Sleep paralysis occurs when the body fails to 'unfreeze' in sync with waking.

Sleepwalking, or somnambulism, is a bit of a misnomer since many things can occur during this state, including speaking, using the bathroom, and more.

People with a sleep disorder called REM Sleep without Atonia don't experience the temporary paralysis of skeletal muscles that typically occurs during REM sleep—instead, they have vivid dreams that they act out during sleep.

Narcolepsy occurs when the brain loses its ability to control its sleep-wake cycle

Narcolepsy not only makes people fall asleep at random moments, but it can also cause hallucinations, insomnia, and sleep paralysis. The disorder is tied to cells in the brain’s hypothalamus called hypocretin, which are neuropeptides responsible for keeping you awake and controlling your dreaming from coming on too quickly.

Why do we sometimes jolt awake before falling asleep?

Around 70% of people are estimated to experience the sensation of falling and jerking awake right as they're about to drift to sleep. That mysterious phenomenon is called hypnic jerking. As common as it is, hypnotic jerking remains disconcerting and hard to explain. While we don't yet have clear answers, peruse this article in Popular Science for some possible explanations as to why this happens.

Sleep apnea explained

While sleep apnea is directly tied to an increased risk of cardiovascular and metabolic health problems, many affected people are unaware of their problem. Sleep apnea occurs when upper airway muscles relax during sleep and pinch off the airway, which can cause breathing to pause for 10 seconds or more at a time. Sleep partners (rather than those inflicted) are often the first to notice breathing pauses or loud snoring in their bedmates.

Sleep is no longer considered a binary state—scientists are seeking to map a variety of liminal states between sleep and waking, including the hypnagogic state associated with boosts of creativity.

Sleep disorders can exacerbate neurological and other health conditions

Brain regions that control sleep sit adjacent to those that regulate the autonomic nervous system, which controls involuntary bodily functions like heart and breathing rates. These neighbors influence each other, meaning poor sleep can impair or negatively impact the ANS, further disturbing sleep.

What it's like to live with insomnia

The biological process Shakespeare referred to as the chief nourisher of life's feast is necessary for the body and mind to rest and repair from the activities of daily life. As sleep evades the exhausted, sufferers also lose emotional stability, mental clarity, social connections, and more while simultaneously gaining waves of interrupted biological processes that can lead to disease and death.

Dreams largely occur during REM sleep (but not entirely).

The body's response to cardiac arrest has been linked to near-death experiences

Most people who report near‑death experiences experience events like out‑of‑body sensations, altered cognition, emotional and spiritual shifts, or even supernatural phenomena, particularly during cardiac arrest. Research suggests many such experiences may be linked to brain-generated sensory distortions that can be experimentally replicated, suggesting a physiological rather than mystical cause.

What happens when we sleep

Sleep is a highly specialized and complex process that begins via signals from a region of the brain called the hypothalamus. As explained in this overview video from The Economist, the hypothalamus maintains our circadian rhythm by using light cues from our environment to regulate sleep via a compound known as melatonin. Once asleep, the brain begins the "sleep cycle" and progresses through the four stages of sleep over and over again each night.

Why do dreamers twitch?

This thought-provoking piece highlights newer research suggesting sleep twitches may not be random dream leftovers, but instead a crucial way our brains map and understand our bodies. From sleeping rat pups to dreaming octopi, this biological mapping system appears universal across animal species.

Panic attacks are intense fear episodes that often occur without a clear trigger

Unlike typical fear responses to real danger, panic attacks can mimic serious health problems, such as heart attacks. Sweating during a panic attack may seem random, but it's a leftover survival mechanism that made it easier for our ancestors to escape by slipping out of an attacker’s grasp.

The brain will attempt to rest itself in periods of chronic sleep deprivation

Skimping on sleep lengthens reaction times and blunts decision-making skills. At a certain point, the brain will try to sneak sleep where it can, shifting sections offline even as you remain awake. Going without sleep raises blood pressure, undermines the immune system, and increases one's risk of dementia.

Ghost stories across cultures often trace back to traumatic events

From a bat-like demon in Tanzania to a malevolent woman figure hovering above your sleeping body, the four disturbing tales outlined in this NPR article offer a glimpse into how happenings from WWII or the Aztec Empire haunt people’s memories.

The deadly genetic disease that steals shut-eye

Few are haunted by fatal familial insomnia. This neurodegenerative disease is typically carried through bloodlines via genetic mutation of the prion protein gene, forcing the body to create abnormal and pathological protein variations that can corrupt normal versions. This article follows a musician as they attempt to come to terms with the FFI plaguing their family (and, possibly, their future).

Nightmares are unpredictable, but are linked to stress, anxiety, trauma, and more.

