Nightmares are dreams which are terrifying and lead to intense anxiety or fear when you wake up from sleep. This is characteristic of the REM sleep behaviour disorder in which dreams often have a particularly aggressive content. Occasionally however this relaxation is lost and the content of the dream is physically acted out. They then occur at approximately 90 minute intervals during sleep and are most complex and prolonged in the later REM sleep episodes towards the end of the night.ĭuring REM sleep almost all the muscles of the body are totally relaxed so that activities in the dreams cannot be physically expressed. It is unusual for dreams to occur soon after falling asleep since the first cycle of REM sleep is usually around 90 minutes after falling asleep. The content of this type of dream can sometimes be controlled by the subject (lucid dreams).
This occurs particularly in people who are deprived of sleep and with jet lag but may also happen in sleep disorders such as narcolepsy in which the pre and post sleep dreams are particularly vivid.
In REM sleep the sequence of events can be extremely complex and emotionally charged.ĭreams usually occur during sleep but may arise either just before sleep has started or after waking. It is now thought that in NREM sleep any 'dream' content is much simpler with less of a story, less motion and less emotion. There has been much debate about whether dreams occur only in rapid eye movement (REM or dream) sleep or in non-rapid eye movement (NREM) sleep as well. The content of the dream is often something which has happened in the last 2 or 3 days but significant events for the individual which took place many years ago may be recalled and may often be the basis of repetitive dreams. They can be recalled immediately after waking but soon fade from memory.
Dreams and nightmares are characterised by a narrative or sequence of story-like events which are often illogical with people and places disconnected.
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