Why do we have nightmares? Causes of frequent nightmares and what helps
CareOps editorial team · · 10 min read
Mental wellness information and service guidance published by CareOps.
About the CareOps editorial team
The CareOps editorial team publishes these guides. Sources are linked at the end of each article; examples are illustrative, not customer stories. Product descriptions refer to CareOps Maeumi. Publication and revision dates appear above.
Read our full editorial standards →You wake with a pounding heart from a dream of being chased or falling, and you're afraid to close your eyes again. Once or twice is easy to shrug off, but when it goes on for days, you start to wonder why it keeps happening. Here is what nightmares are, why they happen and become frequent, and what you can try starting tonight.
At a glance
- A nightmare is a vivid dream that grows more disturbing until it wakes you. Nightmares mostly happen in REM sleep, so they are most common in the last part of the night.
- Common triggers include stress and anxiety, too little or irregular sleep, a major event or trauma, stopping or cutting back on alcohol, and some medications.
- Frequent nightmares that disrupt sleep and daily life may be nightmare disorder. Better sleep habits and imagery rehearsal therapy, which rewrites the dream into a less frightening story, can help.
What is a nightmare, and how is it different from a bad dream?
The American Academy of Sleep Medicine describes a nightmare as a dream that feels real, grows more disturbing as it unfolds and finally wakes you up. A scary dream that doesn't wake you is simply a bad dream, not a nightmare. After a nightmare you usually become alert quickly and remember the dream fairly clearly. Physical danger, such as being chased or hurt, is a common theme, but some nightmares center on sadness, anger or shame.
Nightmares mostly arise during REM sleep, the stage when most dreaming happens. REM periods get longer as the night goes on, so nightmares are most common in the last third of sleep, toward early morning. Nightmares that come from trauma, however, can also appear earlier in the night. Having an occasional nightmare is very common: the same academy notes that 50% to 85% of adults report one now and then. If you woke up unable to move and sensed someone in the room, that may have been sleep paralysis rather than a nightmare.
| When | After waking | |
|---|---|---|
| Nightmare | Usually early morning, REM sleep | Alert quickly and remember the dream |
| Bad dream | Any time | Passes without waking you |
| Night terror | Usually early night, deep sleep | Wake in fear but recall little |
Why do we have nightmares? Common triggers
The American Academy of Sleep Medicine notes that in most cases it's hard to say exactly why a nightmare happens. Still, some factors are known to make nightmares more likely, and often several overlap.
- Stress and anxiety: tension and worry built up during the day can carry into the night and bring more nightmares. That's why nightmares often increase during upheavals such as exams, a job change or a breakup.
- Too little or irregular sleep: being overtired or going to bed at very different times raises the risk. Sleep loss can make nightmares more intense.
- After a major event or trauma: after an accident, violence or a sudden loss, it's common to have the same nightmare over and over, as if reliving what happened.
- Alcohol: stopping or cutting back after heavy drinking can bring on nightmares. Alcohol may help you fall asleep faster, but it disrupts the flow of sleep.
- Some medications and nicotine: certain medications can increase nightmares. If they started or got worse after a new or changed prescription, don't stop it on your own; talk with the prescribing doctor.
- Other difficulties: depression, anxiety, other sleep problems or physical illness can also make nightmares more frequent.
Why do nightmares become frequent, even nightly?
Frequent nightmares tend to form a loop. A nightmare jolts you awake, it's hard to fall back asleep, and you start dreading bedtime in case it happens again. Less sleep can make nightmares more intense, and the next day's fatigue and tension carry back into the night. When daytime stress stays the same and sleep is shaken too, nightmares can go on for days, sometimes every night.
Recurring nightmares that replay the same scene after a major event are a little different. They can feel like reliving what happened. If they last more than a month alongside intrusive memories, avoidance or always feeling on edge, it's worth reading about PTSD symptoms as well.
What is nightmare disorder, and when should you get help?
Occasional nightmares are common, but when frightening, vivid dreams keep coming back so that you can't sleep properly or daily life becomes hard, it's called nightmare disorder. An American Academy of Sleep Medicine position paper (Morgenthaler et al., 2018) estimates that about 4% of adults have it. Cleveland Clinic describes the severity like this. A diagnosis is made in a clinical visit, mostly by talking through when the nightmares started, how often they come and what they're about, rather than by a test.
| Severity | How often |
|---|---|
| Mild | Less than once a week on average |
| Moderate | Once a week or more, but not nightly |
| Severe | Every night |
Before a visit, it helps to keep a record of your sleep and nightmares for about two weeks. Noting when you went to bed and woke, how many times a nightmare woke you, and that day's stress or drinking is enough. Our sleep diary guide shows how.
Five things to try when nightmares are frequent
- Keep regular sleep and wake times: get up at about the same time each day and avoid pushing through exhaustion until you collapse into sleep. Try to cut back on catching up on weekends.
- Wind down before bed: set aside about an hour before sleep to put down work and worries. Try slightly longer exhales or relaxing your muscles one area at a time. If your thoughts race once you lie down, see when your thoughts race as you try to sleep.
