It's common for people to think nightmares and night terrors refer to the same frightening sleep-related experience. After all, they both happen at night and they both seem terrifyingly real.
However, there are measurable differences between night terrors and nightmares.
Nightmare vs night terror: What's the difference?
In our recent discussion at this blog regarding parasomnia, we introduced the idea that there are nonREM and REM parasomnias to help differentiate certain unusual behavior patterns that occur during sleep.
What is a nightmare, exactly? Most commonly we think of nightmares as bad dreams... on steroids. The content of nightmares can be extremely scary, intense, and emotionally charged. In fact, nightmares can be so disturbing that we find ourselves waking up crying, or angry, or covered in a layer of sweat, our hearts pounding.
Nightmares are a form of REM parasomnia,which means they occur during REM sleep. Once awakened (either voluntarily or as the result of someone waking us up), we will usually remember nightmares, quite vividly.
It may take a while for us to fall back asleep, as the stress hormones released in the bloodstream during a nightmare will require time to return to normal levels.
Most nightmares take place in the middle or last third of the night, as REM sleep happens in more frequent and longer periods during this part of our sleep architecture.
Note: Most commonly, people having nightmares do not act them out due to a temporary paralysis that takes place during REM sleep. If someone is having a nightmare and they begin to act it out physically, then there is cause to believe they are actually experiencing another kind of sleep disorder: REM behavior disorder (RBD).
By comparison, what are night terrors? Also known as sleep terrors or pavor nocturnus, these are a form of nonREM parasomnia. What this means is that night terrors typically occur during transitions between sleep, with a specific association to stage 3 sleep.
Stage 3 sleep is considered "deep sleep" or "delta sleep," and it's the period of the sleep architecture when your body and brain work in tandem to repair and heal at the cellular level.
These episodes normally take place earlier in the night (the period within the sleep architecture when most stage 3 sleep occurs).
They can occur simultaneously with sleepwalking events, as well, which are another form of nonREM parasomnia.
Night terrors do not happen during "dream sleep" (REM), and so cannot be called nightmares.
The way a night terror presents, whether it be in an adult or a child, is typically more terrifying to the witness than the sufferer.
People who have night terrors engage in screaming, writhing, inconsolable crying, and intense emotional outbursts that can last 15 minutes.
During that time, they appear to be completely awake, unlike those having nightmare. Also, it is impossible to communicate with a person in the middle of a sleep terror.
Physiologically, someone undergoing a night terror can experience agitation, arousal, hypertension, large pupils, and excessive sweating... just like with nightmares, in many respects.
However, unlike those who have nightmares and can recount every last vivid detail of the experience, those who have periods of unleashed sleep terror often fall back asleep afterward and do not recall night terrors when prompted in the morning.
Can adults have night terrors?
Absolutely. It's far less common, but adults do experience this unfortunate form of parasomnia, and they are more likely to remember a fragment of a sleep terror episode. There's a more classic association between children and night terrors, however.
The parents of these kids struggle to find out what is creating such a stressful experience for their children at night; their desperation at the pediatrician's office is decidedly real and urgent and shows up in their own problems with sleep deprivation.
What are the causes of nightmares and night terrors?
What causes nightmares?
Bad dreams—however vivid—aren't by themselves indicative of a serious sleep disorder. Everybody has them occasionally. However, frequent nightmares that are distressing or preventing you from getting quality sleep may lead to nightmare disorder, a legitimate sleep condition listed by the International Classification of Sleep Disorders.
stress (ordinary varieties like domestic problems or test anxiety)
a late meal (which can trigger a more active brain caused by increased late-night metabolism)
certain medications (antidepressants, narcotics, blood pressure medication, in example)
drug withdrawal (including alcohol and tranquilizers)
anxiety and depression
the presence of other sleep disorders such as OSA or restless leg syndrome (RLS)
What causes night terrors?
As with nightmares, occasional episodes of sleep terror are not cause for concern. If they become frequent, you may wish to consult a doctor if they are accompanied by the following:
dangerous behavior or injury caused by the episodes
specific behavior patterns that repeat with each episode
sleep deprivation (from poor sleep hygiene, jet lag, or other causes)
stressful events or trauma (the loss of a family member, for instance)
fever (in children)
evidence or diagnosis of sleep-disordered breathing or restless leg syndrome
migraines or recent head injuries or concussion
the use (or discontinuation) of a new medication, or a change in medication
a history of depressive or anxiety disorders
When it doubt, ask your doctor to help you determine what a loved one's fearful nighttime patterns are caused by. A sleep professional can best assess the differences and help you with a plan for treatment, if necessary.
Whether night terror or nightmare, both are frightening to manage but, fortunately, they can be treated (or in the case of children, outgrown).
International Classification of Sleep Disorders (3rd ed.)