It’s four in the morning and you wake from a dream. It wasn’t a nightmare exactly, but it was vivid and unsettling—a circus of imagery in which the other commuters stuck in gridlock beside you were all octopi or your feet were transformed into a pair of horse hooves while going through airport security.
Maybe you don’t often remember your dreams but this one, this episode that fused the mundane with the outlandish, it sticks. Even days later, you can still see those tentacles gripping the s
It’s four in the morning and you wake from a dream. It wasn’t a nightmare exactly, but it was vivid and unsettling—a circus of imagery in which the other commuters stuck in gridlock beside you were all octopi or your feet were transformed into a pair of horse hooves while going through airport security.
Maybe you don’t often remember your dreams but this one, this episode that fused the mundane with the outlandish, it sticks. Even days later, you can still see those tentacles gripping the steering wheels or feel the awkwardness of your gait running to catch your flight.
It couldn’t have been that joint you smoked before bed, could it? Science says maybe.
How weed effects sleep cycles
Reports of vivid dreams are “very well known” in cannabis and neuroscience research, says Andrew Kesner, assistant professor of psychology at Indiana University in Indianapolis. But “we still don’t really know the neurobiology of dreaming and what sort of features make you remember your dreams better or worse.”
Cannabinoids are found naturally in the brain in a non-psychoactive form called endocannabinoids. Endocannabinoids control our sleep/wake cycle, aka our circadian rhythms, by modulating and maintaining the brain’s biological balance through an abundant receptors neuroscientists call CB1.
“When people fall asleep, the brain makes its own cannabinoids that increase and decrease throughout the sleep-wake cycle, and throughout the day,” explains Kesner.
Marijuana contains a different form of cannabinoid than the one naturally produced by the brain, THC or tetrahydrocannabinol. THC also works on the brain’s CB1 receptors but, unlike endocannabinoids, it is psychoactive, meaning it makes users feel high by producing feelings like euphoria and paranoia.
Blooming cannabis plant ready to be harvested into various THC-based products. Image: Sunan Wongsa-nga / Getty Images Sunan Wongsa-nga
When you smoke weed before bed, the THC added to the brain’s natural endocannabinoids sends the brain’s CB1 receptors into overdrive. And when those CB1 receptors are in overdrive, they change the way you sleep.
Natural sleep in healthy adults begins with a short period of nodding off followed by a stage of “slow-wave” sleep, that deep sleep from which it’s hard to wake someone up. Cycles of lighter sleep punctuated by bouts of REM (rapid eye movement) sleep follow, growing longer and longer throughout the night.
“REM sleep is classically the time when you’re dreaming,” says Kesner, when “your brain acts like it’s awake but the brain stem paralyzes your body so you can’t act out your dreams.”
Consuming THC appears to suppress REM sleep: It causes it to arrive later in the sleep cycle and to make up less of the overall percentage of sleep. THC also causes more frequent interruptions to REM sleep. That, says Kesner, may be the origins of its reputation for causing weird dreams.
“We know if you wake someone up in REM sleep, that’s when they have the highest chance to remember their dreams,” he explains. So, while there’s no evidence that dreams under the influence of THC are any different than THC-free dreams, the ability to remember them more easily may make the sleeper believe they are more bizarre or intense.
“It’s possible that the THC could be making dreams more intense by changing cortical activity [the way the brain functions], making them wonkier and maybe adding some variability to what you’re dreaming about,” Kesner continues. But the huge variability among individuals in both sleep and the effects of THC use makes objectively studying weed-induced dreams “kind of a nightmare”—pun not intended.
Researchers still don’t even know exactly what dreams are or why they happen—though there’s a good chance that it may be the brain coming up with different learning scenarios, according to Kesner. Someone who plays with puppies all day may, for example, dream that night about being chased by wolves. That way, if it ever happens in real life, the dreamer is better prepared to react to them.
Whether the weed was smoked or taken in edible form is probably also important; THC immediately affects the brain when smoking while edibles take time for the body to metabolize. One study in which participants reported weird dreams after smoking weed before bedtime, therefore, may have had to do more with the way REM sleep “rebounds,” or immediately returns to longer and more robust natural cycles, when the brain experiences THC withdrawal than with THC’s psychoactive effects.
It’s well documented, says Kesner, that chronic THC users experience more intense REM sleep after they stop using it. The same might happen in occasional users, whose REM sleep could theoretically become more intense as the acute effects of weed wears off during the night. In other words, you don’t sleep as well while weed’s psychoactive THC is bouncing around your brain but it becomes much more restorative as soon as its effects wear off.
Ultimately, there probably is no “one-size-fits-all for what cannabis does to sleep or how it affects dreams,” Kesner concludes. As of now, there’s simply not enough data to come to any meaningful verdict. THC or not, dreams are, by their very nature, weird.
In Ask Us Anything, Popular Science answers your most outlandish, mind-burning questions, from the everyday things you’ve always wondered to the bizarre things you never thought to ask. Have something you’ve always wanted to know? Ask us.
The practice of freediving is teaching physiologists how humans stretch their physical and mental limits, which in turn may improve treatments for lung and heart ailments.
The practice of freediving is teaching physiologists how humans stretch their physical and mental limits, which in turn may improve treatments for lung and heart ailments.
Your immune system has one job: to protect you. And most of the time, it does that job like a pro.
But occasionally it gets a bit overzealous, even paranoid. It mistakes harmless, even wonderful things—flowers, peanuts, cats—for threats, and attacks them (and you—mostly you) with a senseless, chaotic vengeance.
