Today, we use the word nightmare much more loosely to describe a vivid, frightening dream that wakes us in the night.  
They are perhaps the most widely researched type of dreaming, probably because they are so hard to ignore.
Often, on waking, our heart is beating faster, we may be sweating and may hear ourselves screaming or crying out as we
approach consciousness. More often than not we are left with a feeling of intense fear, or a certainty that something bad
has just happened, or is about to. There may be an unexplainable terror that something has psychically attacked us whilst
we slept. An apt description of a nightmare, still relevant today, can be found in "An Essay on the Incubus or Nightmare"
by J. Bond (not the 007 one!)

"The nightmare generally seizes people sleeping on their backs, and often begins with frightful dreams, which are soon
succeeded by a difficult respiration, a violent oppression on the breast, and a total privation of voluntary motion. In this
agony, they sigh, groan, utter indistinct sounds, and remain in the jaws of death, till, by the utmost efforts of this nature,
or some external assistance, they escape out of that dreadful, torpid state. As soon as they shake off that vast
oppression, and are able to move the body, they are affected by strong palpitation, great anxiety, langour, and
uneasiness; which symptoms gradually abate, and are succeeded by the pleasing reflection of having escaped such
imminent danger."
So, if you're experiencing nightmares, what can you do about it?
If I had £1 for everyone that has explained away their nightmare by telling me it was because they watched a horror film the
night before, I'd be very rich! Studies do not support the belief that a shocking film, such as a horror film, will "give me
nightmares" as many people like to claim. If you do have a nightmare following such a film, it's likely that your subconscious
is simply using an appropriate, remembered image to tell it's own story.
A nightmare is a slap in the face from the subconscious. It suggests there is a problem, which is either not being faced up
to or that we are having difficulty facing up to. This can be the result of a long-standing problem, or a sudden event that
has shocked or traumatised us. So if you had a nightmare following a night of TV horror, you can be sure that the fear
generated by the film connected to the same energy within your unconscious mind; an energy that is intimately connected
to a very personal issue. Sometimes we are unaware that there is a problem; we may be so busy living inside our
defensive ego that we are totally oblivious to how things are really affecting us. At other times the problem is easy to
identify but we may feel that there's nothing we can do about it, or maybe we don't want to do anything about it. People
who are very good at pushing emotional problems away and pretending they don't exist may be more prone to having
nightmares. It is true that some problems, given time, will go away by themselves. It may take twenty years or more, but
what the heck? Anything's better than facing up to an unpleasant issue. Right?  
Wrong.   You can be sure that the sort of
problems that give rise to nightmares, are affecting your life, your behaviour and your relationships. Why spend twenty
years being directed by unconscious tendencies when, with a bit of courage and a will to explore your life honestly, you
can take steps to put things right and have your life the way it ought to be. If you do this, your life will be enriched and the
nightmares will stop.
Please note, however, that nightmares that are the result of Post Traumatic Stress usually need professional help to be
resolved and are not dealt with here. So please, if you are having recurrent nightmares that are re-playing a past trauma, go
and see your Doctor who will be able to recommend professional therapy.
Nightmare themes are as varied as mankind's fears but probably the most common theme is that of being pursued, stalked
or watched by something that is strange or alien; always hostile and often downright terrifying. You literally feel that your life
or sanity is at stake. Often, we feel we are unable to run away or escape. It's common for instance to feel we cannot move
our legs or that we are stuck in thick, deep mud. These sensations are probably due to the fact that the nightmare is
occurring during REM sleep and the muscle paralysis, that is a completely normal physiological event, is preventing us from
moving our limbs in reality. Whatever your nightmare, the fact that you wake up terrified usually means that you were trying,
unsuccessfully, to escape the danger. It is usually the emotion of fear that instigates these dream experiences. This is the
reason that nightmares are more common in children. When you're small, the world is a very big place and there's a lot to
be frightened of because there's a lot you don't understand. Sneaking out to the tuck shop at playtime may not seem like a
big deal, but what will happen to you if you get found out? It would be interesting to undertake a study of the prevalence of
children's nightmares, to see if they are less common since corporal punishment was abolished in schools.
For adults, the fear is usually easier to recognise and understand. For instance, nightmares often occur during periods of
acute stress; fear of being alone due to a marriage break up, the fear of losing one's job or a fear that a loved one is about
to be taken away, (either through illness, separation or simply children growing up and flying the nest). Even pregnancy has
been known to cause nightmares. This can be understood if one recognises that the parents are approaching a new
situation of which they may have no knowledge, not only in terms of being responsible for a new life but also because of the
changes they must make; their lives will never be the same again and this in itself can be quite scary. In cases such as this,
where life changes are the cause, exploring why we are fearful of the change can allow us to understand ourselves better
and plan coping strategies that will strengthen us and make us more able to deal with our fears. This in itself will help
eliminate the fear of change.
Those people who experience nightmares that seem unrelated to their waking concerns, need to pay special attention.
Often, the things that pursue us in our dreams are those things that we have not acknowledged or will not face up to in our
waking life. That is why they pursue us, to try and gain recognition and acceptance. They can be anything from an unused
or under-utilised talent to an aspect of our character that sabotages everything we try to achieve.
So, please take your nightmares seriously and undertake to investigate them further. Once you bring them into
consciousness and begin to deal with the issue that is causing them, you will find that they will start to change (if they had
been recurrent) or that they will stop all together. It's a matter of record that once we acknowledge our fears and resolve to
do something about them, they cease to be issues in our life. The positive side of all this, is that by addressing and
integrating our fears, we grow as a person and that brings in its wake a whole load of private and professional opportunities
that we may never have thought possible. Fear traps us, it keeps us prisoner, shackled to the dark recesses of our mind. A
life of fear is no life at all. Once you recognise these fears for what they are, and embrace them into your waking life, they
have the power to transform you. Fears that are ignored make you weak, fears that are integrated and acknowledged can
be an enormous source of strength.
Copyright J C Harthan (2005)
"A man (or woman) who has not passed through the inferno of his (her) passions has
never overcome them. They then dwell in the house next door, and at any moment a
flame may dart out and set fire to his (
her) own house. Whenever we give up, leave
behind, and forget too much, there is always the danger that the things we have
neglected will return with added force."

Carl G. Jung. "Memories Dreams Reflections" (Chapter: India)
The Scream

Edvard Munch
Traditionally, nightmare was the name given to a demon or "mare" that
attacked people whilst they slept.  Bayley's English dictionary in 1785, gives
the following definition;

"The nightmare, a disease when a man in his sleep supposes he has a
great weight lying upon him; a devil who has carnal knowledge of a woman
under the shape of a man."

These attacking demons were given the names of incubus and succubus;
ancient terms that are found in the Hebrew
Zohar, where it is stated that
man's erotic dreams are caused by a succubus lying with him to bear evil
It certainly seems that nightmares are more common if you are sleeping on your back. It's also quite common, on regaining
consciousness, to find oneself unable to move. This can be a VERY frightening experience if you don't know what's
happening to you. It's actually due to sleep paralysis, which is completely normal during REM sleep. If, whilst experiencing
this, you muster all your will and strength to turn onto your side, the nightmare and all the associated hallucinations, will
stop instantly.