Aside from its name, this sleep disorder has nothing to do with the Moon. Yet because it is exceptionally interesting, let us also dedicate some space to it here. Mythology connects the Moon with many earthly events, while science has so far confirmed only some of them. Undeniable is its influence on water in the oceans. Tides are highest at the full moon, because that is when the Moon’s gravity is strongest. What strikes me is the claim that it does nothing to the water in the human body, where there really is a lot of it, just as it moves tons of water in the oceans. In addition to water there is an entire range of marine animals, from corals to fish, that have their internal clocks—oscillators—set circalunar as well, that is, according to lunar phases. When life emerged on land, a bit of that remained with it, and some events, especially reproductive ones, are associated with lunar cycles. Empirical observations suggest that more children are born at full moon than at new moon.
All magicians and witches have been drawn to the full moon since Babylon, through Bulgakov and his extraordinary novel The Master and Margarita, which portrays Satan’s Easter full-moon visit—and us too. However, one can say with certainty only one thing: all people sleep 10–20 minutes less than their long-term average, which is due to reduced secretion of the hormone of darkness, melatonin. Several small studies suggest that men have longer REM phases at full moon, while women have shorter ones.1 Sleepwalking has nothing to do with this, except perhaps that it is easier to notice.
This weekend police covered a naked sleepwalker in Manchester after finding him wandering the streets. The man apparently found a funny side to the nightly adventure when he asked the police who found him for a selfie.
That brings us to the sleep cycle and its structure. Around nine o’clock in the evening, the pineal gland, or epiphysis, starts secreting melatonin, the sleep hormone, and it continues throughout the night until almost seven in the morning. After around six in the morning, cortisol, a stress hormone, is released sharply; it prepares us for daytime strain. One of its roles is to erase memory traces, and that is why we quickly forget the morning dream. Otherwise it primarily activates the whole organism.
In the brain we have a complex clock, an oscillator that allows physiological processes to be synchronized with the solar rhythm. All events have cycles, and by their length we determine circadian rhythm (about a day), which lasts 24–28 hours. Slower rhythms, such as the female menstrual cycle, are called infradian, while the faster ones, for example heartbeat, are ultradian.
Circadian rhythm has two nodal points, spring and autumn, when short day and long night switch into their opposite. Among us, there is a certain percentage of people for whom this change causes confusion in the clock, which can manifest as depression and/or psychosomatic symptomatology. These are typical spring and autumn depressions, for which we find no psychogenic reasons and therefore they appear “for no reason at all.” April is thus the month with the highest suicidality, and in autumn, with summer’s residual strengthening, this extends to November.
Within the time window in which melatonin is secreted, we should spend 7–9 hours asleep. As the Czech fairy tale says, this is the sweetest thing in the world; unfortunately it is often disturbed. During normal physiology a person falls asleep within 20 minutes of lying down and then gradually descends through lighter stages characterized by slow waves on EEG into the deepest sleep (stage 4), whose electroencephalographic record resembles unconsciousness but remains slow-wave. Roughly after 90 minutes, a sudden arousal of the organism appears together with dreams and outwardly visible rapid eye movements; this phase is then labeled REM (rapid eye movement). At the same time, the EEG record approaches the waking record and differs markedly from slow-wave sleep phases, while waking up still feels far away in this state. If the person wakes within five minutes after the end of REM, the dream is remembered; over a longer time window it is forgotten, and in the morning one has the impression that nothing was dreamt, although about 15–20% of total sleep is spent in REM. This cycle repeats and then sleep becomes shallower, REM appears more frequently, and some of these episodes end with awakening. Morning dreams are also forgotten because cortisol, which ramps up to help us survive the day, erases the memory trace.
True sleepwalking, somnambulism, is a partial arousal state that occurs during slow-wave sleep, that is, not in REM, so not in dreams. In current global classification, somnambulism belongs to the group “disorders of arousal” (DOA – disorders of arousal)2, formerly known as parasomnia, which is a kind of umbrella label for classical sleepwalking, parasomnias of the sexsomnia type, sleep-related eating disorders, sleep terrors, disorders induced by some medications, now expanded to include REM-related disorders (RBD – REM behavioral disorders) and sleep apnea syndrome. It is increasingly clear that these arousal disorders are not limited to childhood and adolescence, and that 2–4% of the population in adulthood suffers from them.