For most allergy sufferers, this might mean giving up a few tasty foods, staying inside during high pollen counts, or rehoming the cat—or, more realistically, the person allergic t
Your immune system has one job: to protect you. And most of the time, it does that job like a pro.
But occasionally it gets a bit overzealous, even paranoid. It mistakes harmless, even wonderful things—flowers, peanuts, cats—for threats, and attacks them (and you—mostly you) with a senseless, chaotic vengeance.
For most allergy sufferers, this might mean giving up a few tasty foods, staying inside during high pollen counts, or rehoming the cat—or, more realistically, the person allergic to the cat. But for a tiny number of people, the immune system decides to take aim at one of the most essential substances on earth: water.
Yes, it is possible to be allergic to water. And the condition is even stranger than it sounds.
“Imagine not being able to go into the pool, or the lake, or the ocean,” says dermatologist Dr. Amir Bajoghli, who has treated a patient with this rare condition. “My patient also has to take much faster showers, as you might imagine. It definitely interferes with quality of life.”
Yes, you can be allergic to water
The medical term for an allergy to water is aquagenic urticaria, a form of hives. The condition is so rare that only an estimated 100 to 150 cases have ever been reported. However, researchers believe many more cases go undiagnosed: When a patient comes in complaining of hives, “it could be water” is probably not the first thing that leaps to mind.
People with this rare condition break out in hives like these when exposed to water. Image: Getty Images / Yuliia Kokosha
“Honestly, a lot of general physicians aren’t even aware of it,” says Bajohgli, an adjunct professor at Georgetown University School of Medicine. “It’s rare, and it’s not on their radar.”
Although scientists don’t fully understand exactly how aquagenic urticaria works, they believe water itself isn’t the culprit. Rather, it appears that certain people’s skin responds differently to water contact, setting off a reaction in the skin’s outermost layer. This triggers the body’s mast cells (immune cells that sound the alarm during allergic reactions), which releases histamine, the troublemaking chemical responsible for allergic responses.
Within minutes of water touching the skin, a person with aquagenic urticaria will develop raised, intensely itchy welts. The reaction typically lasts anywhere from 30 minutes to an hour, and the longer the exposure, the more severe the symptoms.
You can still drink water, but sweating can be a problem
Interestingly, and luckily, aquagenic urticaria does not interfere with the body’s need for life-sustaining hydration. In other words, drinking water is fine. When water is swallowed and processed by the gut rather than absorbed through the skin, it doesn’t trigger the same immune response, Bajoghli says.
“The gut, just like the skin and the lungs, is one of the first forms of defense,” he says, “but in this case, somehow, it’s not eliciting the response in the gut the way it does in the skin.”
Bajoghli notes that some patients with aquagenic urticaria do react to their own sweat, although his patient does not. Sweat, he explains, involves an entirely different biological process than external water making contact with the skin.
Scientists believe an unidentified substance in the skin may be triggering this reaction, although much remains unknown.
“It’s still, medically, for us, a mystery,” he says.
How to test if you’re allergic to water
For better or worse (mostly better), water is inescapable. Because of its ubiquity, and also because aquagenic urticaria is something of a medical unicorn, it often takes a while for patients or doctors to connect the dots.
Once it occurs to the patient and provider that water could be the culprit, diagnostic testing is fairly straightforward. It typically involves applying water-soaked compresses to the skin and waiting. In most positive cases, symptoms appear within five minutes, although the test can take up to 30.
“We wait 30 minutes before we call it negative,” Bajoghli says.
The importance of very quick showers
So, what is life like for a person whose body treats H₂O as a sworn enemy? For Bajoghli’s patient, an active teenager involved in sports, the condition reshapes even the most basic daily routines. Among other things, this means really fast showers.
“When he showers for about two minutes, the symptoms are more subdued and milder in nature,” Bajoghli says. “If he takes a longer shower, they’re more severe and they persist longer.”
The good news is that aquagenic urticaria is unlikely to cause a major allergic reaction. It is, however, chronic; patients should not expect it to resolve on its own.
Treatment options do exist, however. Bajoghli’s patient takes an antihistamine called cyproheptadine, which reduces symptoms enough to make that two-minute shower manageable. Timing is important: taking the antihistamine about an hour before water exposure helps maximize its effectiveness.
For patients who need more relief, Bajoghli says a newer drug called omalizumab has shown promise.
For now, the mechanisms behind aquagenic urticaria, including the identity of the substance—or antigen—that triggers it, remain poorly understood, and that knowledge gap makes it difficult to develop more targeted treatments.
“We’re really looking forward to finding out what that antigen is,” Bajoghli says, “and hopefully one day solving this.”
In Ask Us Anything, Popular Science answers your most outlandish, mind-burning questions, from the everyday things you’ve always wondered to the bizarre things you never thought to ask. Have something you’ve always wanted to know? Ask us.
EXCLUSIVE: A slew of international deals for Best Medicine have closed. Sky has scored UK rights for its channels and NOW streaming service, marking a kind of homecoming for the show, which is based on the hit British drama Doc Martin. We also have news of a raft of other deals for the show, which […]
EXCLUSIVE: A slew of international deals for Best Medicine have closed. Sky has scored UK rights for its channels and NOW streaming service, marking a kind of homecoming for the show, which is based on the hit British drama Doc Martin. We also have news of a raft of other deals for the show, which […]
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