Your bedmate is whimpering in their sleep and perhaps thrashing about. It looks like a nightmare. Should you wake them?
Nope, experts say. As terrible as whatever visions that are running through their head might be, waking someone from a nightmare is more likely to ensure that they’ll remember the bad dream. And if someone appears physically distressed in their sleep like this, it’s more likely that they’re having a night terror than a nightmare; night terrors are different neurological experiences.
Nightmares are a normal part of dreaming, says Deirdre Barrett, a dream researcher at Harvard Medical School and author of The Committee of Sleep (Oneiroi Press, 2001). They almost always happen in rapid eye movement (REM) sleep, the stage of sleep marked by brain activity that looks very similar to that of an awake brain.
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“Except for being scary, they look like every other dream,” Barrett says.
During REM sleep, the brain areas responsible for long-term memory storage show altered activation, so people don’t tend to remember their nightmares unless those sleep tales are scary enough to wake them up. Once a dreamer awakens, their long-term memory regions come back on line. Most of the time, someone having a nightmare will be indistinguishable from a peaceful dreamer. During a nightmare, heart rate increases by seven beats per minute on average, says Michael Schredl, a dream and sleep researcher at the Central Institute of Mental Health in Germany. Otherwise the sleeper typically lies still in bed: during REM sleep, muscles are paralyzed, which keeps people from acting out their dreams.
If someone is moving around, talking in their sleep or sleepwalking while appearing distressed, it’s more likely a night terror, which occurs during non-REM sleep, Schredl says.
Night terrors are particularly common among kids, says Leslie Ellis, a clinical counselor in British Columbia who treats patients with nightmares. “You shouldn’t wake them up because they’ll be disoriented,” Ellis says. “They won’t have any recollection of the episode if you don’t wake them up.”
Nightmares can be echoes of the stressful experiences people are having in their waking hours. During the early days of the COVID pandemic, people reported more nightmares, according to several studies on the topic. New themes also emerged, according to research published in the journal Somnologie in 2022, including those about sickness, confinement and bugs—the latter subject is perhaps a symbol of infection or contamination.
People also sometimes seemed to be working through the new rules of the pandemic, says Anu-Katriina Pesonen, a psychological researcher at the University of Helsinki, who documented dream changes that occurred in early 2020. “The dreams were often reexperiences of new behavioral rules,” Pesonen says. “For example, hand shaking in a dream was vividly experienced as a major mistake. This could assist in learning new norms.”
The occasional scary dream is nothing to worry about, but frequent nightmares can sometimes be part of a larger psychological disorder. The good news, Barrett and Ellis say, is that these nightmares are remarkably treatable. The people who have the most trouble with nightmares, Barrett says, have often experienced trauma. They may relive their traumatic experiences, sometimes with the addition of even darker fears. These nightmares are often so alarming that they interrupt the person’s healing.
“I’ve never heard anyone say they don’t mind having PTSD [post-traumatic stress disorder] nightmares much. They say things like, ‘It’s like having the trauma happen again, night after night,’” Barrett says.
Some of these trauma-related nightmares can occur outside of REM sleep, Barrett says, suggesting that they’re more like PTSD flashbacks than like regular dreams. Waking someone from these nightmares isn’t a long-term solution, but people having them can be coached to take control of the dreams. There are different ways to do this. Some psychologists and counselors will simply talk a person through possible alternative endings for a nightmare. This can be anything from a magical rescue to the person saving themselves. In her practice, Ellis has patients relax into a sort of daydream where they rewrite the circumstances of the bad dream while making sure they feel safe and comfortable.
In a 2020 meta-analysis of studies, researchers found that this treatment, called “imagery rehearsal therapy,” was likely as effective as medications for ending post-traumatic nightmares. Anecdotally, the method can also work for repeated nightmares, or bad dreams that recur, sometimes for years.
“I’ve worked with people who had the same dream for decades, but now the dream is different, or sometimes it doesn’t come back,” Ellis says.
It’s possible to try imagery rehearsal therapy on yourself, Ellis says. But, she adds, if your nightmares are particularly persistent or distressing, or if they’re the result of trauma, it’s best to seek professional help.