I have been a sleepwalker all my life. My parents went crazy about it, and so that I would be safe as a child, the windows in my room were always locked. I often wandered into my parents’ room and stood silently at the end of their bed—sometimes mumbling nonsense. I can only imagine how frightening that must have been. My mother remembers one night, when I was about 12, when I got upset after telling her she had never listened to me, even though until then I had been speaking total nonsense.
If there is family occurrence, hereditary influences are contentious, because so few studies focused on this topic exist so far. As for distribution, men and women are affected equally in a 50:50 ratio. There is a risk of injury and harming others in all cases, sexual assault to varying degrees in the case of sexsomnia, pseudosuicidium (a fatal injury mistaken for suicide) in an unfortunate fall from a window. People with these disorders can often suffer from daytime drowsiness, various pains, and overall reduced quality of life.
A sleepwalker should never be awakened, because after such an awakening they are confused and behave confusedly, unpredictably, and not rarely aggressively. It is best to speak to them quietly, and one can usually establish a conversation, while at the same time guiding them back to bed and laying them down.
The idea that behavior in partial arousal states is fully automatic action is now being challenged, and it is now being shown that even in classic sleepwalking it can be a response to dream content. Even though it is not entirely clear how these disorders arise, it seems demonstrated that the brain sleeps halfway in frontoparietal areas, while it is “awake” in the motor and limbic (=emotional brain) areas.
The summer before I went to university, I somehow managed to open a window as far as possible. I had to practically hang out of the window. My mother feared that when I went to university I would do something so dangerous while sleeping. I was reasonable and made sure I always locked the windows and doors so I could not climb out while I was in the dormitory.
Historically, several typical situations are credibly documented: In the third century of the Common Era, the Stoic philosopher Diogenes Laertius is said to have read and written his works while sleeping. In the second century, Galen, the “father” of anatomy, in his work “De motu musculorum” (On Muscular Motion) stated that he spent the whole night walking in sleep and woke up only after stumbling over a stone. In the Middle Ages, sleepwalking and other sleep disorders were inseparably tied to religious faith and interpreted as divine signs or demonic deeds. The 16th-century Spanish writer Antonio de Torquemada wrote that the devil forces us to “dream indecent dreams” and provokes sleepers “to madness, for which we may one day lose both body and mind.”
My partner knows how to get me back to bed. The only thing they need to do is to speak gently and calmly so they can persuade me back to bed. Often I then wake up in bed and we laugh about it. If I had been sleepwalking during the night, I wake up completely exhausted. I know that I did it only when I wake up in the middle of sleep or when someone tells me so. It feels more frightening when I wake up without realizing that they had to stop me from going to the kitchen or to the car.
The manifestations of the disorder usually appear in the first third of sleep, that is, before midnight, in the second stage of slow-wave light sleep at the behavioral level, in uncontrolled behavior when the sleeping person gets up, has open eyes and a distant expression and starts behaving as if awake, while not being aware of their behavior. Often only routine things are done, those usually performed routinely during wakefulness. They may speak in their sleep, move around the apartment, and may nonsensically move objects, but can perhaps under the influence of dream content cross normal limits and get into very dangerous situations, endangering their own safety and health, for example by beginning to cook, or setting off to drive a motor vehicle, or harming someone else3. Aggressive manifestations usually appear in the first third of the altered state, and after awakening a certain degree of confusion and blurred reality persists for several minutes. A dark-state episode may last from minutes to three-quarters of an hour. Memory loss need not be complete: around 75% report fragmentary memories of what happened.
Diagnostic criteria include the following items: A. Recurrent episodes of apparently awake behavior during sleep, which may, however, be very irregular in time, for example after several months. B. Inadequate or completely absent response to efforts from the environment to wake the sleeping person. C. Limited or entirely absent relation with some dream (non-REM) event. D. Complete or partial amnesia for behavior that occurred. E. The disorder cannot be explained by another mechanism (intake of psychoactive substance, neurologic-type seizure disorder, another psychiatric disorder).
