What are Nightmares & What Causes Them?

By Ashley Little

Jun 10th, 2022

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There are already plenty of barriers to getting a good night’s sleep, you would think once you finally managed to fall asleep, everything would be okay, right? Unfortunately, even once you fall asleep, you may have to worry about nightmares. Studies show that most adults only have occasional nightmares, but some people experience nightmares much more often.

So what exactly are nightmares, and why do we have them? What do they mean, and can we do anything to prevent them? We did the research and found the answers to all of these questions and more.

What are Nightmares?

Nightmares are unpleasant dreams with particularly vivid and disturbing content, usually accompanied by a strong negative emotional response (e.g. fear, horror, despair, anxiety, sadness, etc). 

Many of us wake from nightmares in some distress, usually with good recall of the dream’s content, and we’re unable to get back to sleep for some time. By some estimates, 40-75% of dreams are actually bad dreams, but a nightmare bad enough to wake someone up in the middle of a sleep cycle usually only occurs about once a month on average.

So what’s happening in your brain when you have a nightmare? Well, as with most aspects of dreams, scientists aren’t 100% sure. We know that nightmares take place during the rapid eye movement (REM) stage of sleep, which typically occurs in the second half of the night. REM sleep is responsible for many of our dreams, both good and bad, but researchers still aren’t sure why we dream, exactly.

We do know that nightmares are more common in younger children and teenagers, but one out of every two adults also has nightmares on occasion, and an estimated 2-8% of the adult population is plagued by nightmares on a regular basis. Women are more likely than men to suffer from regular nightmares.

According to some studies, night owls (who naturally go to sleep later and wake up later) are significantly more prone to nightmares, possibly due to the build-up of cortisol in the early morning in preparation for awakening.

Types of Nightmares and Common Themes

Like dreams, nightmares tend to have a few common themes. Among the more common themes of nightmares are: feeling lost or trapped, falling or drowning, malfunctions of phones, computers or other machinery, being naked or inappropriately dressed in public, natural or man-made disasters, failing or being unprepared for a test or exam, suffering an injury, illness or death, being chased or attacked, etc.

Related: Most Common Nightmares in Each State

Like dreams in general, nightmares are often quite bizarre and surreal, even though they may feel perfectly realistic and logical to the dreamer while you’re in it. Many people believe that dreams, and nightmares in particular, are symbolic and are not to be taken at face value or interpreted literally.

Rather, nightmares indicate that the subconscious is trying to convey important issues to the conscious mind, and to reflect one’s inner feelings towards a particular problem or predicament in waking life. 

However, there are many different schools of thought on the meaning and interpretation of dreams and nightmares, and many scientists today are of the opinion that there may be little or no specific meaning to them. According to some theories, all dreams, including nightmares, are just our brains making sense of random brain activity throughout the night.

Nightmares vs Night Terrors

There is one type of nightmare that is a little different though, and it’s the night terror (also sometimes called sleep terrors). Unlike regular nightmares, night terrors cause enough significant sleep problems that it is considered a type of parasomnia (disruptive sleep disorders). 

Also unlike normal nightmares, night terrors take place during non-REM sleep. Instead, studies show that night terrors happen during a very deep sleep stage, and they cause extreme terror. Many people wake from night terrors with a significantly elevated heart rate and they may be sweating, screaming, or crying.

Unlike nightmares though, many people do not remember the content of a night terror, and sometimes people don’t even remember having the night terror at all when they wake up in the morning. Night terrors are much more common among children, though adults may have them occasionally.

Characteristics of childhood night terrors include:

  • Sitting up in bed
  • Crying uncontrollably
  • Screaming or shouting
  • Profusely sweating
  • Accelerated heartbeat, racing pulse, heavy breathing
  • Looking terrified, confused, or glassy eyed
  • Attempting to push you away if you try to hold them

Perhaps most upsetting for you as a parent is your inability to console or sooth your child when they are in the grips of a night terror. In fact, you won’t even be able to awaken them. Most night terrors last only a few minutes, but some can last as long as 30 to 45 minutes. After that, the child will return to quiet sleep.

