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What are parasomnias?

Parasomnias: sleep disorders that look like a horror movie.

What are they, and how are they presented? Parasomnias are “unexpected, inopportune or undesirable phenomenons that occur at the beginning of the night, during sleep or upon awakening” [1]. Undoubtedly many of you are not familiar with the subject; however, I am sure you have heard about some of these phenomena by name. The best known are nightmares, sleepwalking and night terrors.

All parasomnias have different and particular characteristics. Therefore, below, I present a summary of the most common parasomnias according to the sleep stage in which they occur.

Parasomnias - Non REM sleep [2].

The following phenomena occur in stages of sleep in which we do not dream, so they usually happen during the first part of the night in a state of unconsciousness.

→ Sleepwalking:

Sleepwalking presents itself as a complex behaviour that can range from sitting up in bed to wandering around the house and doing meaningless activities (e.g. moving things). It is usually accompanied by a surprised facial expression with the eyes wide open.

Sleepwalking is considered a benign disorder since it does not carry any risk to does who sleepwalk. However, it is necessary to check that the activities carried out during episodes of somnolence do not represent risks for people (going out to the balcony, going down the stairs, etc.) who present this condition.

→ Night terrors:

Night terrors are episodes where people seem to act out a nightmare. These are characterise by abrupt fear reactions, facial expressions of fear, screaming, and crying. In addition, these episodes are usually accompanied by dramatic physiological responses such as tachycardia, increased respiratory rate and dilatated pupils.

So far, no studies have found a relationship between this disorder and mental problems or trauma. Therefore, it is considered a benign disorder. Plus, normally individuals who have sleep terrors do not recall this episodes or only remember them as vivid dreams.

Parasomnias - REM sleep [3]

The following parasomnias occur during REM sleep (the stage in which we dream). Usually, individuals are aware of these phenomenons.

→ Recurring nightmares:

We have all experienced a nightmare at some point in our lives: a vivid dream of unpleasant content that generates anguish or terror.

In general, we usually remember these episodes and identify them as dreams. However, when they become recurrent, they can generate a lot of distress and present unpleasant physical reactions such as difficulty breathing, and some may try to avoid bedtime.

Although nightmares do not pose risks to those who suffer from them, they are associated with psychological trauma when they are recurrent and extremely distressing.

→ Sleep paralysis:

This disorder usually occurs when waking up, but it can also happen at the beginning of sleep.

Sleep paralysis is characterised by short episodes (of seconds or minutes) in which there is an inability to speak and move, even though the person is awake. In addition, this episodes might be accompanied by feelings of shortness when breathing (despite breath normally) and hallucinations.

These episodes are very distressing for those who suffer from them because they are fully aware of what is happening. However, and like the other parasomnias mentioned above, they do not represent any risk.


In general, parasomnias are disorders whose incidence in the general population is not very high, so they are NOT typical. Also, they tend to be benign disorders. However, the experience of these can be very distressing for those who suffer them.

Therefore, when these disorders occur frequently, it is recommended to consult a specialist doctor or psychologist who can help people manage these disorders and check that they are not associated with other severe physical or mental conditions.



  1. – Pareja (2017) – p. 443.

  2. – Non-REM Sleep NON-REM Sleep: Sleep stage that contains phases 1, 2, 3 and 4 of sleep, corresponding to light sleep and deep sleep.

  3. – REM sleep: Stage of sleep whose acronym refers to Rapid Eye Movement. This stage is the stage in which we dream.


  • Pareja, A.J. (2017). Parasomnias. En Viguera (Eds.), Sueño: Fisiología y Medicina (pp. 440-463). Murcia, España.: Viguera.

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