Parasomnias include a number of events that occur during sleep and cause disruption during the night. I sometimes refer to them as 'things that go bump in the night'. They include sleepwalking (somnambulism), sleep talking, confusional arousals, night terrors, sexsomnia, automatic behaviour, bed wetting (enuresis), nightmares and REM behaviour disorder amongst others.


Parasomnias that occur during non-REM sleep are called non-REM parasomnias (see below), but events can also occur during REM sleep. The basis of non-REM parasomnia relates to some parts of the brain having roused from sleep, and performing wake-like activities. Because the conscious centres remain in stage 3/4 delta slow wave sleep, the subject is technically asleep and unaware of their actions. There might be an evolutionary basis for this, because migrating birds are thought to take hundreds of brief ’powernaps’ whilst flying, showing that some parts of their brains are asleep, whilst others that control flight continue to function. Subjects will have their eyes open, but are not actually processing information as they would during the day, although they can perform tasks that seem to require underlying sensory input.


Because delta wave sleep occurs early in the night, events are usually noted within the first 90 minutes or so of sleep.


Non-REM Parasomnias
Sleep talking
Sleep walking
Night terrors
Bruxism (tooth grinding)
Confusional arousals
Sleep eating disorder
Complex behaviours in sleep


Sleep talking

Vocalising in sleep is one of the most common of this group of disorders. It is frequent in children who usually grow out of it, but occurs in adults also. Sometimes vocalisation is loud, even shouting or calling out, and may be sensible or nonsense in content.


In my experience, the most common association in adults is with Obstructive Sleep Apnoea (OSA), when it is often present with restless flailing of the arms during the arousal process at the end of each apnoeic event.


Sleep walking

Somnambulism is the medical term for sleep walking, and is a common disorder in children. The subject is in deep sleep, but the brain centres that operate walking have aroused, and getting out of bed and wandering around the house results. It is made worse by tiredness and stress, and there is the possibility of injury if a collision with an object or a fall occurs.


Sleep walking needs to be distinguished from REM Behaviour Disorder (REMBD), where dream enactment occurs due to loss of REM related muscle paralysis. Sleepwalking during non-REM sleep generally occurs early in the night, whereas REMBD usually occurs later in the night, with movements relevant to the dream recollection.


The subject will not remember being up, and can usually be led gently back to bed. It is recommended that they are not deliberately woken because they may be confused and aggressive as they emerge from deep sleep.


Night terrors

Night terrors are very common in children before puberty and are generally harmless. Most children grow out of them as they get older. The child will wake and sit upright with staring eyes, and may scream. Although it is very disconcerting and possibly frightening for the parents, waiting until the event ends, usually a minute of so, will lead to calm again. The child should not be woken because, as with sleepwalkers, they may be confused, agitated or frightened. It may be worth checking to see whether they are rousing due to snoring, and if so to seek medical advice about enlarged tonsils causing breathing dysfunction during sleep.


Night terrors in adults are more likely to be REM Behaviour Disorder (REMBD), or waking from nightmares.


Bruxism (tooth grinding)

Bruxism turns up very frequently as part of the routine medical history when asking about sleep problems. It is often seen with obstructive sleep apnoea, and is worsened by tiredness and stress, as are the symptoms of Restless Legs Syndrome. Dentists often pick it up because of the wear and flattening that occurs to the biting surface of the teeth. Many patients wear a mouth guard at night to protect the teeth, and bruxism makes patients who snore or have sleep disordered breathing more difficult to treat with a Mandibular Advancement Splint.


Bruxism is very irritating for bed partners, who have to put up with the grinding noise. Unfortunately it is difficult to treat, and although I have tried drugs that may work in Periodic Limb Movement Disorder, they are not very successful. Some advocate using Cognitive Behavioural Therapy if anxiety or stress are possible underlying factors.


Confusional arousals

If arousal from deep slow wave sleep occurs, the brain may not function normally and becomes confused as it wakes. Thought processes and logic lag behind consciousness, sometimes referred to as ‘sleep drunkenness’.


The subject misinterprets things in the room that they see. For example, females suffering from confusional arousals in my experience almost always see spiders, on the bed, the ceiling or on the room. A door knob may become a snakes head or the ceiling may appear to be falling in. The subject is slow to respond and cannot think clearly, but may experience fear. Once properly aroused from sleep, the parts of the brain that interpret visual input respond normally and the subject thinks clearly and becomes orientated.


Confusional arousal lead to disrupted sleep for the subject and the bed partner, who may well instigate a referral to the sleep centre.


I well remember waking with a confusional arousal when I was a junior doctor. The telephone rang in my on-call room at about midnight, and I sat up on the edge of the bed and stared at it, wondering what it was. I hoped that if I did nothing it would stop ringing and ‘go away’, but, of course, it didn’t. Suddenly I woke completely and realised that it was a telephone and that I needed to answer it – which was just as well because it was the Intensive Care Unit who needed to speak to me about a patient.


Factors that may lead to confusional arousal include exhaustion and lack of sleep (as in my case above), stress, alcohol and drug abuse, and have a tendency to run in families. Arousal from deep sleep can also occur in Obstructive Sleep Apnoea and limb movement disorders, which should be investigated if there is a history of these conditions.


If there are no underlying medical factors requiring treatment, confusional arousals are harmless enough, and may respond to reassurance or CBT if there is underlying anxiety. Alternatively mild sedatives may help as a last resort, and gabapentin may have possibilities, because it is known to stabilize transitions between sleep stages.