As traumatic as the event appears to the observer, the child experiencing a night terror will have no memory of it the next day. And rest assured, these events are not harmful and are not an indication of a mental disorder. As long as your child does not hurt themselves while kicking and flailing around or getting out of bed, the night terror will resolve on its own without injuring your child.

Although the child or adult experiencing the night terror usually returns to sleep without awakening, their sleep cycle has clearly been disrupted. They as well as their family members may experience daytime sleepiness and irritability the day after a night terror episode.

What Causes Nightmares?

Unfortunately, there’s still a lot we don’t understand about nightmares and dreams in general. But we do have a few clues about what might cause nightmares.

Generally, all dreams, both good and bad, are caused by activity in specific parts of the brain while our conscious mind sleeps. But there are other factors that could influence whether we have a good dream or a bad one:

  • Eating close to bedtime. When we eat, we supply our brains with lots of energy, which could lead to more brain activity for us to process in our dreams, which might cause more nightmares.
  • Certain medications (antidepressants, narcotics, blood pressure meds). Some medications interfere with neurotransmitters (brain chemicals) that can influence our dreams. For instance, many blood pressure medications affect norepinephrine and antidepressants typically affect serotonin while medications for ADHD and Parkinson’s affect dopamine. All of these can have a significant impact on the content of our dreams.
  • Withdrawal from meds/substances. Any time we stop taking a medication or stop using a substance that we’ve taken or used for a significant amount of time, our brain is going to need time to adjust. During that adjustment period, nightmares may be more frequent.
  • Sleep deprivation. Scientists still aren’t totally sure why, but dreaming is essential for our health. Not just sleeping, but dreaming specifically. When we don’t get enough sleep, we don’t get enough dreams, so sleep deprivation may cause our brains to try and cram as many dreams into our sleeping hours as possible, which can result in nightmares.
  • Psychological triggers (anxiety, depression, PTSD). Studies show that people with mental health conditions like anxiety, depression and post-traumatic stress disorder (PTSD) are more likely to have nightmares than those without those conditions.

The Effects of Nightmares

Nightmares are an unpleasant experience in the moment, but it turns out frequent nightmares can actually have a significant impact on our overall wellbeing. The disturbing content and intense feelings of fear, disgust, or paranoia that go hand-in-hand with nightmares can make it very difficult to fall back asleep after having a nightmare.

This can lead to sleep deprivation, which then goes on to cause a whole host of problems. One night of insomnia is unlikely to cause serious problems beyond some sleepiness, but chronic insomnia caused by nightmares can lead to all kinds of health problems, like increased risk of heart attack or stroke.

Nightmares can also have a serious impact on our mental health. Seeing disturbing content night after night can lead to more negative thoughts throughout the day. Negativity doesn’t necessarily cause depression, but a key symptom of depression is the loss of pleasure in activities, which could happen if all you can think about is your disturbing dreams.

Consistent nightmares could also lead to nighttime anxiety because you start to become afraid of going to sleep because you associate it with the nightmares.

Treatments for Nightmares: How to Make Them Stop

Clearly, nightmares can be a very real problem. So what can you do about it? According to the Mayo Clinic, there are actually several ways to prevent nightmares.

First, they recommend treating all underlying conditions that may be causing the nightmares. For example, if you have a mental health condition, seek out proper treatment to help reduce the anxiety or depression that may be causing the nightmares.

If you don’t know what’s causing the nightmares, the Mayo Clinic also has a few lifestyle changes you can make that might help you sleep more soundly:

  • Come up with a soothing bedtime routine so that you go to sleep feeling as relaxed as possible.
  • Self-soothe when you wake up from a nightmare. Keep comforting objects near your bed so if you wake up from a nightmare, you can calm yourself down.
  • Talk about your nightmares. Like most dreams, nightmares rarely make any sense when you actually start to analyze them. Talking through your nightmares and realizing that they make no sense may make them seem less powerful.
  • Rewrite the ending. Keep a dream journal and small light by your bed, and any time you wake up from a nightmare, rewrite the ending to make it less scary or upsetting. This may help you fall back asleep more quickly.


Nightmares aren’t fun for anyone, but if you have them, rest assured that you aren’t alone. Most people have bad dreams, nightmares, or even night terrors. But there really are ways to get better sleep, wake up feeling more rested, and cope with the anxiety that accompanies frequent nightmares.