Music may give some of us the chills and goose bumps—perhaps because it shocks us

The science is still unsettled about why music can trigger a chill down your spine, formally known as frisson, but one theory is that anything surprising to the nervous system—including sudden beat drops or unexpected harmonies—stimulates a type of alarm response that gives rise to this feeling.

The overlooked physical causes of insomnia

Persistent lack of sleep is dangerous for anyone, but women are especially unlikely to have their symptoms taken seriously. This article highlights the physical causes of insomnia—a condition often written off as solely psychological—and the importance of early diagnosis. The writer, Courtney Maum, was diagnosed with an anterior nasal valve collapse as the source of her insomnia.

Cerebrospinal fluid flushes waste from your brain during sleep

Recent research suggests a nightly brain cleanup as an important purpose of sleep. Brain waves have been observed to work in lockstep with the brain’s blood flow and cerebrospinal fluid flow, allowing for a cleansing tide that washes away toxic waste.

Sleeping on a problem does seem to help—in fact research published in 2026 suggests scientists can seed people's dreams with sound cues about a difficult puzzle during REM sleep and they'll be better able to solve it.

'1440 Explores' Episode 3: Why We See Ghosts and What Isn't There

Every culture has them—restless spirits, haunted houses, things that go bump in the night. But why do we believe in ghosts? Psychologist and skeptic Dr. Chris French joins host Sony Kassam to explore the science behind the supernatural, from sleep paralysis and hallucinations to the brain's pattern-making instincts. Together, they uncover why our minds see meaning—and sometimes ghosts—where none exist, and what that reveals about fear, memory, and our need to believe in something beyond the grave.

Why don’t you remember all your dreams?

Despite being a near-nightly occurrence, we remember very few of our dreams. Researchers believe reduced activity in regions where memories are stored, a different neurochemical environment during sleep, and rapid transition during waking contribute to this phenomenon.

Sleep deprivation may slow metabolism

This article explains that, according to research from Penn State, restricting sleep for just a few days can affect how the human body metabolizes fats and change how satisfied people feel after a meal. The study found that people who don’t get...

The body's sleep-wake cycle is one of its many circadian rhythms

The body's sleep-wake cycle is one of its many circadian rhythms, which are behaviors or biological processes that exhibit 24-hour patterns. These rhythms are deeply impacted by light exposure, food availability, and much more, meaning where you live impacts your sleep.

How seizures (potentially) alter consciousness

Seizures occur when intense electrical activity floods the brain, prompting significant loss of self-control and a variety of sensory disruptions and hallucinations. Cultures interpret the episodes differently, with many contemporary norms viewing them as negative while others characterize them as intense spiritual occasions. Author Fyodor Dostoyevsky viewed his seizures this way, as well as cultures in Mongolia, some Shamanic indigenous religions, and others.

Explore a series of bedtime exercises to improve sleep

Low-impact, mindful movements can potentially help the body and mind relax before sleeping. Such exercises could be a helpful complement to regular exercise during the day.

Paralysis from polio occurs in under 1% of infections

About 1 in 200 cases of infection causes paralysis. For paralysis to occur, the virus travels from the throat, intestines, and gut to infect specific cells within the spinal cord and brain stem that control movements. Within hours of invading the nervous system, paralysis can occur. The virus can be present in bodily secretions and stool for multiple weeks post-infection.

A deep dive into how a body decomposes

Dead bodies are, understandably, scary and unsettling. Learn about the fascinating process of decomposition that takes place in every human, and how its teeming with life.

Forty to 110 minutes of deep sleep is recommended per night

Adults typically spend 10% to 20% of the night in deep sleep, also known as slow-wave sleep, with the rest of the night spent either in light sleep or REM states.

Falling into a black hole would stretch and shred your body beyond recognition

As you approach a black hole, you initially feel weightless. Eventually, the difference in gravity between your feet and head would create a powerful stretching force that overcomes the molecular bonds in your body and pulls you apart.

Learn how a doctor successfully treated a patient's phantom limb pain with a mirror, tricking his brain into thinking his still-present arm was the missing paralyzed left one.

How to end bedtime procrastination

Finally done with external obligations, you might plop onto the sofa and dive into a hobby or bit of media, pushing past sleepiness to have some time to yourself and enjoy doing what you want. This is known as "revenge bedtime procrastination," a behavior that feels relaxing but impairs sleep hygiene.

The side effects of falling back and springing forward

Daylight saving time can interfere with a person’s sleep schedule, but it also has been linked to increased rates of depression, heart attack, stroke, cancer, and car accidents. UT Southwestern’s Dr. Joseph Takahashi explains why the time change is bad for your brain and health.

