New study uncovers how poor sleep sets the stage for nightmares—but not the other way around

A new study published in the Journal of Sleep Research offers insight into how disrupted sleep and nightmares are related. Using wearable technology to track sleep patterns in the homes of participants, researchers found that nights with disturbed sleep tended to be followed by nightmares—but nightmares themselves didn’t make future sleep worse. The findings suggest that trouble staying asleep may create the conditions that make nightmares more likely, rather than nightmares causing insomnia in the short term.

The study was designed to explore whether nightmares and insomnia influence each other over time. Previous research has shown strong associations between nightmares and mental health problems such as anxiety, depression, and even suicidal thoughts. However, scientists are still working to understand the everyday factors that lead to the appearance of nightmares. One promising theory suggests that sleep disruptions—such as waking up frequently during the night—may increase emotional vulnerability, making people more likely to experience disturbing dreams. This study aimed to test that theory in a natural sleep setting, using both brainwave data and daily self-reports to track when and how nightmares occur.

To test these ideas, researchers recruited 61 adult participants living in the United States. Each participant wore a device called the DREEM 3 headband while they slept at home over a two-week period. This device uses sensors to measure brain activity and provides detailed data about sleep structure, including how long a person spends in different stages of sleep. Participants also completed surveys each morning and evening, reporting on their sleep quality, how refreshed they felt, and any dreams they remembered. These reports were reviewed by trained raters, who categorized them based on whether the dream qualified as a nightmare. A dream was labeled as a nightmare if it included themes like fear, physical danger, or other threatening content—especially if it caused the person to wake up.

The researchers specifically focused on a sleep measure called “wake after sleep onset,” which refers to how long a person spends awake during the night after initially falling asleep. This is a standard way to track sleep disturbance and is often used as an indicator of insomnia. They also measured time spent in deep sleep, known as N3 sleep, which is thought to be important for physical restoration and emotional recovery.

The researchers found that nightmares tended to occur on nights that followed particularly restless sleep. If a participant experienced more frequent or prolonged awakenings one night, they were significantly more likely to have a nightmare the next night. However, sleep quality on the same night as the nightmare, or two nights before, did not seem to have the same effect. This pattern suggests that disturbed sleep may make people more emotionally sensitive or vulnerable during the next night’s sleep, which could increase the chance of having a nightmare.

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Interestingly, the reverse did not hold true. Having a nightmare did not significantly increase sleep disturbance that night or over the following two nights. In other words, while poor sleep appeared to precede nightmares, nightmares did not immediately lead to worse sleep. However, people who reported more nightmares overall across the two-week period did tend to experience higher levels of sleep disruption in general. This suggests that people who are prone to nightmares may also be more likely to have chronic sleep difficulties, even if a single nightmare doesn’t worsen sleep on its own.

The researchers also discovered something unexpected about the connection between nightmares and deep sleep. They found that the percentage of time spent in N3 sleep was actually higher on nights when nightmares occurred. This might seem counterintuitive, since N3 sleep is usually considered the most restorative stage of sleep.

However, the authors suggest that this may reflect a kind of rebound effect. After a night of poor sleep, the brain may attempt to compensate by spending more time in deep sleep the following night. This rebound might coincide with the emotional intensity that gives rise to nightmares. In other words, nightmares might be more likely to occur during nights when the body is trying to catch up on restorative sleep following a period of disturbance.

This idea is supported by additional findings in the study. When researchers looked at the interaction between previous-night sleep disturbance and current-night deep sleep, they found that the effect of poor sleep on nightmare likelihood was strongest when it was followed by a night of relatively undisturbed sleep. This means that it might not be just poor sleep or just deep sleep that triggers nightmares—but a particular sequence of the two.

Another important aspect of the study was the use of both objective and subjective data. Participants reported how well they thought they slept each night, but these ratings did not predict whether they would have a nightmare. This disconnect between how people feel about their sleep and what actually happens during the night has been found in earlier studies as well. It points to the value of using physiological data to track sleep patterns and understand the factors that lead to nightmares.

Despite these findings, the study does have some limitations. The sample size was relatively small, and participants were responsible for wearing and managing the sleep headbands at home. Although the devices were previously validated against gold-standard sleep studies, the accuracy of data can still vary due to device placement and signal quality. Also, the classification of nightmares relied on subjective dream reports, which means that nights without remembered dreams were not included. This could lead to some underestimation of nightmare frequency.

Future research could build on this study by using laboratory settings to wake participants during specific stages of sleep and ask them about their dreams in real time. It may also be helpful to investigate whether different types of sleep disturbance have different effects on dream content. Additionally, the study did not measure nightmare distress, which is a separate construct from frequency and may be more closely tied to subjective sleep quality.

The study, “The association between sleep disturbance and nightmares: Temporal dynamics of nightmare occurrence and sleep architecture in the home,” was authored by John Balch, Rachel Raider, Chanel Reed, and Patrick McNamara.