What Causes Nightmares, and How Can You Lessen Them?

falling off a cliff — One study showed that dreaming of falling is the most common type of nightmare. Klaus Vedfelt/Getty Images

By day, Lisa (last name withheld) in Charleston, South Carolina has it all together: a solid marriage, beautiful kids, thriving career. By night, however, the beauty fades and something more sinister takes over. Lisa suffers from chronic, unpredictably spaced nightmares and has for decades. "Sometimes I will have multiple per night. Sometimes I will go two or three weeks without [one]," she explains in an email interview.

Lisa isn't visited by the second coming of Freddy Krueger or anything like that, but the content of these terrible dreams is still pretty jarring. In one recurring nightmare, she's driving too fast through a notorious Atlanta highway interchange known as "Spaghetti Junction," and goes off the edge, crashing to her death. "It goes through my mind that I know I am doing it and everyone is going to be so disappointed in me," she says.

Another example has her hunting down a demon in her mother-in-law's house. "I have to work hard to climb and get to the demon, who is deep within the house, but with each dream I get closer," she recalls. "The most recent one, I was looking through a knot in the wood door and he was looking back at me, eye to eye. It was horrible."

Everyone has the occasional nightmare. Roughly 5 percent of the general population has at least one bad dream per week, says clinical psychologist and sleep expert Dr. Michael Breus in an email interview. "Nightmares typically happen during REM sleep, during the middle and later portions of the night," he explains. "Because of where nightmares tend to fall in the sleep cycle, and because of the intensity of their imagery and emotions, nightmares will result in some degree of awakening. You may bolt upright in bed and have trouble returning to sleep, thanks to a nightmare."

We don't know exactly why nightmares happen, but Breus says it's possible that they help the brain, "practice, prepare for and even anticipate difficult or dangerous experiences in waking life." In fact, often such issues need attention in daylight hours, so it's possible that Lisa lives in fear of a highway crash or needs to talk some things over with her mother-in-law. "Of course it's possible that nightmares, like dreams in general, don't have a primary function — that they're a byproduct of other activities in the body," says Breus. "But most sleep scientists think that dreams and nightmares exist for some purpose."

One study found the most common nightmare was falling, followed by dreams of being chased, of dying, feeling lost, and feeling trapped.

Causes of Nightmares

Certain circumstances and characteristics make some people more prone to nightmares than others, says Savannah, Georgia-based internist and sleep medicine specialist Dr. Barry Krakow, author of the forthcoming book "Life Saving Sleep," which delves deeply into nightmares and other sleep disorders. People who've been traumatized are certainly at higher risk of nightmares, he says, offering examples like war veterans, those who've suffered sexual or criminal assault, or those who have been in a life-threatening accident. People with some degree of sensitivity in their biological makeup are also more likely to have bad dreams, so they're more common in people who suffer from anxiety or depression, or who use excess opiate drugs or alcohol.

Folklore often attributes nightmares to eating too much rich food before bedtime, but the jury is out on whether this is true. One study from 2015 did find a link between eating dairy or spicy foods before bedtime and having disturbing dreams, but the study authors noted that this couldn't be proven conclusively because the data was self-reported and there were a lot of other variables to consider. (For instance, some of the participants were binge eaters, practiced intermittent fasting and or may have had undiagnosed reactions to certain foods.)

However, research in recent decades has shown that people who suffer from sleep disorders are also more likely to have nightmares. Specifically, people with undiagnosed or untreated sleep apnea are at higher risk, Krakow explains.

Dreaming of ghosts or monsters is also a fairly common nightmare.
David Wall/Getty Images

The Link Between Nightmares and Sleep Apnea

People with sleep apnea stop and then start breathing again hundreds of times throughout the night. Although it is largely associated with snoring, a person doesn't have to snore to have sleep apnea. People with sleep apnea are generally very tired during the day, even when they've supposedly slept all through the night. Other symptoms of sleep apnea are gasping for air while sleeping, dry mouth or headache in the morning, problems staying asleep, irritability and attention issues.

According to Krakow, the many misconceptions regarding sleep apnea make it tough for a person to get diagnosed. "So many children have sleep apnea and they don't get diagnosed until they're 50 years old," he says. This is a big deal because in addition to nightmares, sleep apnea is associated with greater risk of diabetes, brain dysfunction, heart disease and so on. "There are so many deaths caused over the course of time by oxygen not getting to the brain," he explains.

His practice currently helps to treat mental health patients with sleep disorders. "So many of these have undiagnosed sleep apnea," he says, noting that they've seen thousands of patients at his center with nightmares. "The vast majority report reducing sleep apnea by using a CPAP machine, which then appeared to decrease nightmares." Formally known as continuous positive airway pressure (CPAP) therapy, this is a standard treatment for people with obstructive sleep apnea.

The problem is that many mental health professionals, whom people typically approach for help with nightmares, are not aware of the sleep apnea link. "Some people go into psychotherapy for years for PTSD and the nightmares don't go away," Dr. Krakow laments.

Using Imagery Rehearsal Therapy to Treat Nightmares

Even nightmare sufferers who don't have sleep apnea have another option, though. Way back in 2001, Krakow and his team published a groundbreaking study in JAMA. The study pioneered "imagery rehearsal therapy," or IRT, which the team describes as a brief treatment that reduces chronic nightmares, improves overall sleep quality and reduces the symptoms of PTSD. The problem is, even though the treatment is endorsed by the American Sleep Academy and has been studied by dozens of groups around the world, many health professionals don't know about it.

Here's how it works: "You teach somebody how to picture a new version of your dream in your mind's eye while you're awake, and that has a very powerful impact over your dreams," Krakow says, noting that it only takes a couple of weeks to see clear-cut decreases in nightmares. "By picturing new images they seem to be activating an imaging system that sets into motion the process of decreasing disturbing dreams."

The study showed dramatic results: "Posttraumatic stress symptoms decreased by at least 1 level of clinical severity in 65 percent of the treatment group compared with symptoms worsening or not changing in 69 percent of controls," the study authors wrote. Krakow notes that IRT is "just as powerful as somebody using a PTSD medication."

For many, it's not even technically necessary to visit a professional to engage in IRT, although some people might be better off. "It is very simple and very effective, but sometimes people would do better to do the technique with a therapist," he says.