to impact on quality of life. There can be several causes of nightmare disorder, including psychological factors such as stress, anxiety, PTSD and depression that increase both the frequency and themes of nightmares. Neurological factors such as abnormal brain activity and neurotransmitter imbalance which can increase the persistence and vividness of nightmares.Environmental factors such as medications, sleep deprivation, late night eating and sensory stimuli before and during sleep trigger and exacerbate nightmares and the intensity of their themes. There are often multiple overlapping causes for nightmares. Recognising the causes of this disorder is important for the most appropriate treatment which often requires a combination of different types of therapies and medications.