One time, it played out in an abandoned mine. Or was it the basement of a ramshackle wooden house? In the pitch black, I navigated by touch against rough timber planks, bumping down passages with dead ends. Panic began to creep in. Something sinister was afoot yet escape was proving impossible.

Habitual sleepwalkers might recognise what happened next. I started to wake but not completely, just conscious enough to realise I wasn’t trapped in a horror movie but was stuck under my bed – in my nightclothes, squashed against the wall under the mattress, unable to find the exit.

It was banal, embarrassing, a bit scary. And worst of all, as my brain struggled to properly engage, what had transpired remained unresolved. Why was I down there? Fellow travellers will recognise the sickly feeling of a sleepwalk interrupted: that lingering sensation of dread.

Some of us, in this club nobody wants to join, have walked across town in pyjamas. Some have harmed themselves or their bed partners. A rare few have fallen down stairs or jumped out of upper-storey windows (thank god I live on the ground floor).

Experts find somnambulism (its official name) fascinating: why it happens, what goes on in a sleepwalker’s mind, what it can tell us about the human subconscious. But it’s also difficult to study. Researchers can obviously talk to sleepwalkers after the event, but catching them in the act under laboratory conditions is another matter.

So, who sleepwalks and why? What happens during sleepwalking? Is it curable – and does it need to be?

What is sleepwalking?

A staple of popular culture, from Snoopy wandering with outstretched arms to Homer Simpson crashing into a fire station in his sleep or Will Ferrell’s snoozing stepbrothers raiding the fridge – even Lady Macbeth’s “out, damn spot!” somnambulating soliloquy – sleepwalking has typically been viewed as vaguely comic, a bit creepy and altogether mysterious. “We’re not a zombie horde,” wrote chronic walker (and Nine journalist) Kate Aubusson of her own experiences. “But with our vacant expressions and unpredictable wanderings as the rest of you sleep, vulnerable in your nighties, we can be pretty unsettling.”

Watch infrared footage of a sleepwalker and it’s not hard to believe they are experiencing something other-worldly. Indeed, it’s the basis of the Paranormal Activity series of fiction films, in which footage in the infrared style shows walkers at their most sinister.

Demonic possession aside, researchers know sleepwalking typically occurs during the first few hours of sleep, when we cycle from wakefulness to light sleep and then into deep sleep, but before we go into the dream state characterised by rapid eye movement, or REM sleep. Sleepwalking, and similar events such as night terrors, are for this reason technically characterised as “non-REM parasomnia”.

“That’s why they’re doing things that people can do when they’re awake ... but they’re clearly not fully awake.”

The basics are fairly well settled: sleepwalking is an “arousal disorder”, leaving half of your brain awake and half of it fast asleep, resulting in some odd nocturnal behaviours. It is relatively common in young children, who usually grow out of it, while up to 4 per cent of adults will experience some kind of episode, whether as a one-off or regularly.

It is typically triggered when a person is fast asleep and something begins to wake them – a noise, a movement, a breathing problem. Most people fall straight back to sleep but in the vulnerable, especially younger children, the waking-sleeping process can stall halfway, leaving part of the brain roused to action but many higher functions – responsible for reasoning, conversation and decision-making – unconscious.

Sleep is a lot weirder than we usually give it credit for. Dolphins, for example, sleep by switching off half their brain at a time, leaving the other half semi-conscious to deal with breathing and to keep (one) eye open for predators. Human somnambulists are not entirely dissimilar. Scan a sleepwalker’s brain, says Colin Tuft, medical director of the Woolcock Institute of Medical Research, and you’ll witness two kinds of activity simultaneously: the low-frequency brainwaves of deep, restorative slumber alongside the high-frequency waves typical of daytime activity.

“That’s why they’re doing things that people can do when they’re awake – like walking around or adjusting furniture or sometimes eating or cooking, or eating and sexual acts – but they’re clearly not fully awake.”

