As the name suggests, these parasomnia disorders appear during deep slow wave sleep, which is the time when a person recovers most from physical fatigue. They can cause sleepwalking, night terrors and confusional arousal, also known as “sleep drunkenness”.

• Sleepwalking is characterised by simple motor manifestations: with eyes open, the subject gets up and walks around the room with slow and clumsy movements. They may carry out more complex gestures such as opening a door, getting dressed or even going outside.
• Night terrors are characterised by short and brutal episodes generating screams and fear that can cause tachycardia, excessive sweating, etc. The subject does not react to outside interventions, and returns spontaneously to a calm state.
• Confusional arousals are characterised by disorientation. The subject seems awake but has difficulty speaking and understanding others. This can resemble sleepwalking, but in this case, the subject does not leave their bed.

• REM sleep behaviour disorders (RBD). These episodes occur during REM sleep, most often in the second half of the night. The subject enacts their dream, which can lead to violent behaviour. RBD especially affects men over the age of 50. Medication is recommended for this sleep disorder, as it can result in injury for the subject or their spouse. It is also important to look for sleep apnoea syndrome, as it can exacerbate RBD episodes.
• Nightmares are unpleasant and terrifying dreams with a feeling of oppression and anxiety that often trigger the subject to wake up abruptly, with a detailed memory of the dream’s content. They occur almost exclusively during REM sleep (second half of the night), especially in people with mood or anxiety disorders and narcolepsy. When such episodes occur repeatedly (for more than three months and more than once a week) and impact sleep quality, it is essential to see a specialist and receive treatment. This is called nightmare disorder, and psychotherapy can be useful to desensitise the patient to their nightmares. If the results aren’t satisfactory, medication may be considered, even if non-specific.
• Recurrent isolated sleep paralysis is characterised by – often minor – episodes of generalised motor paralysis when falling asleep or waking. These episodes are usually brief (a few seconds) but may cause anxiety.

• Nocturnal enuresis refers to episodes of involuntary urination (bedwetting) after the age of 5 years that occur at least twice a week for a period of more than 3 months.
• Hypnagogic hallucinations occur during sleep (hypnagogic) or upon awakening (hypnopompic), and are most predominant in women. These are mainly visual hallucinations that last a few seconds, and are often associated with sleep paralysis.
• Exploding head syndrome (EHS) is characterised by the perception of a violent noise (explosion, gun, electric shock or slamming door) in the subject’s head when falling asleep or sleeping. It may be associated with visual flashes or sensations of heat.
• Sleep eating disorders are characterised by the urge to eat and drink in a partially awake state. In addition to the consumption of high-calory products, subjects might ingest inedible products. There is often no (or very partial) memory of the occurrence.