October 25th, 2023 . 9 mins read

Nightmares: Understanding Their Causes & Why They Happen

By Andrew Russell, Wellness Writer

Medically reviewed by

Dr. Nayantara Santhi

Dr. Nayantara Santhi

Dr. Nayantara Santhi holds an academic position at Northumbria University. After completing her Ph.D. at Northeastern University ...
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Everyone experiences the occasional nightmare — a bad dream featuring disturbing, terrifying, or disagreeable imagery that leads to emotional distress and often forces you to wake up suddenly.

Nightmares can feel very real, making it harder to go back to sleep and potentially causing an evening of insomnia or daytime distress. Frequent nightmares can be a psychological or even physical problem that might need treatment.

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What Are Nightmares?

A nightmare is a type of frightening dream that causes you to wake up, leaving you with intense feelings of distress, fear, or anxiety. If you do not awaken from a bad dream, then it is called a dysphoric dream.

Sometimes, nightmares occur when you go through a period of high stress in your life, like if you are worried about a member of your family. They are also associated with mental or physical health problems, like neurodegenerative disorders and more.

Nightmares can be a symptom of nightmare disorder. This condition involves waking more than once due to vivid nightmares that feel like a threat to your survival or safety, according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5).

Because nightmares disturb your rest, they may affect how much sleep you get and its quality, impacting how you perform throughout the day.

What Are the Causes of Nightmares?

Dreams, including nightmares, can occur throughout the different sleep stages, from NREM to REM (rapid eye movement) sleep.

“Our understanding of dreams has vastly improved by current research on lucid dreaming, the intriguing state with a fluid boundary between wakefulness and sleep,” says Dr. Nayantara Santhi. 

“Additionally, recent advances in neuroimaging techniques have allowed researchers to relate various phenomenological dream features to well-known patterns of brain activation. We now know that certain brain areas are consistently active during dreams, irrespective of sleep stage.”

A sleep cycle is where you move through all the stages of sleep and can last roughly 90 minutes, though how much time you spend in each stage can vary by sleep cycle. The first sleep cycle will typically have more NREM sleep than the last sleep cycle.

NREM and REM sleep both play a role in the body’s upkeep, helping to regulate memory, cognition, emotions, and even some physical systems.

Nightmare symptoms include:

• Dysphoric, extended dreams that the person can clearly remember or feel when they wake up, which feature threats to one’s survival, physical integrity, or personal safety.
• Waking that is associated with rapid alertness and orientation due to feeling high stress or emotionally charged.
• Negative emotions after the nightmare, which can last and impact mood throughout the day.
• Loss of sleep associated with nightmares that impact social or mental functioning throughout the following day.

The experience of nightmares typically begins around 10 years old, although younger children can experience nightmares if they are under high stress, develop an illness with a fever, or experience trauma. Children and adolescents are more likely to suffer from nightmares, with the frequency typically decreasing into adulthood. Women are also more likely than men to have nightmares.

Nightmares are most often caused by major life events, increased stress at work or home, and trauma, like losing a loved one or surviving an accident like a natural disaster. They can also be triggered by:

• Changes in medication or new prescription medications.
• Eating just before going to bed.
• Illnesses like the flu that are accompanied by fever.
• Over-the-counter medications like some sleep aids.
• Abruptly stopping some prescriptions.

These causes may lead to nightmares for one night, a few nights, or a few weeks, depending on how the body manages chemical changes. Ongoing nightmares, or nightmare disorder, may be caused by:

• Sleep apnea.
• Post-traumatic stress disorder (PTSD).
• Serious anxiety disorders or depression.
• Sleep terror disorder.
• Narcolepsy or idiopathic hypersomnia.

Do Nightmares Have a Deeper Meaning?

Medical researchers and dream interpreters have several theories on why nightmares occur and what they mean.

Some psychologists think nightmares are a form of “threat rehearsal,” in which highly stressful and even life-threatening events play out in the mind, and you must move through them. Other researchers believe that nightmares are your brain’s way of storing and processing stressful events in your day or life.

