Extreme conditions do some pretty weird things to the brain. Here, in order of increasing severity, we look at 10 hostile environments and the unsettling hallucinations each has provoked during prolonged exposure.
10. Space
You’d think the novelty of space flight would keep the mind from distraction and fantasy. But hallucinations are common. Described by an ISS astronaut in 2012 as “luminous dancing fairies,” spontaneous and intrusive flashes and streaks of light have been reported since the earliest Apollo missions. Although this little-known nuisance can be ignored during work hours, it can interfere with getting to sleep. Only recently has the cause been identified. Without an atmosphere to absorb cosmic rays from distant supernovae, “free-moving subatomic particles” pass through the skull and trigger optical nerve cells.
But other types of hallucination have also been reported. In 1976, the crew of the Salyut-5 space station were urgently brought back to Earth when they reported a smell that suggested a fluid leak. The replacement crew, equipped with special breathing equipment, immediately upon arrival realized the smell was imagined. The olfactory hallucination was attributed to stress and a breakdown of relations between crew members.
9. Prison
Some of the most hostile environments on Earth are manmade. Prisoners in solitary confinement often experience vivid hallucinations. It’s so common it has a nickname: “the prisoner’s cinema.” It’s a “blind screen of hallucinations” that “forms itself on the eyes” when “cut off from visual stimuli.”
In the 1950s and ’60s, the US and Canadian governments were enthused by the idea of using this phenomenon to brainwash their prisoners. At Montreal’s McGill University Medical Center, researchers paid college students to spend days in sensorily deprived isolation. Not only did they have to wear translucent visors to minimize visual input, but they also had to listen to the continuous white noise hum of air conditioning units, while laying on foam pillows and wearing cotton gloves, as well as cardboard cuffs that extended beyond the reach of the fingertips, to limit tactile sensations. Within hours, the students were struggling—not least from hallucinations. These began as “points of light, lines or shapes,” then developed into vivid, often bizarre scenes, like a procession of squirrels with sacks over their shoulders or eyeglasses filing down a street. There were auditory hallucinations as well, including the sound of a music box, as well as tactile hallucinations, such as the feeling of being shot in the arm. Even after the students were freed, they continued to hallucinate—for example, that the room was moving or changing in shape.
8. Mountains
Although commonly explained as altitude sickness, there’s something eerily paranormal about the so-called ‘third man’ hallucinations of mountaineers.
In 2008, Jeremy Windsor was climbing Everest alone and had reached “the Balcony” (a “cold windswept snow shelf [26,900 feet] high up on the southeast ridge” when he heard a muffled hello. Behind him—though not clearly, through his oxygen mask—he saw another climber, who introduced himself to Windsor as Jimmy. For the next 10 hours, the two climbed together, exchanging words of encouragement. Although he didn’t keep sight of him, and in fact didn’t see him again, he was always aware of his presence. He heard Jimmy’s crampons scraping on the ice, the flow of oxygen into his mask, and also felt his weight on the safety line they shared. Then, when they reached the Hillary Step, the final ridge before the summit, Jimmy said “cheerio” and disappeared.
Such encounters are often reported by mountaineers who climb to high altitudes. Since they’re associated with the “death zone” altitude, it’s thought they may be a survival mechanism. Another mountaineer saw not one but two people coming towards him as he descended a mountain exhausted and lost. It was night-time, so he only saw the flashlights—accompanied by a sense of salvation. This lasted three hours. Although he was confused by never actually reaching these people, the hope kept him going. And they only disappeared when he finally found his tent.
7. Underwater
Also known as the “rapture of the deep,” nitrogen narcosis occurs when pressurized nitrogen enters the bloodstream. It affects the central nervous system of divers descending beyond recreational depths, causing disorientation, confusion, euphoria, and, sometimes, hallucinations.
It’s especially common in freediving, “the only sport” as one diver put it “where athletes get intoxicated during the most crucial part of their performance.” Experienced divers call it being “narcked.” One recalls seeing imaginary colors in the absence of anything else to focus on, and how closing his eyes created a pixellated visual effect. More bizarrely, he’s had something like an out-of-body experience, seeing himself descending from a third-person perspective. Other divers have reported fractal patterns, as well as figures and faces.
