Why Do We Have Nightmares?

A source of confusion or anxiety for most, nightmares may serve a very beneficial purpose, according to researchers.
Nightmares are helpful to our survival or else they probably would have been done away with by evolution, said Deirdre Barrett, a psychologist at Harvard University. Barrett theorizes that nightmares act as the brain's way of focusing a person's attention on issues they need to address.

"Nightmares probably evolved to help make us anxious about potential dangers," Barrett said. "Even post-traumatic nightmares, which just re-traumatize us, may have been useful in ancestral times when a wild animal that had attacked you, or a rival tribe that had invaded might well be likely to come back."
But this evolutionary alarm bell may not be so useful in today's world.
"With the modern dangers of house fires, car crashes, rapes and muggings unlikely to repeat soon for the same victims, this adaptive mechanism doesn't always serve us well," Barrett exlpained. "However, some nightmares may be calling to your attention something you might do well to worry aboutor something that, once you are more conscious of the concern, you can convince your unconscious to stop wasting time on."
How to stop a nightmare
How does one go about convincing their subconscious to stop repetitious nightmares?
"People can come up with a different ending to the nightmare - a mastery dream," Barrett told Life's Little Mysteries. "Some people prefer to fight off an attacker, some people would rather be rescued by someone else. Some want a realistic solution, for others, a metaphoric resolution is more satisfying."
"Once they've come up with their preferred ending, they can rehearse this while awake and then at bedtime, to remind themselves that they want to have this ending, should the nightmare occur again."
However, before trying to change a nightmare, Barret recommends attempting to decipher its true meaning. Sometimes, analyzing a bad dream can help a person see its correlation to their daytime worries.
Dreamscapes across cultures
Some cultures and religions, such as the Native American Lakota tribe, rely on dreams and nightmares to point them in the right direction when an important decision needs to be made, according to "The Dream Seekers: Native American Visionary Traditions of the Great Plains," (Univ of Oklahoma Press, 1994).
In 2005, Dutch-sponsored researcher Elizabeth Mohkamsing-den Boer recorded the nightmares of indigenous Surinamese and Australian tribes. She found that their dreams often correlated to significant events that the dreamers were either experiencing or anticipating in their lives.
During her research, the tribes people frequently told Mohkamsing-den Boer that "dreams prepare your emotions," as they believe that nightmares and dreams provide guidance when a difficult decision needs to be made. Mohkamsing-den Boer concluded that nightmares have a helpful role during times of change or uncertainty, and refers to them as transitional dreams.
Nightmares are a normal part of sleep , and their frequency varies from one person to the next. While it may seem that having numerous nightmares in a short period of time is a bad sign, it may be that people who often experience nightmares simply have more vivid dreams in general, according to Barrett.
"People should seek help for their nightmares if they are carrying over into their daytime mood and making them very anxious, or if they are making them afraid to go to sleep," Barrett told Life's Little Msyteries. "However, some people have frequent nightmares and don't particularly mind them they even find them interesting."