Dreams and Nightmares: What They Are, Why They Occur

by Eli Hendel, M.D. Medical Reviewer

Dreams are a normal part of sleep physiology. While there is not yet a clinical consensus on what physical or mental purpose dreams serve, it appears likely that they incorporate recent experiences — as well as the emotions associated with those experiences — and link them with past memories in order to create new memories that can be referenced later. Nightmares, meanwhile, are essentially bad dreams associated with negative feelings such as fear and anxiety.

Dreams are known to occur when the sleeper is close to waking — which is one reason we can so vividly recall some of our dreams. On the other hand, it’s common for sleepers not to recall all of their dreams.

Dreams occur during a period of sleep called rapid eye movement (REM), during which time many active parts of the brain are especially active. When strong emotional experiences are associated with dreams, our brain protects us from harm by sending signals through the spinal cord to decrease the body’s muscle tone so that we don’t physically act (while asleep) on those dreams. Rapid eye movement sleep occurs in cycles, usually following the three stages of non-REM sleep. The cycles begin no sooner than 90 minutes after sleep starts, beginning as short cycles that become longer as the night goes on, with the longest REM periods occurring just before awakening.

Dreams can become a problem when they disrupt sleep and also when the fear of nightmares prevents sleep. Thus it makes sense that kids are most vulnerable to the impact of nightmares, because they don’t yet have the emotional tools to deal with their anxiety.

Nightmares are different than night terrors, which are commonly experienced by children. Night terrors specifically occur during non-REM sleep stages and are entirely driven by emotion with no cognitive content.

(The word nightmare itself derives in part from the Old English word for "monster" (mære), and for ages, people believed that horrific dreams came about due to the exertions of a goblin-like creature that rode on sleepers' chests, suffocating them.)

Until the 1700’s this thought even prevailed in the medical literature, which described a nightmare as a disease where during sleep a great weight lays on man. After that point, dreams were not known as supernatural events but products of gastric upset caused by rich food. During the twentieth century, Freud and Jung, famous psychiatrists, developed the psychoanalytical theory and considered dreams as “wish fulfillments” of repressed desires. Nightmares were strong expressions of mental conflict over these desires. The psychoanalysis of the dreams was a tool used to explore those conflicting desires.

It was not until the 1950s that REM sleep was discovered. By that point, nightmares were widely seen as symptoms or components of disorders, e.g., post traumatic stress disorder. The treatment of nightmares was geared toward finding the underlying cause, and once that was identified, presumably the bad dreams or nightmares would vanish.

Clinicians still often try to interpret what a patient’s dreams mean or represent. There are some common elements, or scripts, to certain dreams. Some common dream patterns include:

  • Dreams in which the sleeper is contacted by someone who is dead or recently passed away often occur in those suffering anxiety about a personal illness.

  • Nightmares about missing a special event are indicative of someone who is in a fast-paced, high-pressure job or situation.

  • A dream about being naked in public may be related to individuals who have problems with their self-image or someone who suffers with low self-esteem.

  • Dreams about being trapped are common in those who have claustrophobia and also can be experienced by individuals who aren’t able to get out of an unpleasant, ongoing situation (financial, work, or relationship related).

  • A very common dream theme involves a person being chased and can often represent fear of confronting someone in order to resolve a conflict in their lives. It is often a sign of not being able to face a confrontation comfortably.

Recurrent nightmares often accompany post traumatic stress disorder (PTSD) but in this case, the nature of the bad dreams or nightmares is different than in ordinary nightmares. In PTSD, a traumatic experience is recreated in the dream and experienced over and over again, and unlike traditional bad dreams, there is a more striking similarity to the initial experience. The challenge here is not to determine the significance of the dream (which is clear), but to try to stop the phenomenon of reliving this bad experience.

To deal with nightmares associated with PTSD, there is a technique called imagery rehearsal therapy. Initially described by Harvard psychologist Deidre Barrett, Ph.D., the therapy involves rehearsing the situation mentally during wakeful hours and gradually changing the ending.

Overall, dreams serve a useful purpose for emotional learning and mental stability. It is the goal of mental health providers to ensure that dreams fulfill their intended purpose, without worsening underlying disorders and without instigating health problems like insomnia. If you suffer with recurrent nightmares that interfere with quality sleep or that instigate a cycle of insomnia, seek medical help.

Eli Hendel, M.D.
Meet Our Writer
Eli Hendel, M.D.

Eli Hendel, M.D., is a board-certified internist/pulmonary specialist with board certification in Sleep Medicine. An Assistant Clinical Professor of Medicine at Keck-University of Southern California School of Medicine, and Qualified Medical Examiner for the State of California Department of Industrial Relations, his areas include asthma, COPD, sleep disorders, obstructive sleep apnea, and occupational lung diseases. Favorite hobby? Playing jazz music.