Although it’s a reversible condition, it can impair a diver’s ability to recognize the need to resurface—which is especially problematic when diving alone. But hallucinations can also cause problems in communication between divers. One scuba diver remembers writing something in plain English on his slate only for a diving buddy to look at it and shrug his shoulders, indicating he didn’t understand. Only when they got back to the surface did the diver who wrote the message realize that what he thought was in English was actually “gobbledygook.”
6. Jungle
In 1981, the Israeli adventurer Yossi Ghinsberg spent three weeks lost in the Amazon—having set out looking for gold. His ordeal was reproduced in the 2017 movie Jungle, but it couldn’t quite capture his anguish. As he put it, “usually movies are bigger than life. This movie is smaller than life.” Not only did it lack the budget and time to show everything, it could never show Ghinsberg’s inner feelings.
In addition to crippling hunger, tree-felling storms, and skin-burrowing insects, he was also entirely alone once he got separated from his companion, Kevin. At night, he hallucinated the other man’s voice desperately calling his name. But the most terrifying vision came on Day 5 while hiding from a half-imagined jaguar. From the darkness, he saw Kevin emerge and look disapprovingly at what remained of the food. “You should share, Yossi,” he whispered before he got angry. “There isn’t enough food for both of us. So you thought you were going to make it out of here without me?” Then Kevin grinned, lifting the machete and bringing it down upon Ghinsberg. At this, he snapped back to reality.
5. Desert island
When Leendert Hasenboch, a soldier for the Dutch East India Company, was marooned on an island for being gay, he kept a journal of his mental decline. After the first month, he began to hallucinate. He was, he said, haunted by “devilish spirits”—one of which resembled a man he was “well acquainted with” but afraid to mention by name. Assuming he was being punished for his “sins,” Hasenboch prayed for forgiveness.
It’s not clear what happened to him after his journal entries stopped. The last things he wrote about were having to drink his urine and eat raw flesh. Despite there being two freshwater sources on the island, he evidently didn’t find either. When another of the company’s ships came to pick him up, they found only his camp and belongings. There was no body or skeleton, leading some to believe he was rescued.
4. Caves and mines
It’s easy to lose track of reality after days trapped in a cave underground. French caver Michel Siffre deliberately isolated himself in this way to see what would happen to his mind—particularly his sense of time passing. Without any indication of daylight, he said, he was unable to tell the difference between a normal sleep cycle and the 48-hour cycle he fell into—spending 36 hours awake and the other 12 asleep without thinking anything was amiss. Things only get worse as time goes on. Prolonged darkness deprives the brain of the light it needs for the essential neurotransmitters norepinephrine, dopamine, and serotonin—leading to despair and psychosis. Hallucinations begin within hours.
Les Hewitt, a caver who once spent a night in a cave, listening as it flooded with water, remembers hallucinating and contemplating suicide. “If I’d had a gun,” he said, “I would have shot myself.” In 1963, two coal miners trapped underground in Pennsylvania experienced beatific visions of Heaven. At some point during their two weeks of darkness, they said, they were suddenly bathed in light and watched as a door opened to a marble staircase and a celestial city of angels. They also saw the recently deceased Pope John XXIII smiling down on them.
3. Desert
Antoine de Saint-Exupéry, one of the most famous people ever to be stranded in the desert, spent four days wandering when his plane crashed in Libya. His book The Little Prince, which draws on his experience, is the second most translated in history (after the Bible). During this time, he and his mechanic-navigator had a day’s worth of fluids to drink—much of which was coffee and wine. Hopelessly lost in the featureless terrain, Saint-Exupéry said he “had simply turned to sand and was a being without mind.” He saw not only the usual mirages (optical illusions of water, prompting him to walk with his eyes to the ground), but also strange hallucinations, including encounters with imaginary creatures, phantom processions of lamps, and the sight of dogs chasing each other. He also imagined he was on a ship for South America, a slave, looking up at the mast swaying to and fro against the starry night sky.
