Night Terrors: 10 Terms to Know

Night terrors, or sleep terrors, are exactly what they sound like: fits of seeming terror that occur in the night during sleep. Only a small portion of the population experiences night terrors, and they are often significantly understood. Here are a few terms to help make sense of night terrors. 

1. Parasomnia: Parasomnias are sleep disorders. They are characterized by abnormal behaviors that occur during sleep -- particularly the third or fourth stage of non-REM sleep -- that are not wanted. Night terrors are a parasomnia that often occur in tandem with other parasomnias, such as sleep walking. 
2. Nightmares: Night terrors are often confused with nightmares, but there is a distinct difference. Nightmares are just bad dreams; they occur during REM sleep, the deepest cycle, while the brain is very active and the body is virtually paralyzed. Additionally, you tend to remember having nightmares when you wake up. Night terrors, however, are characterized by thrashing and flailing, as well as screaming and crying, and are generally not recalled upon waking. 
3. REM Sleep: The rapid eye movement (REM) stage is the deepest stage of sleep. Sleep studies show the brain to be extremely active during REM sleep. Additionally, although the eyes tend to move about beneath the eyelids (giving this stage its name), the rest of the body is kept in virtual paralysis. 
4. Non-REM Sleep: Non-REM sleep is made up of 3-4 stages of progressively deeper sleep. During earlier stages, the sleeper is easier to wake, becoming less so as they pass through additional stages. Most parasomnias occur during non-REM sleep, when brain waves are slow and the body is still free to move about. 
5. Slow-Wave Sleep Phase: This is the last phase of non-REM sleep, and the stage when night terrors tend to occur. It is characterized by increased levels of delta activity. It is critical for storing new memories, and is a period when the neurons are allowed to rest and recover, making it vital for daily functioning and memory. 
6. Polysomnogram: A polysomnogram is used to diagnose various kinds of sleeping disorders, from parasomnias to obstructive breathing. A sleep specialist oversees the patient while they spend the night in a sleep lab, hooked up to sensors. These sensors are designed to record blood oxygen levels, heart and respiration rates, how much movement occurs in the legs and eyes, and how much and what kind of brain activity is occurring. 
7. Electroencephalogram (EEG): An EEG is used to record brain activity through electrodes attached to the scalp. During a polysomnogram, an EEG can help your sleep specialist determine exactly what stage of sleep you are in, based on the levels of brain activity exhibited. Night terrors generally show high levels of delta activity on an EEG.
8. Delta Activity: High levels of delta activity during polysomnograms can be indicative of a night terror diagnosis. Delta activity is one of the five different brain waves frequencies. It has a very high amplitude, and stimulates the release of particular hormones. 
9. Confusional Arousal: Confusional arousal is another type of parasomnia for which night terrors are often mistaken. It is characterized by an extremely confused state immediately upon waking up. You may seem to be awake, but continue to act strangely and feel very “foggy.” Other symptoms include difficulty remembering things, speaking slowly, and giving short answers to questions. 
10. Post-Traumatic Stress Disorder (PTSD): Night terrors are also often mistaken for PTSD. PTSD is a type of severe anxiety that develops in the wake of an extremely traumatic event. Essentially, the body’s fight-or-flight instinct continues to reappear and make you feel as if you are in danger, stimulating fear despite the fact that there is no reason for it. Some reappearing symptoms include severe nightmares, which can lead to the confusion between PTSD and night terrors.