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

Stress and anxiety may lead to similar symptoms, but stress is a response to external triggers, while anxiety is persistent, and its symptoms won't disappear once an immediate stressor is gone.

What do your dreams mean, according to science

Humans have been interpreting dreams as signs from deities, spirits, or the psyche for ages, and research shows that reflecting on and analyzing one's dreams can be beneficial. In alignment with dreams' elusive nature, they have no objective or clearly assigned meaning. However, variations of common dreams, such as a surprise exam in a forgotten class, are rife with shared primal fears.

Dream interpretation has evolved from ancient mystical explanations, to dream reports, to tracking electrical activity in the brain and more.

How do anxiety and stress differ?

This article explains that though “stress” and “anxiety” are often used interchangeably, there are distinct differences between the two. Stress is defined as the body's response to an external trigger and can be classified as acute or chronic. Anxiety, however, tends to be triggered internally by excessive thoughts and judgement. Whereas stress disappears when the trigger is gone, anxiety tends to stick around. If left unchecked, both can escalate into more severe mental health conditions.

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.

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

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

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.

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.

We dream for around two hours each night, on average, but the exact purposes of dreams remains under investigation.

An estimated 1 in 250 people—a small subset of the population—reports they've never remembered a single dream.

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

The study of dreams, formally called oneirology, has evolved over the centuries, from anecdotal interpretations to advanced brain imaging.

The dreaming brain, as understood by scientists

Technology has advanced to where the seemingly separate fields of psychology and neuroscience are asking the same questions about dreams, such as whether they're more closely related to perception or visualization. Some field-intersecting findings include research that shows people with impaired face perception don't dream of faces, those with brain legion-related cognition difficulties deal with similar issues in dreams, and children's dreams change in parallel to their cognitive development.

A framework for the various potential causes of insomnia

Insomnia typically occurs in people dealing with life stressors and physical or mental health conditions, though the exact cause continues to elude researchers. Generally, the factors can be broken down into external (such as stress, medication, etc.) or internal (neurological) factors.

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.

Dreams have long been used for religious and political power.

NDEs typically change people's outlooks drastically and can prompt depression

The phenomena are regularly categorized as hallucinations, but some specialists are interested in their psychological nuances. Many survivors report feeling less anxiety about death, though some surveys show the experiences can increase physiological sensitivities.

The REM cycle—named for the 'Rapid Eye Movement' that occurs during this stage of intense dreaming—happens around four to six times per night.

For most of recorded history dreams were considered divine in origin.

Apophenia, the cognitive bias that leads people to find meaning in randomness, helps explain why humans look for meaning in their dreams and even in their tea leaves.

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.

Anxiety is one of the world's most common mental health disorders, causing persistent excessive fear and worry that interferes with daily activities.

During dream sleep, the brain connects new information learned during the day with information already stored in the mind, creating a revised mind-wide web of associations.

The benefits of lucid dreaming

Lucid dreams happen when the dreamer knows they've stepped out of the bounds of waking life. Studies show it can help dreamers cultivate creativity, process grief, and work through trauma. A 2021 study found that 85% of participants with PTSD no longer qualified for the diagnosis after a week of trauma-informed lucid dreaming in which they intentionally witnessed (and therefore integrated) recurring nightmares or changed the outcome completely.

'Those who dream by day are cognizant of many things which escape those who dream only by night.'

- Edgar Allan Poe (1809-1849) in "Elenora"

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

Why are humans hooked on horror?

A haunted horror attraction in Denmark is regularly stalked by researchers of the world's only laboratory dedicated to understanding fear's good side. Fear is one of many human emotions that correspond to a physiological response. As fear rises, so do adrenaline, cortisol, and heart and breath rates. As it ebbs, the body is flooded with dopamine, a hormone and neurotransmitter associated with desire, learning, and motivation.

Literary theorists distinguish between ‘terror’ and ‘horror’

In her essay “On the Supernatural in Poetry,” gothic novelist Ann Radcliffe defined “terror” as the lurking, unseen specter in a story—something that defined gothic literature. “Horror,” on the other hand, was the explicit portrayal of it. For her, the former was artistic, while the latter was cheap.

Scientists are learning to guide your dreams using sound and touch.

Anxiety can arise at any stage of life and make someone feel unsafe in their mind and body.

Visualizing how we dream via Google search trends

When dreams perplex us, we often want to understand them—and in the age of Google, millions go to its search engine to find answers. Now, researchers have compiled a decade's worth of dream-related queries to glean dream trends across seven languages. See what dream was most commonly searched in Arabic in 2015, or what fears and hopes are specific to one culture and time alone with this unique visual essay.

Dreaming under the Nazi Regime

Days after Hitler seized power, a man told psychoanalyst Charlotte Beradt that he had dreamed of being forced to raise his arm in a Nazi salute ("It took me half an hour to get my arm up, inch by inch"). Beradt recorded this dream and many others so they "might one day serve as evidence." This is an English translation of her work, "The Third Reich of Dreams."

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.

Famed psychologist Sigmund Freud believed dreams were symbolic expressions of desire.

Stress activates the "fight-or-flight" response when we face threats, a reaction that can help keep us alive.

A near-death experience is a phenomenon experienced by roughly 5% to 23% of the population, and typically occurs after a traumatic physical event or a brief clinical death.

Horror stories often rely on tropes

All literary genres use tropes, a word used to describe established plot devices, character types, and themes. Horror has many of them, like the "Creepy Child" and the "Evil Mask." Some are based on folklore, like the "Deal with the Devil."

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.

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.

The main criticism of a recent neurophysiological explanation for near-death experiences is that these events are too complex to be explained as a neurochemical response to an oxygen-deprived brain.

Your brain moves through four distinct sleep stages every night

Each stage plays a key role in memory, repair, restoration, and other key biological functions. The full cycle generally proceeds from light sleep and deep rest into vivid REM dreaming, which repeats between three and five times nightly.

Where do phobias come from?

Scientists say phobias are extreme version of a primitive evolutionary mechanism that tells us when danger is near or we are in a dangerous situation. A number of brain regions work in concert to trigger flight or fight responses, and with some...

Researchers say that the horror genre offers opportunities to safely experiment with fear.

Sleep research indicates dogs likely dream about their toys, food, and owners.

A quick technical overview of insomnia

Insomnia is one of the world's most common sleep disorders. Characterized by difficulties falling and staying asleep, long-term struggles with insomnia can prelude or contribute to health difficulties. Treatments range from sleep hygiene management and relaxation therapy, and medication, including antidepressants and melatonin.

How dreams affect your memory

In 1999, scientists conducted a study in which participants were asked to recall images flashed before them for milliseconds. They found that participants who slept before recalling the information performed better than those who had been asked to recall the same information that same day. This was some of the earliest convincing evidence of how crucial sleep is for learning and memory, findings that current research continues to strengthen.

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.

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.

There's a new (contested) physiological explanation for near-death experiences based on analysis of the brains of resuscitated coma and cardiac arrest patients.