Nightmares: Causes, Nightmare Disorder and Treatment

Nightmares are vivid, disturbing dreams that wake the sleeper and leave a clear memory of the dream along with lingering fear, anxiety or distress. They arise mostly during REM (rapid eye movement) sleep, so they cluster in the second half of the night, when REM periods are longest. Occasional nightmares are a normal part of human sleep; when they are frequent and distressing enough to disrupt sleep or daytime life, clinicians may diagnose nightmare disorder, a sleep condition with well-studied psychological treatments.

This page explains what happens in the brain during nightmares, how they differ from night terrors, what makes them more likely, how they relate to trauma and PTSD, and what the research says about treatment. It is educational information, not a substitute for an assessment by a doctor or sleep specialist.

What Nightmares Are

During REM sleep the brain is highly active, the body's major muscles are temporarily paralyzed, and dreams tend to be long, story-like and emotional. Brain-imaging research shows that emotional areas such as the amygdala are especially active in REM, while parts of the prefrontal cortex involved in reflection and reality-checking are relatively quiet. That combination helps explain why dreams can feel intensely real and why we rarely question their logic until we wake.

A nightmare is a REM dream in which the emotional tone becomes strong enough to end sleep. Fear is the most common emotion, but nightmares can also be dominated by helplessness, anger, sadness, guilt or disgust. Typical themes include being chased, attacked or trapped, falling, failing at something important, and harm coming to loved ones.

Sleep researchers often distinguish nightmares, which wake the dreamer, from bad dreams, which are unpleasant but do not. Dream-diary studies suggest bad dreams are more frequent than true nightmares. Both appear to draw on waking concerns: people under stress tend to dream about versions of those stresses, often in exaggerated or symbolic form.

Why do we have nightmares at all?

There is no settled answer. One influential idea is that dreaming helps process emotional memories, and that nightmares occur when that process is overwhelmed. Levin and Nielsen's (2007) neurocognitive model proposes that dreaming normally helps extinguish fear memories by recombining them in new, safer contexts; nightmares may reflect a breakdown in this function, especially when a person is already highly distressed. Other researchers, such as Antti Revonsuo, have suggested that threatening dreams evolved as a form of rehearsal for responding to danger. These theories are still debated and difficult to test directly.

Nightmares vs. Night Terrors

Nightmares and night terrors (also called sleep terrors) are often confused, but they are different events that arise from different stages of sleep.

Night terrors are classed as a disorder of arousal from non-REM sleep, in the same family as sleepwalking. A child having one may seem awake but cannot be reasoned with, and usually has no memory of it the next morning. Nightmares, by contrast, are remembered all too well. A third experience, sleep paralysis, involves waking during REM while the body is still paralyzed, sometimes with frightening dream-like hallucinations.

Causes

Most nightmares have no single cause. They become more likely when several factors pile up, such as stress plus poor sleep plus alcohol.

Psychological factors

Stress is the most consistent predictor of nightmare frequency in everyday life. Exams, conflict, money worries, grief and big transitions are all linked to more disturbing dreams. Nightmares are also more common in people with depression, anxiety disorders and especially trauma-related conditions. Personality research has found that people high in emotional sensitivity or neuroticism tend to report more nightmares and to find them more distressing.

Sleep-related factors

Short or irregular sleep can produce "REM rebound", in which the brain makes up lost REM sleep with longer, more intense REM periods, and dreams can become more vivid. Other sleep disorders, including insomnia and obstructive sleep apnea, fragment sleep and increase the number of awakenings, which makes it more likely that dreams are remembered.

Alcohol, substances and medications

Alcohol suppresses REM sleep early in the night; as it wears off, REM can rebound in the early morning hours, often with intense dreams. Withdrawal from alcohol or sedatives can also bring on vivid nightmares. A number of prescription medications list vivid dreams or nightmares as possible side effects, including some medications that act on blood pressure, mood or sleep. Anyone who suspects a medication is affecting their sleep should raise it with the prescriber rather than stopping or changing it on their own.

Physical health factors

Fever is a well-known trigger of vivid, disturbing dreams, especially in children. Pain, breathing problems during sleep and other medical conditions that disrupt sleep may also contribute. This is one reason a doctor will usually ask about general health and other sleep symptoms when someone reports frequent nightmares.

Nightmare Disorder

The DSM-5-TR lists nightmare disorder among the sleep-wake disorders, and the International Classification of Sleep Disorders includes it as a parasomnia. In summary, the DSM-5-TR describes:

• Repeated, extended, extremely unpleasant and well-remembered dreams that usually involve threats to survival, security or physical integrity, generally during the second half of the main sleep period.
• On waking from the dream, the person rapidly becomes oriented and alert.
• The sleep disturbance causes clinically significant distress or impairment in social, work or other important areas of life.
• The nightmares are not better explained by the effects of a substance, and coexisting mental or medical conditions do not adequately explain them.

Clinicians can specify whether the nightmares occur with another mental disorder, medical condition or sleep disorder; how long they have lasted (acute, subacute or persistent); and their severity, which is based on frequency, from less than once a week on average (mild) to nightly (severe). Only a qualified professional can make the diagnosis, and the criteria are a summary for understanding, not a self-test.

The key idea is impact. Many people have occasional nightmares without any disorder. The diagnosis is about nightmares that recur and cause real problems, such as fear of going to sleep, daytime fatigue, low mood or difficulty concentrating.

PTSD Nightmares

Recurrent distressing dreams related to a traumatic event are one of the intrusion symptoms in the DSM-5-TR criteria for post-traumatic stress disorder. Studies of people with PTSD consistently find that a large majority report frequent nightmares, although exact percentages vary widely by sample and by how nightmares are measured.

