I think dreams are endlessly fascinating. They’re one of sleep’s great mysteries—even to sleep experts and sleep scientists.
Why are dreams and nightmares so interesting to us? In their strangeness and emotional intensity, they have the power to capture our imagination. And yet, we really don’t know all that much about the purpose of dreaming. Scientists continue to work to understand the underlying biological purpose behind dreams. (There are some scientists who think it’s possible dreaming has no purpose, but most scientists who study sleep and dreams think that dreams serve a function.
We all dream—whether we remember them the next morning or not. And we’ve all had the experience of a nightmare that leaves us rattled and shaken (and relieved to be awake) the next morning. Nightmares are just as much of a mystery as every other type of dream. But we’re learning more all the time about what might cause them, what they might signal, and what they could mean.
Your dreams might be a rehearsal for real-life frights
One theory of dreaming that could explain some of the scary and strange aspects of our dreams, is known as the “threat simulation theory” of dreaming. This theory suggests that our brains have evolved to use dreams as a way to rehearse, or simulate, circumstances that could pose danger to us in waking life. In the threat simulation theory, our dreams aren’t only a chance to practice taking action to protect ourselves in dangerous situations. Our dreams are also an opportunity to explore the emotional and psychological terrain associated with threat and fear.
Scientific studies have returned mixed results on this dream theory. There’s a body of research that gives support to this theory, with findings that show threats are a common element to dreams, and that we’re often taking evasive or defensive action when facing down threats in our dreams. A 2006 study collected more than 200 dream reports, and found about two-thirds of dreams contained at least one threat. This study also found that dreamers tended to take sensible and reasonable actions to evade dream threats, suggesting these dreams might be a form of mental rehearsal. But in this same study, researchers found only a small number of dreams—fewer than 15 percent—contained realistic situations that people might find threatening in their waking lives.
One aspect of the threat simulation theory is the hypothesis that people who live in conditions or circumstances where their physical and emotional safety are threatened will use dreams more frequently to practice responding to threats. Some research has supported this hypothesis, including a 2005 study that compared the dreams of traumatized Kurdish children to non-traumatized Finnish children. Scientists found the kids who’d experienced trauma reported dreaming more frequently than children who had not experienced trauma. The traumatized children also reported having a higher number of threatening events in their dreams, as well as more severely threatening events, compared to non-traumatized children.
Other research has undercut this theory, including a 2008 study that found people who lived in a high-crime area actually experienced fewer threatening dreams than people who lived in a low-crime area.
Whether or not we use dreams specifically to rehearse our response to threats, there is evidence showing dreams are vehicle for our brains to solve problems connected to waking life. In 2010, a group of scientists tested a theory of problem-solving in dreams by teaching a group of 99 volunteers a maze puzzle, then testing them on the maze several hours later—after some of the volunteers had taken a nap. Scientists found that the nappers who dreamed about the maze performed better on the maze puzzle than nappers who didn’t dream, or volunteers who didn’t nap at all.
Dreams of teeth falling out might be related to dental problems
Have you ever had a dream that your teeth fell out? For many people, teeth dreams are some of the oddest, most puzzling dream subjects. Teeth dreams have been a mystery and a fascination throughout human history. The ancient Greeks tried to divine meaning behind teeth-falling-out dreams, speculating that they had to do with unpaid debts. Other cultures have associated teeth-falling out dreams with foretellings of death.
Fast forward to modern life, and scientists continue to wonder about the significance of dream content—including dreams related to teeth. Teeth dreams are very common: one recent study found that more than 39 percent of participants had experienced a teeth-related dream at least once in their lives. In a new study released in 2018, Israeli scientists investigated a couple of theories about teeth dreams. Analyzing the sleep and dreams of more than 200 undergraduate college students, the researchers investigated:
- Whether teeth dreams are a sign of psychological distress
- If teeth dreams are a response to physical symptoms of dental irritation
They found no relation between teeth dreams and psychological distress in their subjects. They did find, however, that other disturbing and common dream subjects, including falling and being smothered, were linked to psychological pain. Other research has found a connection between teeth-loss dreams and mental distress, with people who dream of losing teeth more likely to be anxious, depressed, feeling more helpless and less in control.
But on the issue of dental pain? Scientists did find a link with teeth dreams. Specifically, tension in the mouth related to teeth grinding was associated with the dreams related to teeth. If your teeth are falling out in your dreams, it might be time for a trip to the dentist!
