Bringing Nightmares to Light

You're being chased by a shadowy creature. You can’t get a good look at it, but it’s terrifying—and out to get you. The next minute, you’re falling through the sky. But just before you hit the ground with a SPLAT, you jerk awake. Thank goodness: It was just a nightmare!

Your body doesn’t completely shut down when you sleep. As you rest, your brain is still hard at work, making connections, cataloguing information, and storing memories from the day. The result of all that activity is dreams. “Dreams are our brain thinking in a very different state,” says Deirdre Barrett, a psychologist at Harvard Medical School in Massachusetts. “During sleep, the areas of the brain associated with imagination, emotions, and storytelling are turned up high, while our logic is turned way down."

A shadowy creature is chasing you. You can’t get a good look at it, but it’s terrifying—and out to get you. The next minute, you’re falling through the sky. You’re about to hit the ground with a SPLAT, but you jerk awake. Thank goodness: It was just a nightmare!

Your body doesn’t completely shut down when you sleep. As you rest, your brain is still hard at work. It makes connections, sorts information, and stores memories from the day. All that activity results in dreams. “Dreams are our brain thinking in a very different state,” says Deirdre Barrett, a psychologist at Harvard Medical School in Massachusetts. “During sleep, the areas of the brain associated with imagination, emotions, and storytelling are turned up high, while our logic is turned way down.”  

Dreams are often nonsensical and strange. Sometimes, they can also be downright scary. Nightmares are frightening dreams that cause people to wake up from sleep. Although about 85 percent of adults report having occasional nightmares, only 5 percent have frequent nightmares. These distressing dreams are even more common in kids and teens. Although nightmares are a completely normal part of life, they’re not well-understood by scientists. That’s why researchers are coming up with new techniques to help take the scare out of nightmares.

Dreams are often strange, and they don’t make sense. And sometimes, they can be downright scary. Nightmares are terrifying dreams that wake people from sleep. About 85 percent of adults report having nightmares at times, but only 5 percent have frequent nightmares. These upsetting dreams are even more common in kids and teens. Nightmares are a completely normal part of life. But scientists don’t understand them well. That’s why researchers are finding new ways to help take the scare out of nightmares. 

As we doze, our bodies move through different stages, collectively known as the sleep cycle (see The Sleep Cycle). Dreams can occur anytime during the night. But the most vivid ones—including most nightmares—happen when we enter rapid eye movement (REM) sleep. During this stage in the sleep cycle, a person’s eyes quickly shift back and forth beneath their eyelids, and brain activity increases.

Scientists think that REM sleep is important for processing recent experiences and storing memories. That could be why worries from the waking world often show up in bad dreams. Nightmares also appear to be more common in people dealing with a lot of anxiety. Barrett investigated the influence of stress from the Covid-19 pandemic on people’s dreams, for example. “People would dream about getting Covid,” she says. They also reported dreams about bug attacks or lurking invisible monsters—both likely symbolic representations of the virus. When people had to quarantine, often cut off from friends and family, some even dreamed about going to prison or living alone on Mars, Barrett adds (see Interpreting Nightmares).

As we sleep, our bodies move through different stages. Together, these stages are known as the sleep cycle (see The Sleep Cycle). Dreams can happen anytime during the night. But the most powerful ones, including most nightmares, happen in rapid eye movement (REM) sleep. During this stage, a person’s eyes quickly move back and forth beneath their eyelids. Brain activity also increases.

Scientists think that REM sleep is important. It may help process recent experiences and store memories. That could be why bad dreams often contain worries from the waking world. And when people deal with a lot of anxiety, they seem to have more nightmares. Barrett studied how stress from the Covid-19 pandemic affects people’s dreams, for example. “People would dream about getting Covid,” she says. They also reported dreams about bug attacks or hidden invisible monsters. Both likely stood for the virus. When people had to quarantine, they were often cut off from friends and family. Then some of them dreamed about going to prison or living alone on Mars, Barrett adds (see Interpreting Nightmares). 

