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Nightmares: Causes, Nightmare Disorder, and How to Stop Them

Most nightmares are normal and occasional, but frequent, distressing ones can become nightmare disorder. Here's what causes nightmares, what the research says about imagery rehearsal therapy, and when to get help.

Almost everyone has a bad dream now and then, and for most people that’s simply a normal, if unpleasant, part of sleep. Nightmares become a bigger concern — sometimes described as nightmare disorder — when they happen often, cause significant distress, or start interfering with sleep and daily life, at which point evidence-backed approaches like imagery rehearsal therapy (IRT) can help.

What’s the difference between occasional nightmares and nightmare disorder?

Occasional nightmares are the ones most people have a few times a year after stress, a scary movie, or an odd meal — unpleasant, but not a sign anything is wrong. Nightmare disorder, by contrast, is a recognized sleep condition where frequent, vivid, distressing dreams repeatedly wake the sleeper and lead to real daytime consequences: anxiety about going to bed, fatigue, trouble concentrating, or avoidance of sleep altogether. Nielsen and Levin (2007) describe nightmares on a spectrum, from harmless and rare to frequent and clinically significant, noting that what matters most is the degree of distress and disruption, not just how scary the content is. If nightmares are happening most nights or clearly affecting your functioning, that’s a different situation from an occasional bad dream, and it’s worth mentioning to a doctor or sleep specialist rather than trying to self-diagnose.

What causes nightmares?

Nightmares seem to arise from a mix of stress, sleep disruption, and how the brain processes emotional memory during REM sleep, though researchers haven’t landed on one single cause. In a large population study, Sandman and colleagues (2013) found that nightmares were more common among people reporting poor sleep quality, insomnia symptoms, and higher psychological distress, suggesting a close two-way relationship between mental strain and disturbing dreams. Common contributors people report include:

Because nightmares happen mostly during REM sleep, it can help to understand how that stage differs from deeper, non-REM sleep — see REM vs NREM Dreams: Two Different Machines for more on why REM dreams tend to be more narrative and emotionally intense. If you’re curious why the brain bothers dreaming at all, Why Do We Dream? The Leading Scientific Theories walks through the leading explanations, several of which touch on emotional processing.

Is imagery rehearsal therapy (IRT) actually effective?

Yes — imagery rehearsal therapy has some of the strongest evidence of any nightmare treatment, particularly for trauma-related nightmares. The technique asks someone to recall a recurring nightmare while awake, rewrite its ending or storyline into something less distressing, and then mentally rehearse the new version regularly, typically for a few minutes a day. In a randomized controlled trial with sexual assault survivors experiencing chronic nightmares and PTSD symptoms, Krakow and colleagues (2001) found that IRT was associated with fewer nightmares per week and improved sleep quality compared to a waitlist control group. Based on this and other trials, the American Academy of Sleep Medicine’s practice guide (Aurora et al., 2010) lists imagery rehearsal therapy as a recommended treatment option for nightmare disorder, alongside other cognitive-behavioral approaches. It’s not a guaranteed fix for everyone, and results vary, but it’s one of the few nightmare treatments with real trial data behind it rather than just anecdote.

How can I stop nightmares tonight?

There’s no single switch to flip, but a few simple, low-risk habits are commonly suggested as a starting point. Keeping a consistent sleep schedule, avoiding alcohol or heavy meals close to bedtime, and winding down with something calming rather than frightening content can reduce the raw material nightmares tend to draw on. Some people also find it helpful to write down a distressing dream shortly after waking and then consciously imagine a different, less threatening ending — essentially a lighter, self-guided version of the IRT approach described above. Keeping a regular dream journal can make patterns easier to notice over time, such as whether nightmares cluster around certain stressors, sleep times, or life events, and a free dream interpretation tool can be a low-stakes way to explore what a particular nightmare might be pointing to, since dream meanings are always possibilities to consider rather than fixed answers.

Do nightmares mean something, or are they just noise?

Both ideas have some support, and neither is proven as “the” answer. Some researchers frame nightmares as the brain’s way of rehearsing threats or processing difficult emotions, which is one reason certain recurring nightmare themes — like being chased, falling, or unprepared for a test — show up across so many people’s dream lives; if exam-related anxiety dreams sound familiar, Exam Dream Meaning: Why You Still Dream You’re Unprepared explores that pattern specifically. Others see many nightmares as more incidental, a side effect of however the brain happens to be sorting memories and sensations that night. Either way, a nightmare’s content is often read as a reflection of current stress or preoccupations rather than a literal message, and it’s fine to hold interpretations loosely.

When should I seek help for nightmares?

It’s worth talking to a doctor or sleep specialist if nightmares are frequent, causing you to dread sleep, disrupting your rest most nights, or connected to a traumatic experience that feels unresolved. This is especially true if you’re also noticing daytime exhaustion, mood changes, or avoidance behaviors building up around bedtime. This article is meant to explain the general research landscape, not to diagnose or treat anything, so if nightmares are affecting your wellbeing, a qualified healthcare professional is the right person to help sort out what’s going on and what treatment options, including IRT or other therapies, might fit your situation. If you’re also interested in gaining more agency inside distressing dreams, some people explore dream control techniques through our lucid dreaming guide, though that’s a separate skill from clinical nightmare treatment and isn’t a substitute for professional care.

A few things worth remembering

Most nightmares are a normal, if uncomfortable, part of a healthy dreaming brain, and having one after a stressful week doesn’t mean anything is wrong. The distinction that matters most is frequency and distress: occasional bad dreams are common, while frequent, disruptive nightmares that interfere with daily life fit the pattern of nightmare disorder and deserve more attention. If you’re curious how BrainDance handles dream entries and any AI processing involved in tools like interpretation, the BrainDance FAQ covers those details directly.

Frequently asked questions

How common are nightmares in adults?

Occasional nightmares are common across the general adult population, and research such as Sandman et al. (2013) has linked more frequent nightmares to factors like poor sleep quality and higher psychological distress. Nightmare disorder, where nightmares are frequent and distressing enough to disrupt daily life, affects a much smaller subset of people.

Can medication cause nightmares?

Yes, some medications and substances, including certain antidepressants, blood pressure medications, and alcohol or drug withdrawal, have been associated with increased nightmares in some people. If you suspect a medication is affecting your dreams, it's best to discuss this with the prescribing doctor rather than stopping treatment on your own.

Are nightmares more common in children than adults?

Nightmares are generally reported more often in childhood and tend to become less frequent with age for most people, though they can occur at any life stage. Stressful periods, illness, or trauma can trigger temporary increases in nightmares regardless of age.

Is imagery rehearsal therapy something I can try on my own?

A simplified version of imagery rehearsal — rewriting a nightmare's ending and mentally rehearsing it while awake — is something many people try independently, but structured IRT is typically taught with guidance from a trained therapist for best results. If nightmares are frequent or trauma-related, working with a qualified professional is a safer way to tailor the approach to your situation.

Do recurring nightmares always mean unresolved trauma?

Not necessarily; recurring nightmares can stem from ongoing stress, irregular sleep, or unclear causes, and trauma is only one possible contributor among several. That said, persistent nightmares tied to a specific frightening event are worth mentioning to a healthcare professional, since trauma-related nightmares often respond well to targeted treatment.

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