In the desert, one factor contributing to hallucinations is heatstroke. Another can be the lack of sleep. One competitor in the Gobi Desert ultramarathon recalls losing his mind just 30 kilometers (out of 250, and in first place) from the finish line. Having slept for just one hour the night before, he suddenly forgot why he was running; it just became his default setting, inexplicably. He called his wife for a reality check and was able to regain his sanity, but after 45 minutes he lost it again. “It was only me around,” he said, “nothing to anchor me, I was spinning out of control.”
2. Antarctica
In the 1890s, a Belgian whaling ship called Belgica got stuck in Antarctic sea ice, trapping the crew for more than a year. Afraid to lose sight of the ship, they mostly stayed on board—which, though it was sensible, only hastened their mental unspooling. As the ship’s medic noted, “murder, suicide, starvation, insanity, icy death and all the acts of the devil [became] regular mental pictures.”
When summer finally came, the crew’s hopes of the ice melting just enough to let them sail free—hopes they had clung to through the winter—were suddenly dashed. After that, psychotic symptoms got worse. One man questioned whether he was really on the Belgica at all; he had no memory of boarding. He also became suspicious of his crewmates, believing they wanted to kill him, and spent most of his time in hiding. Paranoid delusions of violence are curiously typical of isolation in Antarctica—so much so that in 1928 American explorer Richard Byrd planned to bring two coffins and 12 straitjackets on his expedition to the continent. As recently as 2018, one scientist stabbed another in the chest (for spoiling the endings of books).
“Polar madness” is attributed to several factors, including the disruption of circadian rhythm, confinement, and conflicts. Humans aren’t adapted to live in such conditions, and even polar natives are affected. The Inughuit of Greenland call it pibloktoq.
Another common delusion is the ‘third man syndrome’, where imaginary expeditioners are hallucinated. Sometimes, though, hallucinations are just silly. British Antarctic explorer Felicity Aston, on her solo trip across the continent, said she was haunted by the smell of fish and chips. “It drove me insane,” she said. “It was like I was skiing along a huge row of fish and chip shops, the whole day.”
1. Sea
During 14 months lost at sea, adrift on a small fishing boat, 36-year-old fisherman José Salvador Alvarenga was swept 6,700 miles from Mexico. During this time, he drank his urine, learned to catch fish in his hands, swallowed whole jellyfish, designed a rainwater collection system, and scavenged what he could from floating trash bags (including food and used chewing gum). Tragically, he also watched his crewmate die in his arms. After two months, the other fisherman, Ezequiel Córdoba, succumbed to thirst and sickness from eating raw seabirds. But Alvarenga was so desperate and lonely that he kept the corpse aboard for a week, talking to it, as well as for it in reply. When he finally let it go into the water, he fainted.
As his boat drifted further out to sea, his ordeal was only beginning. He saw plenty of ships but none saw him; most were freighters with no crew on deck. To compensate for this new isolation, he abandoned himself to his imagination. In the mornings, he’d walk around the deck imagining he was “wandering the world.” And he would intentionally hallucinate imaginary friends and family. So vivid were these hallucinations that he would later say that he “tasted the greatest meals of his life and experienced the most delicious sex” during this time. When he finally reached land—the southernmost of the Marshall Islands, thousands of miles from any other shoreline—he assumed he was hallucinating again. But he just about made it ashore and was lucky enough to find a couple who rescued him.
He’s far from alone in experiencing hallucinations during prolonged time at sea. Joshua Slocum, the first person to sail around the world on his own, saw Martín Alonso Pinzón—a captain from Christopher Columbus’s first voyage to the New World—on board his boat. Another circumnavigator, Bernard Moitessier, came out on deck to see a man looking at him before criticizing him for sitting around “scratching his arse.” Others have hallucinated not even being at sea, like former navy diver Rob Hewitt, who before he was rescued from the water had imagined he wandered ashore to buy a can of coke.