While dolphins intend to switch off half their brain capacity, though, in humans it’s clearly a glitch with no apparent evolutionary benefit. One way of looking at it, says Tuft, “is that the brain has a mechanism to promote sleep, it’s got a mechanism to promote ‘wake’ but it also has a third mechanism, which is the transition between wake and sleep, and that’s probably what’s disordered in these non-REM parasomnias. It’s also the mechanism that is disordered in narcolepsy.”

Why is sleepwalking relatively common in children?

Children are more likely to experience arousal disorders, Tuft suggests, because “the arousal pathways, and the mechanisms by which we switch from wake to sleep are probably still developing”. “And so in children, they’re going to be more imperfect and that process of transitioning from sleep to wake is going to be more likely to fail at times.”

Margot Davey, director of the Melbourne Children’s Sleep Centre at the Monash Children’s Hospital, offers another perspective, explaining that children are more susceptible to parasomnia episodes because they experience much longer periods of deep, slow-wave sleep than adults, which increases the chances of an arousal disorder. It is relatively common for children to sleepwalk once in a while or experience night terrors, a similar disorder where they typically wake up screaming or upset with no idea why, triggered by a subconscious fight or flight response. Between 15 and 30 per cent of children aged between four and 12 will have episodes of non-REM parasomnia, says Davey, a 30-year veteran of paediatric sleep studies.

“Depending on whether or not there’s activation of that fight-and-flight system during the arousal, that can influence the presentation of the waking,” Davey says. “The wakings can range from quiet and semi-purposeful sleepwalking to night terrors, which are more agitated, frenetic and distressed wakings, which indicate to us that the fight-and-flight pathway has been activated as well.

“And in the more extreme example are night terrors where there is tremendous activation of that fight-flight system, so you’ll have parents who feel like the child is possessed and something terrible is happening.”

Sleepwalking or night terrors are more likely to be triggered if a child’s sleep is disrupted by illness or if erratic sleep patterns cause them to miss out on sleep. The occasional outlying case might result from another sleep disorder such as sleep apnoea or might turn out to be a different condition altogether, such as epilepsy, Davey says. Most of the time, though, the cure is straightforward: “Making sure they get sufficient sleep is a very helpful strategy.”

“If you’ve got one parent [with a history], you’ve got probably about a 45 per cent chance of having it; with two sides there’s a much increased chance.”

Why some children are particularly prone to sleepwalking is not completely understood, although it appears there is a genetic predisposition. “If you’ve got one parent [with a history], you’ve got probably about a 45 per cent chance of having it; with two sides there’s a much increased chance,” Davey says. This is borne out in the lab: in 2011, researchers who collected DNA from families in Ottawa in Canada concluded there was indeed “a strong genetic basis for this condition” with sleepwalking possibly “transmitted as an autosomal dominant trait” – a strong chance of a child inheriting the disorder from one of their parents.

“My husband and I both [sleepwalked], but we both grew out of it,” says Kristen Lenehan, whose daughter, Charlotte, is seeking help for the condition at the Monash Children’s Hospital after years of escalating sleepwalking and night terrors. Now in her final years of school, Charlotte typically wakes several times a night most nights, screaming or walking around, and recently suffered a serious injury when she tripped over a bedside cabinet, leading to surgery. “That night, she said she just woke up in agony gripping her leg,” says Kristen. “She was terrified. She just had no idea what had happened to her.”

After numerous trips to GPs, who focused on basic sleep hygiene as a cause, Charlotte was eventually referred to Davey at the Monash Children’s clinic and spent a night there. Plugged into machines, her brain signals revealed she was transitioning back out of deep sleep too often, a partial arousal sometimes causing her to sleepwalk. Says her mother: “In the sleep study, even when they couldn’t hear her, sitting outside the room, she was still reacting – sitting up, talking, moving her body around, moving her arms around.“ It is now hoped that the right medication will help Charlotte’s brain stay in deep sleep and not continually pop back out.

What’s going on in the mind of a sleepwalker?