The only objective method for diagnosis is, however, an overnight polysomnographic recording in a sleep laboratory, which captures deviations both in the brain and in the body.
One third to one-half of similarly affected individuals sustain some injury during life. Particularly interesting is the altered pain sensitivity and conduction. When, during their activity, they injure themselves, and this is sometimes quite severe (fractures), most do not feel pain. From that injurious excursion back to bed and only then, when they wake up, do they perceive the pain. In the study by Lopez et al. 4, nearly 80% of patients who sustained an injury had not felt their pain at all until awakening.
The features that can be combined with undesired behavior are already classified in two separately managed groups: sexsomnia and sleep-related eating disorder. Sexsomnia clearly indicates that this is either autoerotic behavior, up to a possible sleep orgasm, or attacking sexual targets, ranging from tenderness to brutal rape. Some women even experience spontaneous orgasm with loud manifestations. This behavior is usually followed during wakefulness by feelings of deep shame. People are generally ashamed of their somnambulism, but this shame is extreme. The sexuality of victims is, for the most part, entirely normal without any deviations toward any of the paraphilias.
My husband has these small episodes during the night, usually under great stress. It began several years ago—he always talked in sleep (a) and it seems this is an extension of that. When it happened the first time and the “no” did not help, I was really confused... He did not remember it the next morning. He was so distressed that he cried—he felt ruined—and I felt uncomfortable because of him.
Nocturnal raiding of the refrigerator, or sleep-related eating disorder (sleep eating disorder), is a common complaint mainly among adult women, who wake up in the morning in chocolate wrappers and with other consequences of their nighttime raids. Their food intake may be normal, bizarrely combined (chocolate poured over mayonnaise), or entirely inedible (CD). By contrast, especially children can have sleep terrors during somnolent episodes, which very often lead them into panicked escape with a high risk of injury. In children, restless legs syndrome (RLS) may also be associated, which is an unpleasant sleep-onset disorder, very often with familial occurrence persisting frequently into adulthood. Likewise, sleep apnea syndrome may co-occur.
Jill was in high school when she began to eat in sleep. Despite the fact that she brought food back to bed so she could gorge herself night after night, until the next morning she had no notion of what she had done. “I woke up with these containers or wrappers from entire boxes of cookies or biscuits on my bed or beside the bed,” said Jill, now 62 years old.
The same clinical picture but entirely different causes and development is seen in sleep disorders related to REM phase (RBD – REM behavior disorder). We have in the brain a safety brake that prevents possible behavior in REM dreams from being enacted in parallel with dream activity. This brake can switch off most often in older age in connection with progressive brain atrophy and most frequently during the early phases of Parkinsonian dementia. In this way, affected individuals then act based on the ongoing dream content in REM phase, not in slow-wave sleep as in somnambulism. What is interesting is that the milder a person is in wakefulness, the more aggressive their dreams. This is true also for cats, where this was found in the late 1960s after neurosurgical removal of the aforementioned safety brake. Since none of the drugs reliably influences this disorder, it is useful if such a person is actually tied to the bed with a strong rope, to limit undesired consequences. A detailed guide to actions once the disorder is detected can be found at link5 https://www.sleepadvisor.org/sleep-disorder-rem-sleep-behavior/.
At present, the prevailing view is that the relationship between sleepwalking aggression during sleep and aggression while awake is bidirectional and positively correlated—that is, the more of one, the more of the other. As somnambulistic actions move beyond harmlessness, such as eating and disclosing embarrassing information, and enter the domain of rape and murder, their degree of seriousness and relevance grows exponentially.
If we speak of aggression, there are many case reports in current literature including recommendations on how to proceed and what to focus on during possible court proceedings. In my youth this was still cited in some textbooks, but far more in popular literature, a detective story in which a detective followed the murderer’s clues unfailingly and finally reached the irreversible conclusion that it was himself, where he murdered in a sleepwalking state.
