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What Are Nightmares?

Nightmares are dreams that may be upsetting, scary, or strange. They happen during REM sleep, also called rapid eye movement sleep. That's the stage when your brain is working hard, almost as hard as when you're awake. Nightmares are different from bad dreams, though. Nightmares will always wake you up during the night, but you’ll sleep through a bad dream. It’s normal to have nightmares from time to time.

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What Causes Them?

Dreams -- including bad dreams and nightmares -- are still mysterious to scientists. Although we don’t know what causes them, we do know about plenty of things that can make nightmares more likely.

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Anxiety or Stress

Sometimes, the daily stresses of life can bring nightmares. Worrying about school or work can make you more likely to have one. Bigger events and life changes, like moving or losing a loved one, can bring nightmares, too.

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Trauma and PTSD

It’s not uncommon to have nightmares after something traumatic, like physical abuse, sexual abuse, or an accident. For people with posttraumatic stress disorder (PTSD), nightmares are common. If you have PTSD, you might have ones that are intense and happen often. Those nightmares can also make your PTSD worse.

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Mental Health Conditions

If you're dealing with things like bipolar disorder, depression, general anxiety disorder, or schizophrenia, you're more likely to have nightmares. Your doctor might suggest things like stress-easing techniques or different types of therapy that can help keep your nightmares to a minimum.

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Some medicines can make nightmares more likely. These include drugs like:

  • Antidepressants
  • Antimicrobials
  • Beta-blockers
  • Blood pressure medicine
  • Drugs for Parkinson’s disease
  • Drugs to help you stop smoking
  • Stimulants like amphetamine and methylphenidate (like those used to treat ADHD and narcolepsy)

If you think that meds cause your nightmares, talk with your doctor. They may be able to change the medicine or the dose that you take.

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Substance Misuse and Withdrawal

If you misuse alcohol or drugs, you might find that you have more nightmares. Withdrawal from alcohol or drugs can also make them more likely. For example, opioid drugs affect parts of your body that regulate sleep. You might have heavy sleep, but you could also go back and forth between the stages of sleep much quicker. That can bring the nightmares. When you go through withdrawal and your patterns adjust again, the nightmares can persist.

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Not Sleeping Enough

A lack of quality sleep could trigger a nightmare. A common cause of dips in restful sleep is a change in your schedule. For example, if you wake up or go to bed at times that are unusual for you, or if you have a hard time staying asleep. Insomnia also is a common cause of nightmares.

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Eating Right Before Bed

A pre-bedtime meal or snack can speed up your metabolism, which can make your brain more active. If you find that you're having more nightmares, try to avoid those after-dinner indulgences.

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Sleep Apnea

This is when you briefly stop breathing during your sleep. Although doctors aren’t sure why, there is a belief that sleep apnea can make nightmares more likely. Some researchers think that the stress that can come with the condition causes them. Some research suggests CPAP therapy can lower your odds of having nightmares. In one study, 91% of participants said their nightmares went away once they had it.   

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Scary Books and Movies

Sometimes, reading a scary book or watching a horror movie can cause nightmares, especially if you do them right before bed. Video games and TV shows that scare you can also make you more likely to have one. If you notice that you usually have nightmares after you read or watch something frightening, avoid those activities right before you go to sleep.

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What You Can Do

Nightmares happen sometimes, but there are strategies that can cut your chances of having one. Try to:

  • Stick to a sleep schedule and get enough rest at night
  • Cut out alcohol, caffeine, and cigarettes
  • Work out earlier in the day
  • Relax before you fall asleep
  • Steer clear of frightening movies, video games, TV shows, and books

If these tips don't work, visit your doctor. They may be able to help you find another cause of your nightmares. 

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When to See a Doctor

It’s normal to have a nightmare from time to time. But you should see your doctor if your nightmares:

  • Disrupt your sleep
  • Happen more than once a week
  • Affect your mood or activities
  • Make you scared to go to sleep
  • Make it harder for you to do daily tasks
  • Began at the same time that you started a new medication
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Sources | Medically Reviewed on 01/21/2021 Reviewed by Neha Pathak, MD on January 21, 2021


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The Sleep Foundation: “Nightmares,” “Sleep Paralysis.”

Sleep: “Five surprising reasons for your dark dreams.”

Mayo Clinic: “Nightmare disorder: Symptoms & causes.”

Sleep Medicine: “Clinical and polysomnographic characteristics and response to continuous positive airway pressure therapy in obstructive sleep apnea patients with nightmares.”

Frontiers in Neurology: “Dreams and Nightmares in Patients With Obstructive Sleep Apnea: A Review.”

TeensHealth: “How Can I Stop My Nightmares?”

National Institute on Drug Abuse: “Connections Between Sleep and Substance Use Disorders.”

Alcohol and Drug Foundation: “Amphetamines.”

MedlinePlus: “Methylphenidate.”

UpToDate: “Nightmares and nightmare disorder in adults.”

Reviewed by Neha Pathak, MD on January 21, 2021

This tool does not provide medical advice. See additional information.

THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional medical advice, diagnosis or treatment and should not be relied on to make decisions about your health. Never ignore professional medical advice in seeking treatment because of something you have read on the WebMD Site. If you think you may have a medical emergency, immediately call your doctor or dial 911.