Are sleepwalkers merely responding robotically to unconscious commands or is there something more sophisticated going on? Is the chef who finds themselves whipping up a stir-fry, or the pianist who plays a tune, doing it entirely by rote? Historically, experts have taken the view that because walking occurs outside of REM sleep they couldn’t be dreaming, and because their higher functions are locked into deep sleep no true reasoning could be taking place. Consequently, they call sleepwalkers’ behaviour only “semi-purposeful”.

Sleepwalkers are unreliable witnesses. It’s typical for them to have no recollection of their nocturnal adventures, and if you wake one in the act they are groggy and confused. Still, anecdotally, some of us who walk report dreams, at least of a kind, and can remember vaguely what happened. My experience – sample size of one – suggests at least some walkers believe they are doing something when heading off into the night. Some have reported having dramatic dreams: being chased, being attacked. Wild animals feature occasionally. For others, anxiety is the underlying emotion: having to get something done, to tidy up, to be somewhere else and soon … without necessarily being given the full story.

“Consciousness during episodes appears to be variable, ranging from ... minimal ... to vivid dream-like scenarios.”

US writer Laura Miller, who has recounted her family’s almost comic prevalence of sleepwalking, describes her own nighttime motivation as “depressingly administrative”, finding herself pulling on a coat in the middle of the night over her nightclothes “with the fading conviction that I need to perform some shadowy task right now”. Growing up, she writes, while her somnambulist brother acted out combat and strategy, Miller and her similarly afflicted mother “dreamed of errands”.

Studies are beginning to corroborate this anecdotal reporting. Says Colin Tuft: “It used to be thought that dreams only occurred in REM sleep and that sleep walking was not related to dreams at all. But there’s been smatterings of reports that people do recall some sort of dream.” In 2009, Delphine Oudiette and colleagues affiliated with the Cognitive Neuroscience Lab at Northwestern University in Illinois interviewed 38 self-identified sleepwalkers and most said they did dream during their episodes. “Short, unpleasant dreamlike mentations [brain activities] may occur during sleepwalking/sleep terrors episodes,” the researchers concluded, “suggesting that a complex mental activity takes place during slow wave sleep.”

Another researcher, Francesca Siclari at the Netherlands Institute for Neuroscience, is co-authoring a publication on changes in the brain during parasomnia episodes, when patients are dreaming as opposed to being completely unconscious, “a fascinating opportunity to see what happens when the normally well-defined boundaries between sleep and wakefulness become disrupted,” she says via email. “I started to systematically interview sleepwalkers about their experiences. I realised that the level of consciousness during episodes appears to be variable, ranging from short, mostly automatic behaviours with no or minimal consciousness to behaviours in relation to vivid dream-like scenarios.”

“Sleep isn’t as black and white as some of the traditional teaching will have it.”

There is another theory, near-impossible to prove, that sleepwalkers don’t dream in real time but – Freud would have loved this – retrospectively construct a memory of a dream to rationalise their behaviour. While acknowledging there may be dream behaviour occurring during parasomnias, Colin Tuft also speculates: “Perhaps they just have this partial memory of that sleepwalking event that they’ve conceptualised as a dream.” In other words, you find yourself in the kitchen or on the street or under the bed and your slow-to-wake, higher-reasoning faculties construct a vague story to account for your otherwise unaccountable behaviour, to protect your fragile psyche.

Indeed, “Sleep isn’t as black and white as some of the traditional teaching will have it,” says Kirk Kee, senior sleep physician at the Royal Melbourne Hospital. Until the day comes when we can see into somebody’s head and project their dreams onto a screen, we can only speculate about what is going on in there. Says Kee: “How would we ever know?”

Doing errands in your sleep sounds efficient. What’s the catch?

