The words that follow are written in part from the perspective of a former mental health professional trained in Abnormal Psychology. Though I left the field to become a full-time writer, I have continued my studies in the mental health realm. Attributions from outside sources are included, and linked.
The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), is published by the American Psychiatric Association (APA) and utilized as the standard classification of mental diagnoses by mental health professionals in the United States. See this article from Psychiatry.org for further information.
Nightmare Disorder is an accepted and defined mental health disorder, generalized in the DSM-5 as the following: repeated awakenings with recollection of terrifying dreams, usually involving threats to survival, safety or physical integrity. For an expanded DSM-5 definition, see Medscape.com article: What are the DSM-5 Diagnostic Criteria for Nightmare Disorder?
From the article: Occasional nightmares usually are nothing to worry about. Nightmares may begin in children between 3 and 6 years old and tend to decrease after the age of 10. During the teen and young adult years, girls appear to have nightmares more often than boys do. Some people have them as adults or throughout their lives.
This piece refers to sufferers within the latter group, specifically, those adults for whom nightmares are considered chronic or acute.
Psychology of Dreams and Nightmares
There is no specific consensus on the cause or psychology of either dreams or nightmares. There exists, however, a commonly-held theory that certain mental health conditions can increase the vividness and occurrence of both. From WebMD.com: There can be a number of psychological triggers that cause nightmares in adults. For example, anxiety and depression can cause adult nightmares. Post-traumatic stress disorder (PTSD) also commonly causes people to experience chronic, recurrent nightmares. Nightmares in adults can be caused by certain sleep disorders. See here for a WebMD.com article, “Nightmares in Adults,” which lists possible causes and treatments.
The WebMD piece is consistent with the DSM-5 entry on Nightmare Disorder, as well as the American Psychiatric Association‘s view of causality. See here for their article, “What are Sleep Disorders?”
Regarding the concept of sleep disorders in general and nightmares specifically, it is agreed — as written in the linked articles herein — that it is time to seek help from a medical professional if sleep disorders, including nightmares, interfere with day-to-day functioning, which includes an ability to focus and a tendency to be consistently tired during the day.
For a further look at sleep disorders in general, my NewsBreak article, “If a Loved One is Taking Prescription Painkillers or Aspirin for a Sleeping Disorder, Look for Signs of a Larger Problem,” can be found here.
Nightmares can be scary, and also resultant from generalized sleep disorders. Again, though, I must stress that when professionals speak about cause in this regard, these are hypotheses only. Quoting from the Mayo Clinic’s website: Nightmare Disorder is referred to by doctors as a parasomnia — a type of sleep disorder that involves undesirable experiences that occur while you're falling asleep, during sleep or when you're waking up. Nightmares usually occur during the stage of sleep known as rapid eye movement (REM) sleep. The exact cause of nightmares is not known. See here for the Mayo Clinic article on the matter, “Nightmare Disorder Symptoms and Causes.”
Nightmares are scary and can be dangerous. At times, according to professionals, a sufferer may become too scared to fall asleep. At other times, they may self-medicate.
Be sure to seek medical help if you believe you have a nightmare-related sleep disorder.
I hope this has helped. Thank you for reading.