Johann Henry Fuseli (1741-1825)
Oil on Canvas, 102 x 127 cm
Frankfurt am Main, Goethe Museum
Nightmares are frightening dreams that often awaken the sleeper from Rapid Eye Movement Sleep (REM) sleep. REM sleep is the stage of sleep when we are most likely to have a dream. If you wake up from REM sleep, 8 times out of 10 you will recall a dream. We first hit REM sleep about 90 minutes after we fall asleep. After a REM period our brains go back and cycle through stages 1 to 4 sleep and then enter REM sleep again. This pattern, called a sleep cycle, repeats four to six times per night. Each successive REM period gets longer as the night goes on. That is why nightmares usually occur in the second half of the night (when REM sleep is most prominent). Occasionally, nightmares can occur during stage 2 sleep. Nightmares in stage 2 sleep are often experienced by people who have gone through or are going through traumatic life events.
The key feature of nightmares is that there is a rapid increase in fright or anxiety that builds and almost always awakens the dreamer. However, what is frightening for one person is not necessarily frightening to another. It is up to the dreamer to decide.
If you experience a nightmare, you will likely be frightened completely awake. You won’t be groggy or half asleep. You will quickly become aware of your surroundings and there is rarely any confusion. This is because you are awakening out of REM sleep, a stage of sleep when the brain is quite active. On the other hand, if someone were to have a sleep terror (a sleep terror is different from a nightmare) they would not remember the episode because they occur in the deeper stages of sleep, stages 2 to 4. Although it may look like they have woken up from a nightmare, with the sleep terror, only part of their brain wakes up. The sleep terror will often result in a semiconscious, confused person.
During REM sleep our bodies are paralyzed so that we won’t act out our dreams. That is why we don’t talk, scream or jump out of bed during a nightmare like we would if we were to experience a sleep terror.
Nightmares are most common between the ages of 3 to 6 years. People who have nightmares all the way into adulthood will usually continue to experience nightmares regularly throughout their lifetime. Frequent nightmares only occur in about 1% of adults. About 50% of all adults have occasional nightmares. Understandably, nightmares are worse during periods of stress and are common to victims of post-traumatic stress disorder.
Thanks to L. Orr, BA, RPSGT for her help with this article.