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Dreams have captivated humanity for millennia, interpreted as divine omens in ancient cultures or as Freudian insights into unconscious desires. Modern neuroscience explores dreams as a window into consciousness because they provide a naturally occurring altered state where the brain generates complex, internally-driven experiences.

However, to study dreams people need to remember them, and it’s not well understood what is involved in dream recall or why some people seem to remember them better than others. A new study, published in Communications Psychology, investigated the factors associated with remembering dreams in 217 healthy people aged 19-70 years who recorded their dreams every morning for 15 days while their sleep and cognitive data were tracked by wearable devices and psychometric tests.

“Dreams represent an important model for understanding how consciousness emerges in the brain,” said Giulio Bernardi, MD, PhD, professor of psychology at IMT School for Advanced Studies Lucca in Lucca, Italy, and senior author of the study. “We know that we forget most of our dreams, and so we wanted to understand why there is this difference between different people because these are factors that are important for us in the study of consciousness.”

Sleep progresses through several stages during the night: N1 is light sleep; N2 is deeper sleep; N3 is the deepest sleep, also called slow-wave sleep; and rapid eye movement (REM) sleep is most associated with dreaming. These patterns cycle throughout the night.

“Within REM sleep, we usually have more vivid dreams, more perceptual dreams, and this means that these dreams are easier to remember,” explained Valentina Elce, PhD, postdoctoral researcher in Bernardi’s lab and lead author of the study.

Their data indicates that people who had longer, lighter sleep tended to at least remember that they dreamed — these people may have had more REM sleep. Younger people remembered more dream details than older people. Also, participants reported less dream recall during winter than during spring, suggesting environmental or circadian influences.

Additionally, people who remembered more dreams tended to be people who daydreamed as well. “This propensity of the brain to generate spontaneous experiences goes beyond sleep and also affects mental activity during the day,” Elce explained.

Interestingly, people who said they didn’t remember their dreams at the beginning of the study reported that they were able to remember more by the end of the study, Elce said. This indicates that the process of intentionally trying to remember and record dreams can help people remember them.

“This study had several strong points, including the longitudinal collection and the large, diverse sample size. The amount of data gathered about each participant was also impressive, ranging from physiological measurements to psychological testing,” noted Caleb Lack, PhD, psychology professor at the University of Central Oklahoma, Edmond, Oklahoma, who was not involved in the study. A weakness of the study, he said, was that all study participants were from Italy, and there may be some cultural differences in dream recall.

Based on the study’s findings, dream recall seems to be a result of a combination of factors like sleep conditions, thinking about dreams in the morning, and mind wandering during the day, Lack noted. “In other words, both individual traits and your environment play a role in whether or not you remember any dreams,” he said. “Overall, [the results] are pretty in line with prior findings and expectations based on factors we know influence whether or not you recall having dreamed.”

Why we dream is still a mystery. “The scientific community does not agree yet about the potential biological function of dreams, and one of the possible ideas is that dreams help us to consolidate our memories…but also to elaborate the emotional content of our experiences,” Elce said.

“A huge body of work has shown that our dreams are heavily influenced by what we are thinking about and what stimuli we encounter while awake,” Lack said. But psychologists no longer believe, like Freud did, that the content of our dreams has great significance in our daily lives.

“However, it’s true that the state of your mental health can impact your dream content — for instance, being highly stressed can lead to more negative emotions in your dreams, or traumatic events can cause nightmares. If that’s happening, addressing those difficulties is best done through evidence-based psychotherapies,” Lack said.

Lack noted that cognitive-behavioral therapy has been shown to improve quality of sleep and lower nightmares in those with anxiety disorders.

But if someone rarely or never remembers dreaming, it’s nothing to worry about. “The majority of people remember few to no dreams they had the prior night, although prior research shows we probably have around 2 hours of them a night, although there is pretty wide variation in this from person to person as seen in the study,” Lack said. 

Elce and Bernardi hope their study will help in other research. They gave an example of a study that sought to test whether dreaming helped performance in a task. It enrolled 22 people but only four people remembered dreaming about the task, so the study couldn’t draw strong conclusions. Having tools to help people remember their dreams could help in similar future studies.

“Understanding what happens to the healthy sleeping brain is something crucial,” Elce noted. This study, Lack said, “sets the stage for further understanding into just why certain people remember more of their dreams, as well as suggesting some ways to help people remember more of their dreams, if that’s something they want to do.”

Next, Bernardi hopes to look at dream content and eventually to “see how dreams change in pathological conditions to see whether maybe dreams could be used as an index, as a marker of some alterations in the brain,” he explained. He wants to know if diseases like dementia or Alzheimer’s lead to changes in dreaming, which could be helpful for diagnosis.