Night terrors happen when parts of the brain wake up while the rest stays locked in deep sleep. This partial arousal creates a state where a person, usually a child between ages 4 and 12, can scream, thrash, and appear terrified without being truly conscious or forming memories of the event. Unlike nightmares, which occur during dreaming sleep and leave you with a vivid recollection, night terrors arise from the deepest stage of non-dreaming sleep, typically in the first third of the night.
The Brain During a Night Terror
Sleep moves through cycles, progressing from light stages into deep slow-wave sleep before transitioning into the lighter, dream-filled phases. Night terrors strike during or just after the deepest part of that cycle, usually within the first 90 minutes of falling asleep. The core problem is a disconnect: certain brain regions partially activate into wakefulness while the rest of the brain remains in slow-wave sleep. Researchers call this “sleep-wake dissociation,” and it explains why someone in the middle of a night terror can sit up, scream, or even walk around while being completely unresponsive and unaware.
Brain imaging studies point to the frontal lobes and a region called the anterior cingulate as the areas most consistently involved. In the seconds before an episode begins, there’s a surge of slow, high-amplitude brain waves in the front of the brain, followed almost immediately by a burst of fast activity in the back of the brain. It’s as if two parts of the brain are pulling in opposite directions: one trying to stay deeply asleep, the other trying to wake up. Neither wins cleanly, and the result is the confused, frightened state that characterizes a night terror. One structural study even found reduced gray matter volume in parts of the cingulate cortex in people with these episodes, suggesting the brain’s architecture itself may play a role.
Why Children Are More Affected
Night terrors peak between ages 5 and 7, and most children outgrow them by late adolescence. This age pattern isn’t coincidental. Young children spend a larger proportion of their sleep in deep slow-wave stages compared to adults, which means there are more opportunities for a faulty transition out of deep sleep. Their brains are also still maturing, particularly the frontal regions responsible for smoothly managing the shift between sleep stages. As the brain develops and the proportion of deep sleep naturally decreases with age, episodes tend to fade on their own.
Genetics and Family History
Night terrors run in families, and twin studies have quantified just how strong the genetic link is. A prospective study of twins found that about 44% of the variation in night terrors at 18 months of age was explained by genetic factors, with the remaining 56% attributable to individual environmental influences. At 30 months, the genetic contribution held steady at around 42%. Identical twins were far more likely to share the trait than fraternal twins, with correlation rates of 0.63 versus 0.36 at 18 months, and 0.68 versus 0.24 at 30 months. If one or both parents experienced night terrors or sleepwalking as children, the odds that their child will too increase substantially.
Sleep Deprivation and Irregular Schedules
Anything that deepens or prolongs slow-wave sleep can increase the likelihood of a night terror. Sleep deprivation is the most common culprit. When you or your child hasn’t slept enough, the brain compensates by diving faster and deeper into slow-wave sleep the next time it gets the chance. This “rebound” deep sleep raises the arousal threshold, making it harder to transition smoothly between sleep stages and creating the conditions where a partial arousal can spiral into a full episode.
This is why night terrors often cluster around disruptions to routine: a late bedtime, a skipped nap in a toddler, jet lag, or an illness that fragments sleep over several nights. Fever is a particularly well-known trigger in children, likely because it both disrupts sleep quality and increases the body’s demand for restorative deep sleep.
Stress, Anxiety, and Emotional Factors
Emotional stress is a consistent trigger across all age groups. In children, this might look like starting a new school, family conflict, or any source of anxiety that keeps the nervous system running hotter than usual. In adults, the connection is even more pronounced. Research on adults with the sleepwalking/night terrors syndrome describes the condition as having a constitutional (biological) basis, but notes that actual episodes are often triggered by stressful life events shaped by a person’s personality, relationships, and circumstances. In other words, the predisposition is built in, but stress pulls the trigger.
Adults who develop night terrors for the first time or experience a resurgence after childhood are more likely to have co-occurring anxiety, depression, or post-traumatic stress. The relationship is bidirectional: stress worsens sleep quality, fragmented sleep increases the pressure for deep rebound sleep, and that deeper sleep creates more opportunities for partial arousals.
Sleep Apnea and Other Sleep Disorders
Obstructive sleep apnea, where breathing repeatedly stops and restarts during sleep, can trigger night terrors even in people who’ve never had them before. One documented case involved a 35-year-old man who experienced an intense night terror during treatment for severe sleep apnea. The episode was triggered by a residual breathing obstruction during a period of rebound deep sleep. The mechanism makes sense: apnea fragments sleep, which leads to compensatory deep sleep, which then creates the conditions for a partial arousal to go wrong. Treating the underlying apnea often resolves or reduces the night terrors.
Other conditions that fragment sleep, including restless leg syndrome, periodic limb movements, and gastroesophageal reflux, can act as triggers through the same basic pathway. Anything that causes a brief, incomplete arousal from deep sleep in a person who is genetically predisposed can set off an episode.
Medications and Substances
Several categories of medication can disrupt normal sleep architecture in ways that increase the risk of night terrors or closely related phenomena like intense nightmares. Certain antidepressants are among the most commonly reported triggers. Fluoxetine increases both dream recall and nightmare frequency. Venlafaxine has been linked to unusually realistic and disturbing nightmares. Mirtazapine has also been reported to induce nightmares in some patients.
The timing and dosing pattern matters too. Studies have found that taking certain older antidepressants or antipsychotic medications in a single large dose before bed consistently increased frightening dreams, but splitting the same total dose across the day eliminated the effect. Withdrawal from several drug classes, including certain sleep aids and antidepressants like trazodone, can also trigger a rebound increase in nightmares and disturbed sleep as the brain readjusts.
Alcohol is another common contributor, particularly in adults. It initially promotes deep sleep in the first part of the night but causes fragmented, lighter sleep later as the body metabolizes it. This combination of deepened early sleep followed by disrupted arousals creates a setup that favors night terrors.
How Night Terrors Differ From Nightmares
The confusion between night terrors and nightmares is understandable, but they are fundamentally different events. Nightmares happen during REM (dreaming) sleep, usually in the second half of the night. You wake up fully, remember the dream, and can describe what frightened you. Night terrors happen during deep non-dreaming sleep, almost always in the first few hours after falling asleep. The person typically has no memory of the episode the next morning, even if they appeared wide awake and terrified during it.
During a night terror, heart rate and breathing spike dramatically. The person may scream, sit bolt upright, or get out of bed. Their eyes can be open, but they aren’t processing what they see, and attempts to comfort or wake them usually make things worse or simply don’t register. Most episodes last between one and several minutes, though some can stretch longer. The best approach for a bystander is to stay nearby, keep the environment safe, and wait for the episode to pass without trying to force the person awake.
What Brings Them On: A Summary of Triggers
- Sleep deprivation or irregular sleep schedules, which increase the brain’s drive for deep slow-wave sleep
- Fever or illness, especially in young children
- Emotional stress or anxiety, in both children and adults
- Genetic predisposition, with about 40-44% of risk attributable to hereditary factors
- Sleep-disordered breathing, including obstructive sleep apnea
- Certain medications, particularly some antidepressants and sedatives, or withdrawal from them
- Alcohol consumption, which distorts normal sleep cycles
- A full bladder, sleeping in an unfamiliar environment, or noise disturbances that partially rouse a person from deep sleep
No single biochemical or structural brain abnormality has been identified as the definitive cause. Some research suggests serotonin levels or its precursors may play a role, but this remains an open question. In most cases, night terrors result from a combination of genetic susceptibility and one or more situational triggers that push the brain into an unstable state between deep sleep and wakefulness.