Sexsomnia is a very unusual condition that has been recognised as a disorder of sleep only fairly recently. It refers to sexual activity occurring when the subject is sleep, and unaware of their action. It is classified as a type of parasomnia, and there is usually a history of other parasomnias occurring in childhood or adulthood also. It is usually more significant for the sleeping partner than the subject, because they may have to ward off unwanted sexual advance in the night when they wish personally to remain asleep. The subject has no recollection of the event at all when confronted with the story afterwards.


Activity occurs in both sexes, but attempts to have sex are possibly more common in males, whilst masturbation is more likely in females. The sleeping partner is often psychologically distressed by the event, and finds it difficult to believe that such co-ordinated acts can occur without the subject being aware of what they are doing. The subject will often be open-eyed which makes it even more difficult for the partner to accept. The subject may be embarrassed and find their actions difficult to reconcile when they find out.


Another problem that may arise surrounds the possibility of inappropriate behaviour or attempted rape, in which case a legal defence of sexsomnia and diminished responsibility may arise. Quite a number of reports of Sexsomnia being used as a defence have appeared over the last few years, and alcohol is often involved which further muddies the waters. Whilst some cases have been acquitted, a rising number are convicted as juries become more sceptical about defendants jumping on the bandwagon.


Activity occurs during non-REM sleep and is therefore classified as a non-REM parasomnia. As with other non-REM parasomnias, it is likely to occur early in sleep.


The only way to be sure that the events are involuntary and beyond control is to prove that the subject is actually asleep, but this requires recording one during polysomnography, with all the attendant problems that entails to make this particular diagnosis.


Good sleep hygiene to avoid excessive tiredness is good advice. Overtiredness from other causes of non-restorative sleep such as Obstructive Sleep Apnoea (OSA) and Periodic Limb Movement Disorder, or the use of excessive alcohol or sedative drugs can precipitate the problem, and these need to be assessed and advised upon or treated if necessary. As a last resort, it may be necessary for the partner to sleep separately if they are distressed by the events and cannot tolerate the disturbance.


Drug treatments are similar to other parasomnias, and a trial of a benzodiazepine such as clonazepam may be helpful.


I have seen two patients recently who reported sexsomnia after being referred by general practitioners, which reflects the fact that it is an unusual condition.


The first was a middle aged female with a normal body mass index whose husband reported that she masturbated every night and woke him up as a result. He refused to attend the outpatient appointment with her and the exact history of the events was therefore taken second-hand from the patient, who was unforthcoming and very embarrassed. She refused admission for polysomnography, and was tried with a course of clonazepam but reported little effect when telephoned for a progress report. She failed to attend for follow-up in outpatients to discuss the problem further and was not seen again.


The second patient was a young married man whose wife complained that he made sexual advances frequently when she was asleep, and that it was spoiling their relationship. After advice that they might try treatment with tablets, they both refused and said they would prefer to remain untreated, but were going to seek marriage counselling.


Sleep eating disorder

Two disorders relate to eating during the night: Night Eating Syndrome, and Nocturnal Sleep Related Eating Disorder.


Subjects suffering from Night Eating Syndrome (NES) are awake and aware of their actions, and it can be argued that this does not constitute a sleep disorder, but is more related to an eating disorder. Subjects ingest excess calories by bingeing in the night, and seem to be addicted to raiding the fridge. It is more common in women, and weight gain is common. The fact that there are trips to the kitchen in the night to eat (although sometimes food is left in the bedroom) obviously means that sleep is disrupted and there is a degree of insomnia.


In contrast, Nocturnal Sleep Related Eating Disorder (NSRED) involves the subject eating whilst asleep, and is therefore a complex automatic behaviour regarded as a parasomnia. There may associated conditions such as sleepwalking to get to the food, or Periodic Limb Movements during Sleep.


Subjects may eat bazaar inedible objects such as cigarette sandwiches, or paper, and eating seems to be out of normal control. Use of kitchen utensils such as knives can constitute a danger.


Pramipexol has been tried with limited success, and the anti-epileptic Topiramate has proved more effective in some studies, but not in others, as has clonazepam. Interestingly, psychotherapy has been reported as having only limited effect.


Complex behaviours in sleep

Complex automatic behaviours can occur during sleep consituting the undertaking of patterns of behaviour and performing tasks.


Sometimes behaviour can be very complex. I have a patient who gets out of bed frequently and goes downstairs in his sleep. Once in the kitchen, he puts butter all over the washing up sponge and puts it in the microwave. Another patient referred recently goes down to the kitchen and feeds the birds by throwing porridge oats out of the kitchen window. Unfortunately the window is shut and his wife is getting rather fed up with finding the mess!


There are reports of subjects attempting to cook meals or drive when asleep, or visiting the neighbours and ringing their doorbell in the middle of the night.


Automatic behaviour is also frequently reported in narcoleptics during micro-sleeps.


Needless to say, this type of parasomnia has been used in court as a defence during legal cases including murder and rape (see Sexsomnia).


Automatic behaviour occurs frequently when we are awake, because there are parts of the brain that can perform tasks independently of consciousness. We are not always ‘thinking about what we are doing’. We frequently perform routine tasks whilst not registering them, for example, washing up the dishes or walking down the road. Some people report that they have driven several miles without recollecting any details of the journey, gear changes or steering, although in an emergency they will suddenly ‘snap out it’ and become aware indicating that sensory input is being processed and acted upon normally.


Firstly, the environment needs to be made safe, because there is the potential for injury. The bedroom may benefit from having a lock fitted, and the windows should be checked to reduce opening. Relacation to the ground floor may be necessary.


As with other parasomnias, investigations should exclude causes of arousal from sleep related to breathing and limb movement disorders, and reducing exhaustion through good sleep hygiene, or reducing stress or anxiety with Cognitive Behavioural Therapy may help. Drug treatments include melatonin, clomiprimine or sedatives such as clonazepam.