What Is a Dream? Why do we forget what we dreamed after waking up?

If you wake in the morning feeling disappointed that you again don’t recall any dreams that you had overnight, you might question: Why can’t I remember my dreams? Learn about the nature of dreams, the association of vivid dreams with rapid eye movement (REM) sleep, normal sleep patterns and the pattern of dreaming, triggers of dream recall like untreated sleep apnea, and how you might learn to better remember your dreams.

What Is a Dream?

Nearly everyone has had a dream at some point in life; even blind people are known to dream. The frequency of dream recall may vary or even fade at points in one’s life. A dream is a series of thoughts, images, or sensations that occur in the mind during sleep. It is a function of the brain. Dreaming may occur as specific regions of the brain are activated through sequenced electrical patterns and chemical activity.

Vivid dreams—like a movie that occurs with you as the actor—are associated with rapid eye movement (REM) sleep. This state of sleep was first discovered by William Dement, MD, PhD, considered the father of sleep medicine. REM is associated with intense activity within the brain. In fact, the brain uses as much energy (and glucose) in REM as it does during wakefulness. The muscles controlling the eyes are active, as is the diaphragm that is responsible for preserving breathing.

The rest of the body’s major skeletal muscles are paralyzed during this state. This prevents the acting out of dreams from occurring (and abnormalities of its regulation account for both sleep paralysis and REM sleep behavior disorder).

The exact purpose of dreaming is still being examined. It seems to have an important role in memory consolidation, including the elimination of irrelevant daytime experiences.

It also is important to learning and problem solving.

Curiously, it is possible to experience fragmentary dreams in non-REM sleep. This includes the lighter stages of sleep (called stage 1 and stage 2) and slow-wave sleep (called stage 3). It is believed that the dream content of non-REM is more simplistic. It may be the dream of an image, an idea, or concept that is more static. If REM-related dreams are a movie, non-REM dreams may be likened to a photograph.

The nature of dreams, and their specific meaning, has been a subject of interest for millennia. The famous neurologist and founder of psychoanalysis, Sigmund Freud, MD, famously explored the topic in his seminal work from 1900 called The Interpretation of Dreams. There is no consensus on the scientific basis for the interpretation of dream content; reflection and derivation of meaning may be best reserved as a personal exercise.

The Normal Patterns of Dreaming in Sleep

It is normal to dream, but it is common to not recall the dreams that occur. The dreaming state can be identified by measurements made as part of a diagnostic polysomnogram, including recording of the electroencephalogram (EEG), the electrooculogram (EOG), and the electromyogram (EMG).

The tell-tale signs of REM sleep include an active brain, rapid eye movements, and a transient loss of muscle tone.

REM sleep occurs at intervals throughout the night. The first period of REM may be noted 90 to 120 minutes into the night. If it occurs early, in less than 15 minutes, this may be a sign of narcolepsy. REM periods become more prolonged towards morning. As a result, the last third of the night may include mostly REM sleep. It is common to wake in the morning out of the last period of REM.

Just because they are not recalled, the dreams associated with REM sleep are likely still occurring.

There may be variability night to night and across the lifespan. What accounts for the lack of dream recall?

Why Dreams May Be Forgotten

There are a few possible explanations for dreams that cannot be remembered. First, it is possible that REM sleep is not occurring (or at least not occurring as much as normal). Medications may suppress REM sleep. In particular, antidepressants seem to have a powerful influence by delaying the onset or reducing the amount of REM sleep. Alcohol may also act as a REM sleep suppressant, at least until it wears off.

If REM sleep is occurring, the vivid dreams that are associated with it may not be recalled. If there is a transition from REM sleep to another state of sleep (most often stage 1 or stage 2), prior to recovering consciousness, the dreams may be forgotten.

As a general rule, dreams fade quickly after waking. The electrical signals and chemical signatures that constitute the experience of the dream may disappear as wakefulness ensues, like a message written on a fogged mirror that vanishes as the steam evaporates. It is possible for elements of the dream to be recalled later in the day, perhaps triggered by an experience that reactivates the same area of the brain that created the dream overnight.

Particularly memorable dreams may create an impression that persists for decades. Recounting the dream to another person may help to stabilize the memory. Dreams (or nightmares) that are associated with intense emotions, including fear, may also stick in the mind. The amygdala is an area of the brain that may help to elicit these emotion-laden dreams.

It is more likely that dreams will be remembered if the state of REM sleep is fragmented. Alarm clocks notoriously interrupt REM sleep towards morning.  It is possible to fall back asleep and to re-enter the same dream experience repeatedly.

Sleep disorders may impact dream recall. Untreated obstructive sleep apnea may also contribute to fragmented REM sleep as disturbed breathing occurs due to relaxation of the airway muscles. For some, this may lead to increased dream recall (including dreams of drowning or suffocation). Sleep apnea may likewise lead to REM sleep deprivation and effective CPAP therapy may cause a profound rebound of REM sleep. People with narcolepsy also experience sudden sleep transitions that contribute to dream recall, sleep-related hallucinations, and sleep paralysis. Poor sleep habits, stress, and psychiatric conditions may also fragment sleep and increase dreaming and recall.

Ways to Better Remember Dreams

If you are interested in improving your dream recall, consider a simple change: keep a dream journal. By keeping a pen and a piece of paper (or perhaps a legal pad or blank notebook) on the nightstand next to the bed, it becomes easy to quickly record dreams immediately upon awakening, before they have had a chance to fade. This may encourage improvements in dream recall. If the scribbled notes can be interpreted later in the morning, it may be possible to reflect on the meaning of the dreams.

Dreams are a fascinating part of sleep and life is enhanced by an enriched experience of these phenomena. Though you may feel distressed by not remembering dreams, rest assured that this state of sleep is likely still occurring. The benefits yielded, from memory processing to learning and problem solving, are likely just below the surface of awareness. As you fall asleep, imagine a world that might be, and it may come to you in the night.