- Cut back on drinking before bed: if you use alcohol to fall asleep, reduce it gradually. If you've been drinking heavily for a long time, talk with a doctor rather than stopping all at once.
- Settle your body after a nightmare: turn on a light and name five things you can see in the room, or notice your feet on the floor. If sleep doesn't come, get up briefly and do something quiet, then lie down again when you feel sleepy.
- Rehearse a new ending (imagery rehearsal): during the day, pick one recurring nightmare, write a version with a less frightening ending and picture it for a few minutes each day. More on this below.
For more ways to bring your mind back to the present after a nightmare, see our guide to grounding techniques.
Treating nightmares: what is imagery rehearsal therapy (IRT)?
Imagery rehearsal therapy (IRT) is a cognitive behavioral approach in which you rewrite a recurring nightmare into a less frightening story while awake and rehearse the new version in your mind each day. It treats nightmares like a learned habit that practice can change. The American Academy of Sleep Medicine's 2018 position paper lists it as a recommended treatment for both nightmare disorder and PTSD-related nightmares.
In a well-known randomized trial of 168 women with PTSD who had survived sexual assault (Krakow et al., 2001), those who received three sessions of imagery rehearsal therapy had fewer nights with nightmares and fewer nightmares than those on a waitlist, along with better sleep quality and fewer PTSD symptoms. The changes held at three to six months. Rehearsing the revised dream daily, as homework, is a key part of the treatment.
Go gently when writing down nightmares
A dream diary can help you see how often nightmares come, but writing out and dwelling on trauma-related nightmares alone can stir up strong memories and feelings. In that case, record only how often and when they happen, and do the rewriting work with a professional who treats trauma. If writing becomes too hard, it's fine to stop right away.
How is your sleep lately? An insomnia check
If nightmares make it hard to fall asleep or keep waking you, the CareOps insomnia check (Athens Insomnia Scale, AIS) looks at falling asleep, waking during the night, sleep quality and how you feel during the day. It isn't a nightmare test, but it can show how much nightmares are disturbing your sleep. You can take it right away, with no login.
Try a self-assessment without signing inAIS · Sleep difficultiesIf falling asleep or feeling rested has been difficultStart the check →If nights of trouble falling asleep have lasted a while along with the nightmares, see what causes insomnia as well.
When to see a doctor or professional
If nightmares come several times a week for weeks, if you put off sleep because you dread it, or if daytime fatigue and anxiety are unsettling daily life, see a sleep clinic or a mental health professional. If the nightmares replay a major event, it's best to work with a professional who treats trauma. If you shout and move a lot in your sleep or have nearly hurt yourself, it may be a different sleep problem, so get it checked.
If the same scene keeps waking you, talk it through by day
Nightmares are often daytime worries and tension that weren't settled carrying over into the night. CareOps Maeumi is an AI counseling app that runs sessions with approaches such as cognitive behavioral therapy (CBT) and acceptance and commitment therapy (ACT), helps you look step by step at what's weighing on you and the thoughts that unsettle your sleep, and remembers past sessions so the next one picks up where you left off. Get the app
Frequently asked questions
- Why do we have nightmares?
- It's usually hard to point to a single cause, but stress and anxiety, too little or irregular sleep, a major event or trauma, stopping or cutting back on alcohol, and some medications are known to increase nightmares. Depression or other sleep problems can also make them more frequent.
- Is it a disorder if I have nightmares every night?
- When frightening, vivid dreams keep coming back so that you can't sleep properly or daily life becomes hard, it's called nightmare disorder, and nightly nightmares are considered severe. If it has lasted for weeks, talk with a sleep clinic or a mental health professional. A diagnosis is made in a clinical visit.
- Why do nightmares often happen toward morning?
- Nightmares mostly arise in REM sleep, and REM periods get longer as the night goes on, so nightmares are most common in the last third of sleep, toward morning. Trauma-related nightmares can also come earlier in the night.
- Is there a way to stop having nightmares?
- You can start with regular sleep and wake times, winding down before bed and cutting back on alcohol. For recurring nightmares, imagery rehearsal therapy, which rewrites the dream with a less frightening ending and rehearses it daily while awake, can help. The American Academy of Sleep Medicine recommends it for nightmare disorder.
- I keep having the same nightmare after a traumatic event.
- Recurring nightmares that replay a major event are a common reaction. If they last more than a month alongside intrusive memories, avoidance or always feeling on edge, read about PTSD symptoms and talk with a professional who treats trauma. Working through it at a shared pace is better than dwelling on the details alone.
Sources
- American Academy of Sleep Medicine, Sleep Education · Nightmares (checked 2026-10-28)
- Cleveland Clinic · Nightmare Disorder (checked 2026-10-28)
- Krakow et al. (2001), Imagery Rehearsal Therapy for Chronic Nightmares in Sexual Assault Survivors With Posttraumatic Stress Disorder, JAMA
- Morgenthaler et al. (2018), Position Paper for the Treatment of Nightmare Disorder in Adults, Journal of Clinical Sleep Medicine
This guide shares mental wellness information. If you are in immediate danger, contact emergency services where you are. Support and contact information.