Sleep paralysis is connected to ‘waking dreams’
The phrase itself—sleep paralysis—is pretty scary-sounding. The experience of sleep paralysis is often terrifying, especially the first time a person experiences it. What is sleep paralysis? It’s what’s known as a parasomnia, or an unpleasant, unwelcome sleep phenomenon. To say sleep paralysis is unwelcome and unpleasant is something of an understatement. This is a highly disruptive, frightening parasomnia that typically occurs when a person is falling into sleep or waking up from sleep, and finds themselves unable to move or speak.
Sleep paralysis isn’t dangerous. But it can be very frightening. Often (though not always) sleep paralysis is accompanied by waking nightmares. There are frightening hallucinations that happen when we’re in a state of waking consciousness. Research shows that waking nightmares that happen with sleep paralysis often have similar themes. In episodes of sleep paralysis, people often will:
- Feel the presence of an evil being or spirit
- See or feel a dangerous intruder looming over them, or coming toward them
- Feel physically threatened
- Feel as though they are being choked or smothered
Sleep paralysis isn’t uncommon. Estimates vary, but recent research suggests that more than 7 percent of the general population experience sleep paralysis at some point in their lifetime. People with mental health conditions are at higher risk for sleep paralysis. Research shows that more than 30 percent of psychiatric patients experience sleep paralysis during their lifetime, along with nearly 35 percent of people with panic disorder.
Isolated or occasional episodes of sleep paralysis are relatively common. If you experience sleep paralysis on a regular basis, or if sleep paralysis creates significant anxiety for you (including anxiety about falling asleep), talk with your doctor about your experiences.
Dreaming of being smothered may relate to respiratory problems
Dreams of being smothered or choked are another common—and really scary—subject of nightmares. They’re also another dream subject that scientists have examined for a connection to our physical health, as well as to our psychological state of mind.
Sensations of being choked or smothered are often part of the waking dreams that happen to people who experience sleep paralysis. Research has also found links between psychological distress and nightmares that involve choking or smothering.
The scientific investigations about whether choking or smothering dreams are related to a person’s actual breathing are pretty interesting, and also not conclusive. Some studies have found smothering and choking dreams happen more often among people who experience pauses in breathing during sleep. These breathing pauses, known as apneas, are a hallmark symptom of obstructive sleep apnea. But other studies have found that people with OSA don’t dream about being choked or smothered any more often than people without OSA.
The quality of our breathing while we’re awake also might affect the frequency of frightening choking dreams. The same study that found people with OSA aren’t more likely to dream about being smothered, also found that people who experience breathing problems while awake DO dream more often of being choked or smothered, compared to people without waking respiratory distress.
There’s a lot about dreaming that deserves more scientific attention—and this relationship to disrupted breathing is one particular area I’d really like to see investigated further. Sleep-disordered breathing, including sleep apnea, is an enormous health problem that too often goes undiagnosed. Could our dreams be one signal of an undetected breathing condition? I’d like to know.
Many physicians don’t know a lot about nightmares and dreams
This recent finding is a little scary to me. A 2018 study by a team of scientists from the University of Kansas and the University of Tulsa found that medical practitioners in the U.S. are under-informed about nightmares, and lack experience in addressing nightmares and other sleep problems in their patients. Seventy percent of the clinicians who participated in the study reported having no experience dealing with nightmares, while 78 percent had inaccurate information about nightmares.
The same study found doctors under-informed about sleep disorders. More than three-quarters of the physicians thought sleep disorders were a “secondary problem”—a symptom of another condition—rather than a condition in their own right. Sleep disorders such as insomnia can arise as a result of other conditions. But millions of Americans suffer from primary insomnia and other sleep disorders that aren’t just a symptom of another problem.
This study highlights the importance of working with a trained, experienced sleep specialist on your sleep issues, whether they be nightmares or anything else sleep-related. If you have concerns about your sleep (including disruptive dreams) seek out the help of a board-certified sleep clinician—especially if you’ve brought your sleep issues to your primary care doctor’s attention and aren’t getting the advice and help you need to sleep better. You can find an American Academy of Sleep Medicine certified sleep center near you, here.
I hope you dream and sleep well this Halloween week!
Michael J. Breus, PhD, DABSM
The Sleep Doctor