Although somnambulism is usually harmless, history has documented nearly 70 cases of homicidal sleepwalking. In addition to these murders, there are countless episodes of non-homicidal sleep violence in history. Forensic psychiatrist Bonkalo reviewed 50 reports of sleep violence. He was able to highlight common characteristics of the attacks. He found that the vast majority (47 of 50 cases) were committed by men and the age of the accused ranged from 27 to 48 years. In addition, childhood or family history showed strong sleepwalking, nocturnal enuresis, agitation upon waking, and nightmares (Bonkalo, 19746). Since Bonkalo’s report, interest and research regarding sleepwalking patients has expanded.
Parasomnias that lead to unlawful behavior, especially violence, are a mysterious phenomenon for medicine and law. Through a review of relevant medical literature, a general overview of current scientific findings will be provided. Although this knowledge is far from complete, it can provide certain neurobiological information about factors that predispose someone to such episodes.
Popat and Winslade7, regarding legal and ethical considerations, state that despite the absence of awareness during sleepwalking behavior, which ensures exemption from criminal responsibility, this does not exclude responsibility for exposure to worsening factors that result in these violent episodes. Individuals should bear responsibility if it can be expected that they can and should control these factors. In addition, they should undergo appropriate treatment and medical care so as to prevent future uncontrolled behavior. Establishing a legal defense for parasomnia is found to be difficult due to a strong potential for feigning, therefore specific criteria are proposed so that true and fraudulent claims about crimes committed during disturbed sleep states can be distinguished.
Sleepwalking (somnambulism) has nothing to do with the Moon except its name. During full moon, except for shortened sleep (throughout the world, as a consequence of reduced melatonin secretion due to greater illumination), nothing remarkable happens, and even less magical things. Sleepwalking is thus a sleep disorder of the partial arousal state, where the brain is half asleep and half awake. During actions in this state a person can do all sorts of things for which they later feel ashamed while awake, which is not reasonable. With the exception of aggression—which is in positive correlation with waking aggression (in RBD the correlation is opposite—the two are negatively related)—nighttime uncontrolled behavior does not reveal anything about the character of the affected person.
MUDr. Radkin Honzák psychiatrist Author’s blog: https://blog.aktualne.cz/blogy/radkin-honzak.php?itemid=45293
1We found that around the full moon, delta activity of the EEG (electroencephalography) during NREM sleep, an indicator of deep sleep, decreased by 30%, sleep onset latency increased by 5 minutes, and total sleep time assessed by EEG was shortened by 20 minutes. These changes were associated with reduced subjective sleep quality and lowered levels of endogenous melatonin. Christian Cajochen, et al.: Evidence that the lunar cycle influences human sleep. Curr Bio. 2013 5. August; 23(15):1485-8. DOI: 10.1016/j.cub.2013.06.029. 2 Idir Y, Oudiette D, Arnulf I.: Sleepwalking, sleep terrors, sexsomnia and other disorders of arousal: the old and the new. J Sleep Res. 2022 Aug;31(4):e13596. doi: 10.1111/jsr.13596. Epub 2022 Apr 6. 3Teresa Paiva 1, Hugo Canas-Simião 2: Sleep and violence perpetration: A review of biological and environmental substrates. J Sleep Res. 2022 Oct;31(5):e13547. doi: 10.1111/jsr.13547. Epub 2022 Jan 17. 4Lopez R, et al.:Pain in Sleepwalking: A Clinical Enigma. Sleep. 2015 Nov 1;38(11):1693–1698. doi: 10.5665/sleep.5144 5Sleep behavior disorder in REM sleep: causes and treatment - Sleep Advisor 6Bonkalo A: Impulsive acts and confusional states during incomplete arousal from sleep: criminological and forensic implications. Psychiatr Q 1974; 48:400–409[Medline] 7Shreeya Popat, William Winslade: While You Were Sleepwalking: Science and Neurobiology of Sleep Disorders & the Enigma of Legal Responsibility of Violence During Parasomnia. Neuroethics, 2015;8(2):203-214. doi: 10.1007/s12152-015-9229-4. Epub 2015 Apr 24.