Stories of Pelsnickel, Krampus and La Befana were sure fire ways to keep children off the naughty list, probably just as effective as today’s stories of the Boogeyman and the Elf on the Shelf. But when these stories are taken just a little too far, they can backfire. You may get jarred awake from a perfect Christmas Eve slumber by ear piercing screams from your elf hoping to stay on the nice list. Running into her room, you immediately try to console her but she keeps screaming. Finally calming down, you are able to ask, “Did you have a bad dream?”
If the Elf on the Shelf was doing his job, your little one will tell you a story of a bad dream or nightmare. But if she looks at you with a puzzling grimace and says “No, I was sleeping just fine”, what you probably witnessed wasn’t a Krampus-style nightmare at all, but a sleep terror. Nightmares and sleep terrors are often confused because, to parents and other observers, they can look the exact same. Years ago, sleep terrors used to be called night terrors which increased the confusion. Renaming them to sleep terrors has helped, but the confusion persists.
The easiest way to distinguish nightmares from sleep terrors is to ask "Do you experience vivid, distressful dreams?" If the answer is “Yes", then the person is experiencing nightmares. If the answer is “No”, then they are experiencing sleep terrors. Sleep terrors can also be confused with the anxiety provoking, sudden and severe heart artery blockages (nocturnal cardiac ischemias) that occur in adults with obstructive sleep apnea . These experiences are anxiety provoking with good reason, they can lead to heart attacks that kill you in your sleep and they can look just like sleep terrors. I have seen adults with both medical problems lying calmly, and seemingly enjoying a restful sleep, only to suddenly sit bolt upright with a loud gasp and wide open eyes and then state, with their heart pounding, “What just happened?”
From a sleep clinic perspective, we can easily tell the difference between nightmares and sleep terrors. Sleep terrors occur in stage 3 sleep whereas nightmares occur mostly in REM sleep. Sleep terrors also occur mainly in the first third of the night because this is when we experience most of our stage 3 sleep. REM sleep occurs more frequently and for longer periods of time in the latter third of the night and this is why we experience nightmares closer to wake up time.
Sleep terrors are an expression of our most primitive physiological fear response, but without a mental cause; in other words, we have an extreme fear response without a fearful source. If you were being recorded in the sleep clinic, the technician would see a doubling of the heart and respiratory rates, excessive perspiration  right about the same time you let out an ear piercing scream and instantly spring up from lying down. Moments later, the technician would see you lay back down and continue to sleep. In the morning, the technician may ask “Do you remember anything from last night?”. To which you would answer “Nope, pretty standard night.”
If you are an adult experiencing sleep terrors, an older and less socially astute clinician may refer to your sleep terrors as an Incubus or Succubus experience. Although these mythical figures would cause similar fear responses, the terms are no longer used for obvious reasons.
In children, sleep terrors are referred to as pavor nocturnus (fear or dread of the night) by clinicians who like to demonstrate their proficiency in Latin. Sleep terrors can begin between 4 and 12 years of age, about the same time sleep staging matures in the child’s brain. They tend to be more prevalent in girls than boys as well.
In children and adults, the severity of the sleep terror is positively correlated with a specific brainwave pattern in deep sleep. The brainwaves show more electrical activity (higher amplitude EEG) and longer periods of it compared to the brainwaves of the previous deep sleep [3,4]. There is also an understandable relationship between how frequently you experience sleep terrors and stress, sleep loss and fatigue .
Medications that are used to slow brain activity (usually referred to as central nervous system depressants) can lead to sleep terrors . Interestingly, these medications are used to treat anxiety, panic, acute stress reactions and believe it or not, sleep disorders! This means that treating one sleep disorder (e.g., insomnia) might cause another sleep disorder (sleep terrors)!
Occasional sleep terrors in children are usually a normal part of the brain maturation process. They are scarier for the parents than for their children. The best thing to do if your child is experiencing sleep terrors, is to leave them alone, don’t wake them up. Forced awakenings can actually cause more fear and confusion and make it difficult for the child to return to sleep. Just make sure they are not moving around too much when they have a sleep terror. You don’t want them to get hurt by banging into furniture or falling out of bed. Simply stand beside their bed and watch them the first few times it happens. Then, just leave them alone. They are not experiencing anything scary in their minds. Remember, it’s a physiological fear reaction, not a mental one. Resist your urge to console your little elf. If the sleep terrors don’t go away on their own within a month or so, then talk to your doctor.
When sleep terrors become problematic in children, that is, they are way too frequent or continue for far too long, they might not be part of the normal brain maturation process. Some children who experience problematic night terrors can develop personality disorders in adulthood . Talk to your medical doctor if they occur too frequently or persist for too long in your child.
If frequent and persistent sleep terrors kick in during adulthood, they can be related to alcohol and drug abuse, brain trauma and temporal lobe epilepsy  and should, therefore, be reported to your medical doctor.
Clinically, sleep terrors are considered mild if they occur more than once per month and do not result in harm to the person experiencing them or to bed partners or people trying to console them. Moderate sleep terrors occur more than once per week and still do not cause harm. Severe sleep terrors can result in physical injury to the person experiencing them or others and/or they occur almost nightly. Acute sleep terrors occur for one month or less, subacute for one to three months and chronic sleep terrors persist for more than three months .
 Anch, A., Browman, C., Mitler, M., & Walsh, J. (1988). Sleep: A Scientific Perspective. New Jersey: Prentice Hall.
 Broughton, R. (1978). Sleep and Epilepsy. In British Epilepsy Association (Ed.), Epilepsy 78 (pp.57-63). London: Palantype.
 Fisher,C., Kahn, E., Edwards, A., & Davis, D. (1974). A physiological study of nightmares and night terrors. Psychoanalysis and Contemporary Science, 3, 317-398.
 Kales, J., Kales, A., Soldatos, C., Caldwell, A., Charney, D., & Martin, E. (1980b). Night Terrors: Clinical characteristics and personality patterns. Archives of General Psychiatry, 37, 1413-1417.
 Hartmann, E. (1984). The Nightmare. New York: Basic Books.
 ICSD (2001). International Classification of Sleep Disorders, Revised: Diagnostic and Coding Manual