How great would it be to wake up in the morning to find your house dusted and vacuumed! Sadly, it rarely works out that well. While many sleepwalkers have their eyes open, manage to not bump into things and make it back to bed with no harm done, accounts of those tidying up, rearranging furniture or moving pictures around are rare. Much more common is night eating: gobbling an entire jar of peanut butter or, according to one expert’s report, a sandwich made with two slices of white bread and a squirt of dishwashing liquid. Misadventures of the kind suffered by Kristen Lenehan’s daughter, Charlotte, are not entirely uncommon, either.

A study of 620,000 admissions to a Swiss hospital discovered ... just 11 incidents of treatment for a sleepwalking injury.

In February, an 18-year-old dairy farmer from Victoria sleepwalked out of a first-storey window while staying overnight with friends, waking only after falling some 4.5 metres. “All I recall is being in agony on the ground screaming while rolling around in pain,” she told Nine, owner of this masthead. She was flown to the Alfred Hospital’s trauma unit for surgery on her spine and pelvis. US comedian Mike Birbiglia also believes he jumped out of a window, in 2005, while sleepwalking, but landed on grass and was largely unhurt – an incident he later worked into his stage routine.

A 2013 study that did manage to gather a cohort of some 100 chronic walkers, tie them down in a lab in Montpellier, France, and plug them full of leads concluded that adult sleepwalking “is a potentially serious condition that may induce violent behaviours, self-injury or injury to bed partners, sleep disruption, excessive daytime sleepiness, fatigue, and psychological distress, all of which affect health-related quality of life.” Overall, though, the risk to the general population seems minimal: a 2016 study of 620,000 admissions to a Swiss hospital between 2000 and 2015 discovered just 11 incidents of treatment for a sleepwalking injury, including fractures from falls, concussion, head wounds and cuts.

Have sleepwalkers really driven cars or walked across town?

Some sleepwalkers make it out their front door. I know because I’ve done it, and a parent interviewed for this article said their son had once escaped down the street. More complicated behaviours are much less common. There have been uncorroborated reports of people driving cars or walking long distances but “it’s incredibly rare”, says Colin Tuft. “It’s possible to go outside the house before walking down the street. It’s possible to go further, but I think [driving a car] is really stretching what is plausible, given that we know that you are still partly asleep.”

Associate Professor Darren Mansfield, from the Turner Institute at Monash University, is similarly sceptical, but says it’s possible. “Presumably if you can navigate a doorway, you can open a car door and get in. And because we drive cars as such a daily occurrence, these things can be a little bit automatic,” he says. “Once it needs a little more decision-making that’s when it all comes undone.”

Probably the most famous example of sleep-driving occurred in May 1987 in Ontario, Canada, when Kenneth Parks drove 20 kilometres from his home to that of his in-laws, where he murdered his mother-in-law and tried to choke his father-in-law. He claimed he had been asleep the whole time and in 1991 a jury agreed, finding him not guilty on a defence of “non‑insane automatism”. A court of appeal agreed with the verdict. It noted: “Our system of justice is predicated on the notion that only those who act voluntarily should be punished under the criminal law.”

“Our system of justice is predicated on the notion that only those who act voluntarily should be punished under the criminal law.”

In 1950, in what was reported as the first case of its kind in the English-speaking world, a jury freed a Melbourne mother accused of murdering her daughter, because she claimed to have done it in her sleep. Believing that “soldiers” were invading her house (apparently triggered by reports from the Korean War), she attacked one with an axe only to find it was her daughter she had killed. A psychiatrist told a court the woman had previously been found in the street in her nightclothes and concluded that she suffered from “some form of hysteria”, which included bizarre nighttime behaviour.

More recently, a resident of Coffs Harbour with a history of sleepwalking went to bed, naked, around 10 one night in 2014 after drinking beer with friends and subsequently woke up in a strange house under arrest. He had, apparently, left his own home, found his way into the stranger’s home through their laundry (the other external doors were locked), dressed himself with a child’s cardigan he found there, then attacked a woman he encountered in the house while yelling “aargh”. A judge found him not guilty, saying prosecutors had not disproven the reasonable possibility he was sleepwalking, making his actions involuntary.