A 2014 University of Montreal study analyzed the content of 253 nightmares and 431 bad dreams (negative imagery leading to emotional disorientation or distress, but did not cause fear or anxiety). Physical aggression was the most prevalent theme in these sleep disruptions, followed by threats to health and the threat of death.

Men were more likely to have nightmares involving war or natural disasters. Women had more frequent dreams about interpersonal conflicts. Fear was the most reported emotion from nightmares, but disgust, sadness, confusion, and grief were also associated with nightmares and bad dreams.

Nightmare disorder causes frequent nightmares. As a separate condition from other mental or physical causes of nightmares, it is an idiopathic disorder, meaning there is no specific reason for it to occur. It is characterized by recurring or frequent nightmares that disrupt sleep.

Symptoms used for medical diagnosis of nightmare disorder include:

• Frequent nightmares.
• Anxiety, persistent fear, or other significant impairment or distress throughout the day.
• Fear or stress around bedtime because of concern about another nightmare and more sleep loss.
• Trouble with memory or concentration, or an inability to stop thinking about images from nightmares.
• Problems at work, school, or in social situations due to emotional and cognitive impairment.
• Behavior problems at night or before bed.
• Fear of the dark.

Are Night Terrors a Symptom of Nightmares?

People who experience nightmares may talk, yell, or thrash in their dreams. This occurs when the brain fails to paralyze the body during REM sleep. Symptoms can range from moderate talking to going through the motions of running.

Some people colloquially refer to this experience as a night terror, but this is not the medical definition. Sleep specialists and medical professionals understand that there is a great difference between nightmares and night terrors.

Someone who experiences a night terror may shout or scream, appear scared, look like they are awake and reacting to something frightening, thrash their arms and legs, and even sleepwalk. This condition is not remembered by the person who experiences it. It is more disturbing for the person who wakes up and witnesses someone suffering a night terror.

In contrast, a person experiencing a nightmare may not physically react to the experience. However, they will wake up under stress, with a vivid memory or emotional recall of the experience.

Children will experience night terrors and nightmares more often than adults, although fewer adults experience night terrors than nightmares. For most people, night terrors begin in childhood and may last into adolescence, but they rarely continue into adulthood. Most people experience nightmares as children and are still prone to experiencing the occasional nightmare as an adult. Even babies have nightmares.

Both children and adults who experience continuous nightmares that lead to serious disruptions in sleep and ongoing daytime stress need treatment.

How Do You Stop Nightmares?

If you often struggle with nightmares and lose sleep because of this problem, you need to know how to manage this condition. Working with a doctor or therapist to diagnose any underlying mental or physical causes of nightmares, like sleep apnea or mental illness, is a crucial first step.

Once you have an understanding of the causes of your nightmares, you can develop an approach to managing or treating the problem. The best options include finding ways to reduce your stress, like getting a higher quality mattress to sleep better, taking an herbal supplement that eases you into sleep, working with your doctor on prescription treatments, or using devices to manage your sleep disorder.

According to the DSM-5, the best approach to treating nightmares starts with social support from friends and family, which can reduce stress. Consulting a mental health professional for treatment after a stressful event like the loss of a loved one or trauma can help to manage PTSD symptoms, anxiety, or depression associated with these significant personal changes.

Physical illnesses like sleep apnea can be addressed with regular exercise and a healthy diet. This helps you maintain a healthy weight, which, in turn, reduces breathing-related sleep disorders.

Experiencing nightmares more than once a week on a regular basis requires medical attention. Work with your general practitioner first. Then, work with specialists you may be referred to.

Medical Remedies

Experiencing nightmares more than once a week, which prevents you from getting a good night’s rest and impacts your daily activities due to lost sleep over a long period, should be reported to your doctor. This can indicate a possible medical condition that requires treatment.