For a long time, the only way for scientists to investigate nightmares has been through personal reports. Subjects usually explain their dreams verbally or write them down in a dream journal. But researchers are now testing new technologies that allow them to observe the sleeping brain more directly.

One of these methods, called functional magnetic resonance imaging (fMRI), measures activity in different parts of the brain. Recently, scientists at the University of Geneva in Switzerland took fMRI scans of volunteers’ brains to gauge their emotions while looking at distressing images, like a person being attacked. Scientists observed less intense brain activity in people who experienced more frequent nightmares. This led scientists to hypothesize that the purpose of nightmares might be to help prepare people to deal with frightening situations in the real world.

For a long time, scientists have had only one way to study nightmares. It’s through personal reports. Subjects usually talk about their dreams or write them down in a dream journal. But with new technologies, researchers can observe the sleeping brain more directly. They’re now testing these methods.

One of these methods is functional magnetic resonance imaging (fMRI). It measures activity in different parts of the brain. Recently, scientists at the University of Geneva in Switzerland did a study. Volunteers looked at upsetting images, like a person being attacked. At the same time, scientists took fMRI scans of the volunteers’ brains to measure their emotions. Scientists found less intense brain activity in people who had more frequent nightmares. This led scientists to an idea about the purpose of nightmares. The dreams might help prepare people to deal with scary situations in the real world. 

In another study, scientists at Kyoto University in Japan used fMRI technology to record people’s brains as they pictured different symbols, like shapes or letters. Then the researchers recorded the subjects’ brain activity while asleep. When participants awoke, they described what they had seen in their dreams. The scientists fed both the brain scans and dream imagery into a neural network, a computer program that mimics the way a human brain operates to make connections between different pieces of information. The program used the data to generate rough re-creations of what people were visualizing while dreaming. It eventually learned to do this based only on data from their brain scans. One day, this technology could help nightmare sufferers better understand the content of their dreams, which may help make them less scary.

Scientists at Kyoto University in Japan used fMRI technology in another study. They recorded people’s brains as they pictured different symbols, like shapes or letters. Then they recorded the subjects’ brain activity while asleep. When subjects awoke, they described what they had seen in their dreams. The scientists fed both the brain scans and dream images into a neural network. This computer program imitates the way a human brain makes connections between different pieces of information. The program used the data to make rough re-creations of what people saw in their dreams. Over time, it learned to do this with only data from their brain scans. One day, this technology could help nightmare sufferers understand the content of their dreams better. And that may help make the dreams less scary.

Some scientists want to go beyond interpreting dreams. They want to influence what people are dreaming about, a technique called dream engineering. “Controlling dreams can be good if you’re trying to direct people away from nightmares,” says Adam Haar Horowitz. He’s a Ph.D. student at the Massachusetts Institute of Technology studying mindfulness and mind-wandering. Horowitz is working on a device called Dormio, which prompts people to dream about specific subjects. Participants wear a sensor glove that tracks changes in muscle activity, while an audio recording asks them targeted questions, guiding their dreams as they fall asleep.

Other scientists are studying a technology called transcranial stimulation to manipulate dreams. Electrodes painlessly pass an electrical current through the brain. This activates certain parts of the sleeping brain and can trigger lucid dreaming—a state where a person is aware they are dreaming. Knowing they are seeing and feeling something that isn’t real could help take the fear out of a nightmare.

Some scientists want to do more than explain dreams. They want to affect what people dream about. This is called dream engineering. “Controlling dreams can be good if you’re trying to direct people away from nightmares,” says Adam Haar Horowitz, a Ph.D. student at the Massachusetts Institute of Technology. He studies mindfulness and mind-wandering. Horowitz is working on a device called Dormio. It prompts people to dream about certain subjects. People wear a sensor glove that tracks changes in muscle activity, and an audio recording asks them targeted questions. It guides their dreams as they fall asleep.

Other scientists are studying a technology called transcranial stimulation to affect dreams. Electrodes painlessly pass an electrical current through the brain. This activates certain parts of the sleeping brain. It can trigger lucid dreaming—a state where people know they are dreaming. They know they are seeing and feeling something that isn’t real. And that could help take the fear out of a nightmare.