Night terrors in toddlers are primarily caused by an immature nervous system that struggles with transitions between deep sleep stages. Sleep deprivation is the single most common trigger, but genetics, fever, a full bladder, and emotional stress can all play a role. The episodes look alarming, with screaming, sweating, and a racing heart, but they’re a normal part of brain development and almost always resolve on their own before the teen years.
What Happens in the Brain During a Night Terror
Night terrors belong to a category called NREM parasomnias, which are disruptions that happen during the deepest phase of non-REM sleep. Normally, a child’s brain moves smoothly from deep sleep into lighter sleep stages throughout the night. During a night terror, that transition goes wrong. Part of the brain wakes up while the rest stays in deep sleep, creating a state researchers describe as “sleep-state dissociation.” The child appears awake (eyes open, moving, screaming) but is not conscious and won’t remember the episode.
Sleep studies of children with these episodes show they are significantly more likely to arouse directly out of the deepest sleep stage, called N3. This is why night terrors almost always happen in the first half of the night, typically one and a half to two and a half hours after falling asleep, when the longest stretch of deep sleep occurs. Nightmares, by contrast, happen during REM sleep and tend to strike in the early morning hours.
Sleep Deprivation: The Top Trigger
Being overtired is the most common trigger for night terrors. When a toddler misses naps, goes to bed too late, or has disrupted sleep for several nights in a row, the brain compensates by diving into unusually deep sleep. That deeper-than-normal sleep makes the transition to lighter stages even harder to navigate, raising the odds of an episode. If your toddler’s night terrors started after a schedule change, travel, or dropped nap, sleep debt is the first thing to address.
Genetics and Family History
Night terrors run in families. A large prospective study of twins published in Pediatrics found strong evidence that genetic factors influence whether a child experiences sleep terrors. At 18 months, identical twins had a correlation of 0.63 for night terrors, while fraternal twins had a correlation of 0.36. That gap between identical and fraternal twins is a classic signal that inherited biology, not just a shared household, is driving the pattern. If one or both parents had night terrors, sleepwalking, or sleep talking as children, their toddler is more likely to experience them too.
Fever, Illness, and Physical Discomfort
A fever is one of the most well-documented triggers. When body temperature rises, it can destabilize sleep architecture and make arousal from deep sleep more chaotic. Inflammation, teething pain, and general illness all work through a similar mechanism: they create enough physical discomfort to partially rouse the brain without fully waking the child.
A full bladder is another surprisingly common trigger. Toddlers who drink a lot of fluids close to bedtime or who are in the middle of potty training may experience more frequent episodes simply because bladder pressure nudges the brain toward a partial arousal. Hot baths right before bed can also raise core body temperature enough to contribute, so keeping bath time earlier in the evening can help.
Medications That Can Trigger Episodes
Certain over-the-counter medications, particularly antihistamines like diphenhydramine (the active ingredient in Benadryl), can trigger night terrors in susceptible children. These drugs alter sleep architecture by suppressing certain sleep stages and deepening others, which makes the transition out of deep sleep more difficult. If your toddler’s episodes coincide with allergy season or cold medication use, the connection is worth noting.
Stress and Routine Changes
Emotional stress is harder to pin down in toddlers than in older children, but it does appear to play a role. Starting daycare, a new sibling, moving to a new house, or any disruption to a toddler’s sense of routine can increase the frequency of episodes. The stress doesn’t need to be negative: even exciting changes like a vacation or holiday season can be overstimulating enough to affect sleep quality. If your toddler has persistent daytime fears or anxiety alongside frequent night terrors, it’s worth discussing with their pediatrician to rule out other sleep disruptions like nightmares, which feel different to the child and have different implications.
Night Terrors vs. Nightmares
Parents often confuse the two, but they look and feel very different. During a night terror, a toddler may scream, thrash, sweat, and have a rapid heart rate while appearing completely unable to recognize you. They’re extremely difficult to comfort, and trying to wake them can make the episode worse. Afterward, they have no memory of it.
Nightmares are the opposite in almost every way. A child wakes up fully, can describe what scared them (at least in simple terms), seeks comfort from a parent, and may be afraid to go back to sleep. Nightmares happen later in the night during dream-heavy REM sleep. Night terrors happen earlier, during deep non-REM sleep. If the episode occurs within the first few hours of bedtime and your child doesn’t seem to truly wake up, it’s almost certainly a night terror.
What You Can Do About Them
Since sleep deprivation is the primary trigger, the most effective prevention is protecting your toddler’s sleep schedule. That means consistent bedtimes, age-appropriate naps, and avoiding late nights when possible. Even 30 minutes of extra sleep can make a measurable difference for a child who is prone to episodes.
During an episode, the best approach is to stay nearby and make sure your child is safe, but avoid trying to wake them or hold them down. Most episodes last 5 to 15 minutes, and the child will settle back into normal sleep on their own. They won’t remember it in the morning, so there’s no need to bring it up or worry about psychological effects.
For toddlers with very predictable episodes, a technique called scheduled awakening can be remarkably effective. You track the time the episodes typically begin (often one and a half to two and a half hours after falling asleep), then gently rouse your child about 15 to 30 minutes before that window. You don’t need to fully wake them; just enough that they open their eyes or mumble before drifting back to sleep. This resets the sleep cycle and prevents the faulty transition that triggers the episode. In one study, this approach eliminated episodes in all participating children within a month of consistent use.
Medications are not a standard treatment and are reserved for rare cases where episodes are so frequent that the child is at risk of injury. In those situations, a provider will typically focus on treating underlying conditions like anxiety or sleep apnea rather than the night terrors themselves.