Tests to determine underlying causes of nightmares at this frequency include:

• Blood tests.
• Electroencephalogram (EEG).
• Liver tests.
• Thyroid tests.
• Polysomnography (sleep test).
• Other neurological or psychological assessments as needed.

Your doctor may also use a questionnaire like the Disturbing Dream Nightmare Severity Index (DDNSI), which features five questions that are designed to evaluate your personal experience of nightmares. Understanding how distressed you are and how often your nightmares occur can help your doctor determine the best course of action for you.

If your doctor has prescribed a new medication and you begin experiencing nightmares shortly after starting treatment, report this symptom to your doctor. They will likely tell you to stop taking the drug, switch you to a new drug, or adjust the dose of the drug. Do not make any changes on your own without working with your doctor.

For people experiencing nightmare disorder, working with a therapist to apply cognitive-behavioral therapy (CBT) techniques and sleep hygiene can regulate how often you experience nightmares. Imagery rehearsal therapy (IRT) is a form of CBT in which you recall images from a nightmare that impacted you, especially if the images recur. Then, think about more positive images that could take their place, and write these down as a narrative. By writing a new story, you mentally rehearse a new scenario to replace the old.

The Academy of Sleep Medicine recommends this approach to nightmare disorder treatment. Studies involving IRT show that it is a very effective form of mental health treatment.

Natural Remedies

If you do not want to take sedative medications to get more sleep, or you have not had a good experience with prescription medications to manage your nightmares, ask your doctor about some integrative medicine options like herbal remedies or supplements. You may wish to try these:

• Valerian root
• Hops
• Passionflower

These herbal remedies can come in the form of an over-the-counter pill or dietary supplement, or you can brew the herb directly into a tea to drink before bed.

You may also benefit from vitamin supplements or foods that are high in these vitamins and minerals:

• Omega-3
• Tryptophan
• Magnesium
• Vitamin D

Essential oils have been shown to enhance relaxation, which can help you fall asleep faster and sleep more soundly. The following are recommended essential oils:

• Lavender
• Chamomile
• Vetiver

Simple Home Remedies

Taking care of your mental and physical health with lifestyle changes and home management enhances any natural or medical approaches to reducing nightmares.

• Regular exercise can physically tire you out, so you get deeper sleep. It can also help to manage your brain chemistry to reduce anxiety and depression symptoms that can affect your sleep.
• Limit some food and drinks, like those containing caffeine, so you sleep better at night.
• Take time for yourself, which can support your mental health.
• Try mindfulness or deep breathing to help you relax.
• If you feel tired or sick regularly, or uncomfortable as you try to sleep, consider taking some time off from work or school so you can relax and de-stress. If you can’t, learning time management tips and ways to manage stress can make your days easier.
• Establish a routine of going to bed and getting up at the same time every day to help you get better quality sleep more often.

Some people benefit from keeping a dream journal or talking about their bad dreams to loved ones or a therapist. This can help you gain perspective on potential causes of stress or anxiety that may have led to bad dreams.

If you are watching a television show or listening to a podcast that has fear, stress, or negative images associated with them, you may consider limiting your exposure. For example, if you enjoy horror movies, limiting how often you watch these can help you get better sleep.

Healthy sleep hygiene habits include eliminating blue light from your evenings. A few hours before bed, stop using a screen like a computer, phone, or TV. Additionally, eating right before going to sleep increases the risk of nightmares, so eat a lighter, healthier dinner about two hours before going to bed and avoid “midnight snacks.”

If you struggle with nightmare disorder or frequent stress leading to nightmares, you may find that a change in scenery can improve your ability to sleep. Often, trouble sleeping like insomnia or nightmares can lead to a negative association with your bed, your bedroom, or your bedtime routine.

Getting new pillows, bedding, and even a new bed or bed frame can improve the quality of your sleep. You can find the best mattress for your body and remove potential allergens or dust particles that make it hard to sleep. You can even create a new sleep arrangement that you do not have negative associations with. This change can help you re-learn to enjoy resting and falling asleep.