A child of pre-school age will usually sleep 10 to 12 hours a day. At this age, sleep routines and bed times should be well established. It’s very important to be aware that children of this age can dream violently and have problems with nightmares. Dreams are influenced by the child’s experiences during the day and their imagination, such as large wild animals, so beware of violent bedtime stories and videos or TV.
If your child cries and wakes up with nightmares, they are in need of comfort and reassurance. Go in to them and comfort them by stroking their back and using reassuring words. Try not to wake the child further or ask about what they are dreaming, because usually the child is not really awake and will quickly fall back to sleep. Most often children cannot even remember the next morning that they had a nightmare. On the other hand, if the child wakes up screaming, bathed in sweat and is inconsolable, it may be a good idea to speak with the child about the dream as it can help him to talk about what has frightened him.
Nightmares should not be confused with night terrors. Nightmares occur during the dream phase of sleep known as REM sleep. Most people enter the REM stage of sleep sometime after 90 minutes of sleep. The circumstances of the nightmare will frighten the sleeper, who will often wake up with a vivid memory of a long movie-like dream. Night terrors, on the other hand, occur during a phase of deep non-REM sleep, usually within an hour after the subject goes to bed. During a night terror, which may last anywhere from five to twenty minutes, the child is still asleep, although his eyes may be open. When the child does wake up, he may have no recollection of the episode other than a sense of fear. Children suffering a night terror can put themselves in serious danger without realising it. If your child is experiencing night terrors, there is little you can do other than sit with them until it’s over to keep them safe.
Source: netdoktor.dk, nightterrors.org/