How Night Terrors Work

Night terrors shouldn't be confused with other parasomnias (a general name for some of the weird stuff that can happen when you're sleeping) like sleep paralysis, sleep apnea and plain old nightmares.

When people experience sleep terrors, they often yell and flail wildly. Unconscious of their surroundings and confused, they don't respond to any attempts to soothe them but instead mutter or yell. Their eyes might even be open (which is really freaky) with pupils dilated, heart racing and lungs hyperventilating. All this can go on for 20 minutes, and while it's terrifying for people in the vicinity, the sleeper doesn't remember the horrific visions come morning, though he might recall the fear [source: MedlinePlus].

Night terrors, or sleep terrors as they're sometimes called, are usually experienced by little kids. It's uncommon, but not unheard of, for adults like Jules Knight to endure them on a regular basis.

Nobody is absolutely sure how many kids get night terrors, but some estimates put it around 6.5 percent of the population between the ages of 4 and 12 (although some kids can experience them as early as 3). There's some controversy here, as one study has estimated that 40 percent of kids between 2.5 and 6 years old get them [source: BabyCenter]. Compare that with only 2.2 percent of the adult population [source: NSF].

Sleep terrors know no genders. Boys and girls, men and women are all equally prone to them. Almost nobody gets the terrors past the age of 65, which is a nice side-effect of aging.

While night terrors remain somewhat mysterious, researchers do know that they have something to do with over-stimulated central nervous systems (CNS). Our CNS is still maturing when we're kids, so that could explain why kids disproportionately experience night terrors.

Researchers also know when exactly in the sleep cycle night terrors make their unwanted entrance: It's when we go from stage 3 non-rapid eye movement (NREM) to stage 4 NREM, just as the delta waves in your brain start to slow down along with your heart rate and blood pressure [source: Borelli]. This can happen anywhere between one to three hours after we fall asleep.

That's all very well, but what are stages 3 and 4 of NREM, to say nothing of stages 1 and 2? And why do those stages contribute to all this wide-eyed sleep mania?

A quick overview of sleep cycles is needed.

We spend roughly a third of our lives sleeping, and even though it looks like nothing is going on, there's a lot happening when we slumber. Studies indicate that when we feel sleepy, a chemical called adenosine is starting to accumulate. Neurotransmitters like serotonin signal the brain that it's time to shut consciousness down for repairs. Then, as we become drowsy and fall asleep, we enter the first of five stages.

In stage 1, we're halfway between sleeping and waking, and things could go either way depending on the circumstances. Given an appropriate setting, we start drifting into stage 2, which is where we typically spend 50 percent of our sleep time. During stage 2, eye movement stops and brain waves slow down. Delta waves, which are super-slow brainwaves, start up in stage 3, and by stage 4 all we've got are those slow, slow delta waves washing through our sleeping minds. Stages 3 and 4 are known as deep sleep, and that's when we're so far under it's hard to wake us up. After that, it's on to the REM stage, during which our eyes start twitching around, breathing gets shallower and our muscles are paralyzed. This is when we have most of our dreams. REM lasts for about 25 percent of our sleep time. Then it's back to stage 1, and it all cycles around again. Each cycle lasts around 90 minutes [source: ASA]. That's why it's possible to have sleep terrors more than once in a given night. Each stage appears to have a different physiological function, which could be why we have more than one of them.

Deep sleep (stages 3 and 4) is when our tissues repair themselves and when our body releases hormones, such as the growth hormones necessary for childhood development. The REM stage energizes our brains and enhances our performance of waking life activities.

We mentioned that sleep terrors typically show up during the transition from stage 3 to stage 4, right in the middle of the deep-sleep portion of our night when the delta waves take over and some important hormonal and regenerative activity takes place. This makes them distinctly different from nightmares, which occur during REM sleep. That's also why we rarely remember night terrors, whereas nightmares can remain vividly imprinted on our memories. It's not clear whether those hormonal and regenerative activities have anything to do with sleep terrors.

The literature isn't clear about what exactly happens in the brain during a sleep terror, other than to remark that they seem to be triggered by inexplicable snags in that sleep-stage transition. Those snags, in turn, appear to have something to do with the development of the central nervous system. Studies indicate that the CNS doesn't fully develop until we're 25, which could help explain why some young adults also suffer from night terrors [source: NPR].

Night terrors can have multiple causes. First of all, it seems they often run in the family. They can also be triggered by stress, sleep apnea, fever, sleep deprivation, head injuries, migraines, overproduction of thyroid hormones, over-consumption of alcohol, unfamiliar sleep environments, travel or medications that interfere with the central nervous system.

In adults, sleep terrors can develop in conjunction with depression, anxiety or bipolar disorders. And a small minority of children who experience ongoing sleep terrors into adolescence can also be at increased risk of experiencing psychosis [source: Conneely].

Night terrors are no fun for anybody, but they're usually temporary problems that resolve themselves. And while they're resolving, they can disrupt everybody's night, leading to a grumpy, stressed-out, sleep-deprived family. While in the past doctors have prescribed medications like benzodiazepines to deal with the issue, this practice is rarely recommended now because the drugs can lead to other sleep-related problems.

Sometimes kids experience night terrors because their bladders are near bursting, so a simple fix is to take them to the bathroom an hour or two after they fall asleep and to limit their liquid intake a few hours before they go to bed.

Where pee is not involved, there are some other options available. A mother in the U.K. has reported that she solved her 9-year-old son's nightly, exhausting sleep terrors — which had been happening for six years — by putting special sheets on his bed. After a friend told her the problem might be triggered by overheating, Jo Fletcher bought her son Lewis sheets designed to reduce sweating [source: Daily Mail].

Night terrors often happen at predictable intervals. This means it's possible to prevent them with an effective solution called "scheduled awakenings," which involves simply waking the person before the onset of the terrors. There's even a device you can buy and place under a mattress to accomplish the task. The gizmo vibrates gently, bringing the sleeper out of deep sleep at the crucial point. According to some studies, the method works in 9 out of 10 subjects [source: Night Terrors Resource Center].

It was a quiet night in Phoenix, Arizona, when Scott Falater stabbed his wife 44 times and held her head under water in the pool. When the police arrived, Falater said he had no memory whatsoever of the entire incident. He had, he said, been sleepwalking. Falater never denied that he had killed his wife, but he said he had no reason to do so. There were no known problems in the couple's relationship and no history of violence on Falater's part. He was convicted of murder, but many sleep experts said that his sleepwalking defense wasn't as farfetched as it seemed [source: Yuhas].

Pavor nocturnus (that's the fancy Latin name for night terrors), along with sleepwalking and confusional arousal, belongs to a subset of sleep problems referred to as "disorders of arousal." One can lead to the other. Night terrors, for instance, can turn into an episode of sleepwalking.

All of these parasomnias occur during non-REM sleep. Neuroimaging of the brain during those deep sleep cycles shows that the prefrontal cortex is dialed down to idling mode, and that's where it stays even when a person is sleepwalking. The prefrontal cortex is where we get those excellent executive functions like judgment, attention and planning. At the same time, certain pathways in the brain of somebody experiencing an episode of arousal disorder can be lit up, including those controlling sophisticated motor and emotional activities. Unfortunately that profile of switched-on, switched-off functions resembles some of the brain activity that shows up when people are violent while fully awake [source: Sicari].

Suspended somewhere between sleeping and waking, the parasomniac enjoys the worst of both worlds: fully capable of violence without any of the inhibitions that control it.

However, research has shown that violence usually occurs only when an aroused sleeper is touched [source: AASM]. The best thing to do if you see somebody experiencing an arousal disorder is to let them be.