Why humans dream remains one of behavioral science's great unanswered questions. Dreams have a purpose but it may not be to send us messages about self-improvement or the future, as many believe. Instead, many researchers now believe that dreaming mediates memory consolidation and mood regulation, a process a little like overnight therapy. But it's not a benefit all share equally: People who are sleep deprived also tend to be dream deprived, spending less time dreaming and perhaps not remembering dreams as well.
Dreams are the stories the brain tells during the REM (rapid eye movement) stage of sleep. People typically have multiple dreams each night that grow longer as sleep draws to a close. Over a lifetime, a person may dream for five or six full years. How best to examine all that content remains a source of debate.
Dreams typically involve elements from waking life, such as known people or familiar locations, but they also often have a fantastical feel. In dreams, people may live out scenarios that would never be possible in real life, although they aren’t always positive.
People have always tried to figure out the meaning of their dreams, but dream interpretation as a field of psychological study emerged in 1899, when Sigmund Freud published The Interpretation of Dreams. Today, most experts disagree with Freud’s conclusions, and some don’t believe dreams signify anything at all. But people continue to mine them for clues to their inner lives, creative insight, and even hints of the future.
Nightmares can create feelings of terror, anxiety, or despair, and lead to psychological distress or sleep problems like insomnia. Research has identified a range of causes for nightmares, including post-traumatic stress, anxiety—especially the presence of generalized anxiety disorder, dissociation, and physiological changes.
“Re-experiencing” is a common symptom of post-traumatic stress disorder, also known as flashbacks. These involuntary recollections often manifest in the form of nightmares that can cause significant emotional distress. Even when the dreams are not exact replays of a trauma, they may have a strong symbolic or indirect connection to the event.
Terrifying dreams that rouse people from sleep plague children more often than adults, and nightmares can be especially vivid for young children because they may have a harder time separating fantasy from reality. But at least half of grownups also have occasional nightmares, although fewer than 10 percent report frequent or recurring episodes.
Experts recommend that individuals experiencing nightmares tied to stress try to focus on positive elements of their day immediately before bed; catch themselves when they feel themselves ruminating or catastrophizing; and train themselves not to dwell on disturbing images from nightmares. For nightmares tied to PTSD, visualization treatments in which patients replay traumatic memories in “safe” ways have shown potential to bring relief.
Not necessarily. Night terrors, which are primarily experienced by children, cause sleeping people to scream, bolt out of bed, or demonstrate symptoms similar to a panic attack. But night terrors tend to occur earlier in the sleep cycle, while nightmares take place primarily during REM sleep. And unlike nightmares, night terrors are usually not remembered by sufferers, even though they may appear to be awake during the experience.
During lucid dreaming, which most commonly occurs during late-stage REM sleep, a dreamer is aware that they’re asleep, but is able to control events within their dreams, to some extent. Lucid dreamers report willing themselves to fly, fight, or act out sexual fantasies. There are communities dedicated to learning how to lucid dream at will, although evidence that this is possible remains inconclusive.
Research suggests that the brain undergoes a physiological change during lucid dreaming. In fMRI studies, the prefrontal cortex and a cortical network including the frontal, parietal, and temporal zones have been shown to activate when the brain begins lucid dreaming. This appears related to the "waking consciousness” that characterizes lucidity.
Most people do not typically experience lucid dreaming, or do not realize they do, and those who do tend to experience it in a limited way, without full agency. But some experts, and advocates of the potential benefits of lucid dreaming for boosting creativity and confidence, and reducing stress, believe most people can train themselves to experience lucid dreams.
Advocates of lucid-dream training suggest starting with dedicated recording of one’s dreams to gain a greater awareness of the conscious roles they may already play in common scenarios. Another approach is waking up two hours earlier than normal, staying awake for a short time, and then going back to bed, with the goal of increasing awareness of fresh late-stage REM sleep dreams and eventually directing them.