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Why Do We Have Nightmares?


Vivid, scary dreams can leave you feeling shaken, but usually they aren’t dangerous or something that requires medical help.

To understand nightmares it’s better to start with understanding dreams and when these occur while you sleep, says sleep specialist Ambrose Chiang, MD.

Sleep is made up of:

  • Rapid eye movement (REM) sleep, which is when you dream
  • Non-rapid eye movement (NREM) sleep, which includes light sleep and deep sleep

Sleep researchers say that most adults spend approximately two hours each night dreaming, but you’re only likely to remember a dream if you wake up from REM sleep.

“When you are in REM sleep, your voluntary muscles are temporarily paralyzed – except for your diaphragm and eye muscles,” Dr. Chiang says. “That’s why we do not act out in our dreams.”

When Nightmares Are a Problem

As far as nightmares, they’re not uncommon, especially in children, and occasional nightmares don’t constitute a disorder, Dr. Chiang says. But you may need to talk to your doctor or see a sleep specialist for help if you’re having recurring nightmares that lead to:

  • Anxiety
  • Fear of going to sleep
  • Insomnia
  • Sleep deprivation
  • Daytime sleepiness
  • Impaired quality of life

Other factors that can cause nightmares, Dr. Chiang says. For instance, post-traumatic stress disorder (PTSD) survivors may have a recurrent dream related to a traumatic event they experienced. Additionally, nightmares can also occur in individuals with:

  • Substance abuse
  • Stress
  • Anxiety
  • Borderline personality and psychiatric illnesses
  • Conditions that require taking certain medications, such as beta blockers, dopaminergic agonists, antidepressants or zolpidem

“If the nightmare is triggered by stress, medications or alcohol, working with your doctor can help treat the underlying symptoms,” he says. "For PTSD survivors, you may need to work with a clinical psychologist who is trained in imagery rehearsal therapy, which is a type of cognitive behavior therapy to help you change the theme, content or outcome of a recurrent nightmare. Prazoin, a prescribed medicine, is also known to be effective in nightmare disorder and PTSD.”

A Dangerous Type of Nightmare

One specific form of nightmare can be downright dangerous. If you have REM sleep behavior disorder (RBD), you can act out your nightmares. This is because RBD causes you to lose temporary muscle paralysis in your dreams due to a nervous system structural abnormality. The characteristics of RBD include:

  • Nearly 90 percent of people affected with RBD are male
  • Between ages 40 to 80, with a mean age onset of around 60
  • Violent limb and body movements - boxing and kicking - often associated with emotionally charged utterances
  • Dreams that involve self-defense, leading to intense movements in which they hit or kick the “offender”

“My Dad was a very gentle person, but he started having these intermittent RBD episodes that caused him to moan, punch and kick in his sleep in his late 60s,” Dr. Chiang says. “My mom got hit a few times, and she learned to very quickly jump out of bed when she heard my dad moan or sensed any violent movement.”

According to Dr. Chiang, it’s not uncommon for the RBD patient’s bed partner to get injured as a result, which can be mistaken as physical abuse by an emergency department physician. RBD sufferers can also hurt themselves severely by jumping out of bed in their dreams. They can collide with the bedroom wall or the furniture in the room or roll out of bed and injure themselves.

To protect RBD patients, a safe environment is essential and should include:

  • Having the bed partner sleep in a separate room or bed
  • Removing nearby knives and guns, as well as furniture with sharp edges
  • Placing mattresses on the floor or placing pads near the bed

Additionally, clonazepam and melatonin can effectively treat RBD patients.

RBD and Parkinson's Disease

Nearly 80 percent of RBD patients will develop Parkinson’s disease. This degenerative neurological disease is characterized by tremors, rigidity, problems with walking or posture and dementia. On average, it takes 12 years from the onset of RBD to the onset of Parkinson’s disease. For this reason, patients should have annual neurological exams by the physician following them.

“If something like this is going on, it’s not just a nightmare,” Dr. Chiang says. “You want to make sure you’re evaluated by a sleep specialist. If RBD is confirmed by an in-lab diagnostic sleep study, you should be followed closely by a sleep specialist or a neurologist."

Any time you’re experiencing frequent nightmares, especially if you act out in your dream, or are having sleep disturbances that affect your work or social functioning, it’s important to be evaluated by your doctor, Dr. Chiang says.

Ambrose Chiang, MD, is a sleep medicine specialist, director of Sleep Medicine and associate division director of Pulmonary, Critical Care and Sleep Medicine at University Hospitals Cleveland Medical Center. You can request an appointment with Dr. Chiang or any other University Hospitals doctor online.