The lost medieval habit of 'two sleeps'

While most people accept a single seven-to-nine-hour nightly slumber is ideal, the approach is a relatively modern idea. For centuries, interrupted sleep was the norm, with historians uncovering descriptions of two periods of sleep during the normal 24-hour cycle.

Fearology, or the study of fear, explores the difference between stress and fear

Our brains involuntarily respond to our environment and signal alarm when that isn’t always needed, triggering responses that include goose bumps. But understanding fear and how to talk our brains into calming down can improve daily life.

Why do you shiver when cold?

Humans are warm-blooded creatures, so our bodies like to maintain internal temperatures separate from and typically above those in their environment. This is made possible by a process known as thermoregulation. When the brain's hypothalamus senses a drop in the body's core temperature, skeletal muscles may be ordered to shiver, sending out waves of muscle contractions and exothermic biochemical reactions whose byproduct includes heat and energy.

How does the body know where it is in space?

Close your eyes and touch your nose. How did you know where your nose was? How could you tell where your hand was? That's proprioception, the sense that keeps your brain apprised of the body's position and movement. This article explains how this sense works, what happens when people don't have it, and what we know about it.

Why don't humans hibernate?

Hibernation is a superpower in the animal world that allows certain species to time travel from difficult times to abundance. This essay in Aeon explains this helpful natural process and why humanity's technological advancements may have hindered our ability to participate in the practice. Learn about the rising interest in human hibernation as a result of modern adversity, and if it could potentially become a reality.

Schizophrenia literally means 'split mind'—a reference to patients' break with reality

Contrary to the name, patients do not have multiple personalities. Rather, the split mind refers to the sufferers' inability to distinguish reality from hallucinations when they are aware and awake. Cognitive difficulties, including challenges focusing and communicating are also common among those with schizophrenia, as well as auditory and visual hallucinations.

Why 'spacing out' or dissociating may help reduce trauma awareness

Dissociation may have developed as a defense mechanism in the brain to help navigate intense emotional or physical situations by providing out-of-body experiences that put distance between the mind and the environment. However, in about 1.1% and 1.5% percent of the general population, a severe form of this separation can produce alternate identities, or alters.

BPPV occurs when tiny calcium particles called otoconia become dislodged

WIth this condition, formally known as benign paroxysmal positional vertigo, calcium particles that normally help the brain interpret head movement and position migrate for unknown reasons into the ear's semicircular canals, sending irregular nerve impulses to the brain, which cause intense vertigo episodes.

Slenderman is the most infamous example of creepypasta

In 2014, two teens playing in the woods at the edge of a suburban park turned on their third friend, stabbing her 19 times in an attack they claimed was compelled by Slenderman, a meme-turned-urban legend.

Folk horror involves remote settings and ancient traditions

Folk horror often features outsiders venturing to isolated areas and finding the locals engaged in disturbing (often occult) traditions. Rather than using supernatural elements, the horror often comes from the locals themselves. Examples include the 1973 film “The Wicker Man” and Shirley Jackson’s 1948 short story “The Lottery”.

What is space sickness?

Mix motion sickness minus gravity with a host of other variables, and you’ve got a recipe for space adaptation syndrome. It can hit anyone, even astronauts who escaped the issue previously. This article details the history and science behind space sickness.

Partial freezing results from trying to freeze water while preventing expansion

Within a sealed container, partial freezing of water increases the contained volume and the pressure, preventing further freezing without decreasing the temperature further. Once cooled below -23 degrees Celsius (-9.4 degrees Fahrenheit), an uncommon type of ice that contracts as it forms is produced, facilitating the complete freezing of the contained water.

An intense fear must persist for at least six months to be diagnosed as a phobia

Research suggests that both environmental and genetic factors can contribute to the onset of these intense, irrational fears. Often, they can stem from an early traumatic experience, but not always.

The second phase of acute stress: the 'slow' response

The body's reaction to acute stress involves two responses: fast and slow. The first occurs immediately, with the central nervous system triggering the release of adrenaline. The second releases cortisol, which elevates blood sugar and blood pressure and restricts nonessential functions like digestion and the immune system.

Christians believe Jesus was resurrected, body and all

The Christian doctrine of bodily resurrection—that Jesus rose physically, not as a ghost or spirit, and that believers will do the same at the end of time—was found absurd by ancient Greeks. Plato preferred a disembodied soul escaping the body. Paul, on the other hand, staked the entire faith on it. Theologians describe the resurrected body as the same body, but as a transformed one.

Brain death is a uniquely modern problem stemming from modern ventilators

Patients who would have once died from devastating brain injury can now live on a ventilator for a long period of time, creating ethical, medical, and legal dilemmas.