Trauma-related nightmares differ from everyday ones in several ways:

• They can replay the trauma closely, sometimes almost like a memory, rather than transforming it into symbolic dream content.
• They are not confined to REM sleep. Research has recorded trauma-related awakenings from non-REM sleep as well.
• They can persist for years and often continue even when other PTSD symptoms improve.
• They feed a cycle of avoidance. People may delay bedtime, use alcohol to sleep or avoid sleep altogether, which worsens insomnia and daytime symptoms.

Frequent nightmares in PTSD are associated with greater overall symptom severity and with depression. In some research they have also been associated with a higher risk of suicidal thoughts, which is one reason persistent trauma nightmares deserve professional attention. If you or someone you know is in crisis, see crisis resources for immediate support.

For broader background, see trauma and PTSD and complex PTSD.

Nightmares in Children

Nightmares are common in childhood. They tend to become noticeable in the preschool years, when children's imagination, language and understanding of danger are developing quickly, and they often decrease through later childhood and adolescence. Common triggers include frightening stories or media, changes such as starting school or a new sibling, family conflict, and illness with fever.

Child-development and sleep specialists generally suggest a calm, matter-of-fact response:

• Offer brief comfort and reassurance, acknowledging that the dream felt scary without dwelling on its details.
• Help the child settle back in their own bed where possible, so that waking does not become strongly rewarded.
• Keep a consistent, calming bedtime routine and limit frightening content in the evening.
• For a recurring dream, some families talk about it in the daytime, or have the child draw it and invent a new ending, a child-friendly version of the rescripting used in imagery rehearsal therapy.

Persistent nightmares after a frightening or traumatic experience, nightmares alongside other changes in behavior, or any concern about breathing during sleep are good reasons to talk to a pediatrician. See anxiety in children for related guidance.

Evidence-Based Treatment

Frequent nightmares are not something people simply have to live with. Several approaches have research support, and the choice depends on whether nightmares are linked to trauma, another sleep problem or a medical cause.

Imagery rehearsal therapy (IRT)

Imagery rehearsal therapy is the most widely studied psychological treatment for chronic nightmares, and the American Academy of Sleep Medicine's 2018 position paper recommended it for nightmare disorder and PTSD-associated nightmares. In outline, a clinician helps the person:

1. Choose a recurring nightmare, often starting with a less intense one.
2. Change the dream in any way they like, such as a new ending, a changed setting or a different storyline, without recounting the traumatic content in detail.
3. Write down the new version.
4. Rehearse the new dream mentally for a few minutes each day.

In a randomized trial with sexual assault survivors with PTSD, Krakow and colleagues (2001) found that IRT significantly reduced nightmare frequency and also improved sleep and PTSD symptoms compared with a waitlist. Later studies and meta-analyses have generally supported these findings, though effects vary across groups, and some studies of military veterans have found smaller benefits. IRT is usually delivered over a small number of sessions, and it is often combined with other sleep or trauma treatment.

Exposure, relaxation and rescripting therapy (ERRT)

ERRT, developed in trauma research settings, combines nightmare rescripting with education about sleep, relaxation training and written exposure to the nightmare content. It has shown promising results in trauma-exposed groups, although the evidence base is smaller than for IRT.

CBT for insomnia

Cognitive behavioral therapy for insomnia (CBT-I) targets the poor sleep that often comes with nightmares. Because fragmented sleep and dread of bedtime can keep nightmares going, CBT-I is frequently combined with IRT. For more on psychological approaches to sleep, see sleep disorders and cognitive behavioral therapy.

Trauma-focused therapy

When nightmares are part of PTSD, treating the underlying trauma can reduce them. Approaches such as prolonged exposure, cognitive processing therapy and EMDR have strong evidence for PTSD overall. Nightmares sometimes persist after these treatments, which is why some clinicians add a nightmare-specific intervention.

Medication

Medication is one option a doctor may discuss, particularly for trauma-related nightmares. The research picture is mixed: a medication that showed benefit in early, smaller studies did not outperform placebo in a large 2018 trial with military veterans (Raskind et al.), and guidelines have been revised as evidence accumulates. Decisions about medication belong in a conversation with a prescribing clinician who knows the person's full health history.

Self-Help Strategies

For occasional nightmares that are not linked to trauma, general sleep and stress practices may help. These are wellbeing habits, not treatments for a disorder, and persistent or severe nightmares warrant professional support.

• Keep a regular sleep schedule. Consistent bed and wake times reduce sleep deprivation and REM rebound. See sleep hygiene for the research behind common recommendations.
• Be cautious with alcohol in the evening. Because alcohol disrupts REM sleep and can cause rebound later in the night, cutting back is one of the more evidence-informed changes people can make.
• Wind down before bed. Relaxation practices such as progressive muscle relaxation or slow breathing can make it easier to fall back asleep after waking.
• Notice patterns. A simple diary of nightmares, stress, alcohol and sleep times can reveal triggers and is useful to bring to a doctor.
• Have a plan for waking. Grounding the senses (turning on a soft light, noticing familiar objects, cool water) can help the body settle after a nightmare. See grounding techniques.

Self-guided versions of imagery rehearsal have been studied, and some people use the rescripting idea on their own for ordinary recurring bad dreams. When nightmares relate to trauma, though, working with a trained clinician is advisable, because rehearsing trauma-related content without support can be distressing.

Summary

Nightmares are a normal feature of REM sleep that become more frequent under stress, sleep loss and alcohol, and that are especially common after trauma. When they recur often and affect sleep or daytime life, they may meet the criteria for nightmare disorder. Research supports structured psychological treatments, especially imagery rehearsal therapy, alongside better sleep and treatment of any underlying trauma. Anyone whose nightmares are persistent or distressing can start by talking to a doctor or a mental health professional.