Monash University’s Darren Mansfield says he typically builds a picture based on several criteria including a history of sleepwalking and, critically, “there can be no evidence that the behaviour was pre-planned, no evidence that the individual is showing awareness at the time and no evidence that they had a recall of the event.”

Is sleepwalking benign, healthwise, or a symptom of something sinister?

Researchers are just beginning to nibble at suggestions classic sleepwalking could indicate a more serious issue with the brain, such as mental illness, but evidence is thin. In children, just a handful of cases can be linked to other disorders such as epilepsy. Chronic sleepwalkers might benefit from medication such as anti-depressants, says Sydney-based forensic psychiatrist and sleep specialist Robert Kaplan.

Much later in life, a similar but different malady called REM behaviour disorder, or RBD, where sufferers act out their dreams but don’t typically walk around, is arousing interest for its possible links to neurological disorders. It is not, technically, sleepwalking, and it is critical to distinguish between the two, but there are parallels.

“It’s very much been a wake-up call. I’ve become very proactive with my own health.”

Normally, when we dream in REM sleep, our brain disconnects our motor functions so we don’t act out what our active mind is experiencing. But in some people, for reasons yet unknown, this mechanism fails: they might fall out of bed, or thrash around, or kick their legs. This turns out to be a useful warning sign for future risk of Parkinson’s or a similar disorder, says Simon Lewis, professor of cognitive neuroscience at the Brain and Mind Centre at the University of Sydney. “We don’t quite know how Parkinson’s really works,” he says, but it seems increasingly likely this effect on the part of the brain linked to RBD is an early part of its pathology. Because it can take decades for Parkinson’s to emerge, the possibility of an early diagnosis through this sleep disorder could lead to treatments that slow or stop what would otherwise be invisible degeneration.

One of his volunteers is Horst Reiss, a NSW-based optometrist who says he first became aware he moved around in bed while he dreamed about a decade ago – “kicking a football or swinging an arm or something” – and subsequently realised he was a likely candidate for RBD and perhaps, eventually, Parkinson’s, which his father had suffered. “It’s very much been a wake-up call,” he says. “I’ve become very proactive with my own health.”

If you wake a sleepwalker, will it kill them on the spot?

One version of this myth apparently originates in ancient tribal cultures which believed that when you slept your soul left your body, so to wake a sleepwalker would leave them without their soul – and presumably dead. It persists today in a belief that waking a walker might shock them into having a heart attack. But even that seems apocryphal, Michael Salemi, general manager at the California Centre for Sleep Disorders, told Scientific American. “I have not heard of a documented case of someone dying from being woken up.”

Walkers – myself included – can attest that being disrupted from whatever essential task you think you’re performing can be annoying, to say the least.

But it’s not completely cut and dried. Wake a walker and you can expect a muddled, even aggressive reaction. There are examples of court cases where a sleep walker has attacked somebody who’s disturbed them. Margot Davey knows of parents who have intervened in their child’s nocturnal episodes only to receive an unconscious elbow to the ribs or worse. Says Darren Mansfield: “You’re better to try to corral them back to bed rather than grab them by the shoulders and shake them into a full level of wakefulness because, you know, the higher centres of the brain are not awake and as they wake you can sometimes elicit a bit of a violent response.”

Walkers – myself included – can attest that being disrupted from whatever essential task you think you’re performing can be annoying, to say the least. And, a couple of levels of consciousness further up, being discovered sleepwalking is embarrassing, even shameful, so you’re likely to try to deny it. Being woken up, US writer Laura Miller wrote of her experiences in Slate, rarely helps. “What that feels like is this: You’re propelled forward, gliding on the perfect confidence of dream logic, and this naysayer is impeding you, generating friction and snags that threaten to drag you into a befuddled wakefulness. It makes you mad.” So, by all means, gently guide a spooky somnambulist back to bed, if you dare, but take care. They might not thank you for it.

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