What are nightmares and why do they appear
We have all had nightmares. Sometimes we remember them as soon as we wake up or a few hours later. They may even startle us and cause us to wake up suddenly.
But in other occasions it is possible that we do not remember anything; We only feel that we have had a strange or horrible dream because we get up with an uncomfortable feeling, but nothing more. 
For example, we are in the middle of a good, wonderful sleep. We walk along a dirt road, full of trees around. We listen to the sound of the birds and we feel calm, relaxed. But suddenly we see a wolf, which starts to chase us and we tend to keep running, fleeing. We move in bed, trying to run away and run. We scream, and finally we wake up startled.
What is a nightmare?
This is probably an exemplified description of what we might define as a nightmare. In the words of the Royal Spanish Academy, a nightmare is an anguished and tenacious reverie.
While the Dictionary of Medical Terms of the Royal National Academy of Medicine defines it as aparasomnia that occurs during the REM phase, so that, under physiological conditions, there are no vocalizations or body movements due to the muscular hypotonia of that phase of sleep.
That is to say, a nightmare consists of a terrifying reverie that causes us fear or anxiety.
When do nightmares happen?
When we sleep, usually during the night, we enter two different states of sleep. The first of these is known as "slow wave sleep" (NO-REM), a phase of sleep in which there is greater relaxation and a deeper rest occurs, which tends to last about 90 minutes. 
After those 90 minutes we enter the dream in which there are rapid movements of the eyes, known as REM. It is during the REM sleep phase that most nightmares occur, estimating that between 4 to 6% occur during the SWS phase.
However, when the nightmare occurs during sleep, NO-REM is known by the name of night terror, and in this occasion it is very usual that people do not remember the content of these nightmares, only tending to wake up screaming or sweating.
Why do they happen?
In the opinion of many experts, most people have nightmares for one of the following reasons:
- Weak emotional state, with anxiety, nervousness or insecurity.
- The memory of an event that has caused a trauma, either consciously or subconsciously.
- Some external factor that the person is not aware of but his brain does detect.
We must bear in mind that nightmares tend to be much more common among the little ones, so that they tend to be less frequent when we are older, in the adult stage. However, that does not mean we do not have them: we can also experience occasional nightmares. 
Among the causes that most commonly cause the appearance of nightmares are the anxiety As the stress, in addition to situations or experiences that have caused us a trauma; for example, the death of a loved one, having survived an accident or a catastrophe ...
There are also other causes, such as excessive alcohol consumption or the alcohol withdrawal syndrome itself, sleep apnea (breathing disorder during sleep), diseases that cause high fever, certain sleep disorders or side effects of a drug or medication.
On the other hand, did you know that eat right before going to bed Is it also another cause related to nightmares? The reason is found in that it increases both the metabolism of our body and brain activity, at a time that is not really adequate. This article is published for informational purposes only. It can not and should not replace the consultation with a Psychologist. We advise you to consult your trusted Psychologist.
