Nightmares: causes, meaning and how to stop them

What counts as a nightmare?

A nightmare is a long, frightening dream that wakes you up, usually with a clear memory of what happened. Fear is the most common feeling, but anger, disgust, shame or grief can take its place. Nightmares mostly arise during REM sleep, whose periods grow longer toward morning. That is why the worst dreams often come in the early hours.

The scenarios are familiar: being chased, an intruder, someone you love in danger, a fall, a disaster you cannot stop.

They are very common. The American Academy of Sleep Medicine (AASM) estimates that 50 to 85% of adults have an occasional nightmare, and that 2 to 8% have nightmares that cause sleep problems. When nightmares are frequent, distressing and spill over into the day, doctors speak of nightmare disorder. Children have them more often than adults, especially between the ages of 3 and 6.

A nightmare is not a night terror. Night terrors arise from deep non-REM sleep, often early in the night: the person may scream or thrash, seems awake without being so, and usually remembers little or nothing. After a nightmare, you are fully awake and you remember.

What makes nightmares more likely?

Usually several factors add up. Rather than guessing the cause from the dream itself, look at what changed in your days and nights.

Do nightmares mean something?

Not in the sense of a coded message or a warning. A nightmare does not predict anything, and the same image can mean very different things to different people. What it often does reflect is an emotion that is already there: worry, guilt, helplessness, grief. Dreams draw on recent emotional experience, but no one can reconstruct exactly why a given scene appeared on a given night.

The feeling usually tells you more than the setting. Being chased, falling, facing death, meeting a snake or a spider: the symbol pages suggest possible readings, but your own associations count more than any dictionary.

A rehearsal of danger?

According to the threat simulation theory of Finnish researcher Antti Revonsuo, dreaming may partly serve to rehearse threatening situations in a safe setting. The theory is debated, but it helps explain why unpleasant dreams are so common.

What is worth noting

A recurring theme does not hide a message, but it can show when your sleep suffers. Ask yourself: what happened the day before? What did I feel on waking? Did the nightmare come after a short night, a drink, a tense evening?

Nightmares are not a punishment, and a single dream is not a diagnosis.

Which kind of nightmare is it?

Stress nightmares

The most common kind. You are late, unprepared, lost or exposed in front of others. These nightmares tend to fade when the pressure eases.

Trauma nightmares

They replay the event, or its emotion, almost unchanged, and can occur earlier in the night than other nightmares. They are a core symptom of PTSD. Effective treatments exist, and they work best with a professional.

Recurring nightmares

The same scene, night after night. Repetition does not mean the dream will go on until you "solve" a hidden problem. Some clinicians see it partly as a learned pattern, which is exactly what imagery rehearsal tries to change. The guide to recurring dreams goes further.

Nightmares about death or loss

Dreams of dying, of a disaster or of losing someone close are frightening but do not predict anything. They often appear during times of change, of illness around you or of grief.

How to stop nightmares, or at least have fewer

No method guarantees a night without bad dreams. The steps below are the ones with the best support, starting with the most studied.

1. Imagery rehearsal therapy (IRT)

It is the treatment recommended by the AASM for nightmare disorder and for nightmares linked to PTSD. The idea: you change the script while awake, so your brain has another version to play.

• Choose one recurring nightmare, ideally not the most painful one to begin with.
• Write a new version. Change whatever you like: the ending, the place, one detail. It does not have to be happy, only less frightening.
• Rehearse the new version in your mind for a few minutes a day, while awake and calm. Do not replay the original nightmare.
• Keep it up for a few weeks and note how often the nightmare returns.

In a study cited by the AASM's 2010 best practice guide, people trained in IRT went from about seven nightmares a month to two, three months later. If the nightmare is tied to a trauma, practice it with a therapist rather than alone.

A nightmare journal example

Fictional example: it shows how to note a nightmare and the new version you rehearse.

• Dream: "I was driving at night and the brakes stopped working. The car kept speeding toward a wall."
• Emotion: "Panic, then helplessness. Awake at 4 a.m., unable to get back to sleep."
• Recent context: "Three deadlines this week, and a short night on Sunday."
• New version to rehearse: "The car slows down on its own and stops on the shoulder. I get out; the air is cool."
• Question to keep: "Does the nightmare come back after short nights, or only before deadlines?"

One entry proves nothing. Noted over several weeks, these few lines show whether the nightmare is becoming rarer and what tends to come with it.

2. Keep your sleep steady

• Go to bed and get up at regular times, weekends included
• Put screens away in the last hour before bed
• Keep the bedroom cool, dark and quiet
• Limit alcohol and caffeine, especially in the evening
• Avoid a heavy meal just before bed

3. Lower the evening pressure

• A few minutes of slow breathing or a short meditation before bed
• Regular exercise, but not right before bedtime
• Write tomorrow's worries on paper before turning off the light
• Progressive muscle relaxation, one muscle group at a time
• Swap the thriller or the news feed for something calmer in the last hour; it will not program your dreams, but it can make falling asleep easier

4. Lucid dreaming, as an option

Some people learn to recognize that they are dreaming and change the scene from inside. The AASM lists lucid dreaming therapy among the options that may be used for nightmare disorder, with weaker evidence than IRT. It does not work for everyone; stop if practicing it disturbs your sleep. The beginner's guide to lucid dreaming explains how to start.

5. Keep a dream journal

Noting your nightmares, even in three lines, shows how often they happen, what comes with them and whether what you are trying is working. Write only as much as feels manageable.

When to see a doctor

Occasional nightmares are not a cause for concern. Talk to a doctor if:

• they happen several times a week or keep increasing
• they regularly break up your sleep
• you start dreading bedtime
• they began after a trauma, or replay it
• tiredness, mood or concentration suffer during the day
• they started with a new medicine
• self-help has not helped after a few weeks

Depending on the cause, a doctor or sleep specialist may suggest imagery rehearsal therapy, cognitive behavioral therapy (including CBT for insomnia when sleep itself has become difficult), trauma-focused therapy such as EMDR, or, in some cases, medication. For a child with frequent nightmares, start with the pediatrician.