Nightmare disorder is a pattern of repeated frightening and vivid dreams that cause significant distress or impaired functioning. A sleep disorder characterized by repeated occurrences of extended, well-remembered, dysphoric dreams, often involving themes of threat, that result in awakening from sleep and significant distress and impairment, included in DSM-IV-TR, DSM-5, and DSM-5-TR.

 It was formerly known as dream anxiety disorder.

Nightmare disorder

A sleep disorder characterized by repeated occurrences of extended, well-remembered, dysphoric dreams, often involving themes of threat, that result in awakening from sleep and significant distress and impairment, included in DSM-IV-TR, DSM-5, and DSM-5-TR. It was formerly known as dream anxiety disorder.  
Nightmare disorder is one type of parasomnias, which are behavioral sleep abnormalities.

 Nightmare disorder — Nightmares that recur with enough frequency and distress to impact nighttime or daytime function may meet criteria for nightmare disorder. The International Classification of Sleep Disorders, Third Edition, Text Revision (ICSD-3-TR), defines nightmare disorder as follows:

●Repeated occurrences of extended, extremely dysphoric, and well-remembered dreams that usually involve threats to survival, security, or physical integrity; on awakening from the dysphoric dreams, the person rapidly becomes oriented and alert, AND

●The dream experience or sleep disturbance produced by awakening from it causes clinically significant distress or impairment in social, occupational, or other important areas of functioning as indicated by the report of at least one of the following:

•Mood disturbance (eg, persistence of nightmare affect, anxiety, dysphoria)

•Sleep resistance (eg, bedtime anxiety, fear of sleep or subsequent nightmares)

•Negative impact on caregiver or family functioning (eg, nighttime disruption), behavioral problems (eg, bedtime avoidance, fear of the dark), daytime sleepiness, fatigue or low energy, impaired occupational or educational function, or impaired interpersonal or social function.

The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) definition is similar to the ICSD-3-TR definition but adds modifiers for duration and severity as well as two additional specifications: that the nighttime symptoms are not attributable to the physiological effects of a substance (eg, a drug of abuse or medication) and that coexisting mental and medical disorders do not adequately explain the predominant complaint of dysphoric dreams.

DSM-5 diagnostic criteria for nightmare disorder are as follows:

●A. Repeated occurrences of extended, extremely dysphoric, and well-remembered dreams that usually involve efforts to avoid threats to survival, security, or physical integrity and that generally occur during the second half of the major sleep episode

●B. On awakening from the dysphoric dreams, the individual rapidly becomes oriented and alert.

●C. The sleep disturbance causes clinically significant distress or impairment in social, occupational, or other important areas of functioning.

●D. The nightmare symptoms are not attributable to the physiological effects of a substance (eg, a drug of abuse, a medication).

●E. Coexisting mental and medical disorders do not adequately explain the predominant complaint of dysphoric dreams.

Specifiers:

●During sleep onset

●With associated non-sleep disorder, including substance use disorders

●With associated other medical condition

●With associated other sleep disorder

●Acute – Duration of period of nightmares is ≤1 month

●Subacute – Duration of period of nightmares >1 month, <6 months

●Persistent/Chronic – Duration of period of nightmares is ≥6 months

Current severity by the frequency with which the nightmares occur:

●Mild – Less than one episode per week on average.

●Moderate – One or more episodes per week but less than nightly.

●Severe – Episodes nightly.

from Nightmare Disorder link 

Nightmares typically occur during the second half of your sleep period during REM (rapid eye movement) sleep. With nightmare disorder, you remember them upon awakening (unlike sleep terrors).

This condition can significantly disrupt your sleep and affect your quality of life. It can also make underlying mental health conditions, such as depression or anxiety, worse.

Nightmare disorder link  

Nightmare disorder can affect anyone, including children and adults.

It’s more likely to affect people who have any of the following conditions:

• REM behavior disorder (RBD).
• Narcolepsy.
• Sleep apnea.
• Periodic limb movement disorder (PLMD).
• Post-traumatic stress disorder (PTSD).
• Generalized anxiety disorder.
• Social anxiety disorder.
• Depression.

Nightmare disorder occurs in people who have social anxiety disorder or generalized anxiety disorder at approximately three times the rate of the general population. It affects 50% to 90% of people with PTSD.

Approximately 2% to 8% of the general U.S. population has nightmare disorder.

The main symptom of nightmare disorder is a pattern of nightmares. While it’s common to have nightmares every once in a while, if you have them frequently and they interfere with your daily functioning, you may have nightmare disorder.

Common themes of nightmares include threats to your:

• Survival
• Physical well-being.
• Security.

You may also experience the following physical symptoms when you have a nightmare:

• Sweating.
• Shortness of breath.
• Racing heart.

The main emotion nightmares cause is fear, although you may experience other emotions such as:

• Anger
• Anxiety.
• Embarrassment.
• Disgust.
• Shame.
• Sadness.

These physical symptoms and emotions can occur during the dreaming episode, upon awakening from the nightmare or when later remembering the dream.

Due to nightmare disorder, you may have:

• Mood disturbance, such as anxiety or depression.
• Sleep resistance.
• Fatigue.
• Daytime sleepiness (hypersomnia).
• Difficulty concentrating.
• Behavioral issues.
• Impaired functioning at work or school.
• Impaired social functioning.

Quality sleep is very important to your overall health, so it’s important to talk to your healthcare provider if you think you have nightmare disorder.

Researchers continue to study sleep and its effect on us. While they’ve learned a lot about sleep, dreams and nightmares, there’s still much that’s unknown.

Researchers don’t know what exactly causes nightmares and nightmare disorder, but they have multiple theories.

One theory is that nightmare disorder may be influenced by increased hyperarousal that builds during the day and remains at night. Hyperarousal is a mood-altering symptom in which you’re consistently irritable, angry and paranoid. It’s a well-known symptom of PTSD and insomnia. Hyperarousal may make certain areas of your brain overactive while you sleep, causing nightmares.

Another theory involves a concept called fear extinction. Under regular circumstances, your brain is able to combine fearful memories with new and unrelated contexts to allow for normal sleep and dreams. This is called fear extinction. According to the impaired fear extinction theory, people with nightmare disorder continue to activate fear memories during sleep. The theory states that people who have difficulty regulating their emotions in stressful situations and tend to react negatively to stress are more prone to nightmares.

There’s no medical test that can diagnose nightmare disorder. Instead, healthcare providers rely on a thorough history of your nightmares and other symptoms to diagnose nightmare disorder. They will also ask questions about your medical, social, medication, and mental health history.