You wake up sweating and terrified. You've been tortured, chased by a zombie, left by your partner – but it's all in your dreams. You scramble for the light switch, force yourself back into reality.
Research shows that the most frequent recurrent dreams in adults are pseudo-nightmarish, meaning you'll dream of being endangered (being chased and/or threatened with injury, for instance), being alone and trapped (such as in an elevator), facing natural forces (such as volcanic eruptions or tsunamis) or even even something like losing your teeth.
According to Dr Irshaad Ebrahim, MD MRCPsych, Specialist Neuropsychiatrist in Sleep Disorders at the Constantia Sleep Centre, almost all of us are vulnerable at some stage to having nightmares. There are different types and severity.
"If we consider only attack dreams, which are one of the most common nightmare themes, the lifetime prevalence varies from 67% to 90%. Pursuit, a closely related, highly disturbing theme, has a lifetime prevalence of 92% among women and 85% among men," he says.
Read: To dream the impossible dream
Types of dreams
Nightmares are classified into different categories:
Repetitive dreams: Such as post-traumatic nightmares, these depict, with numerous, highly similar versions, an unresolved experience, such as a motor vehicle accident or war trauma.
Recurrent dreams: These depict conflicts or stressors metaphorically over time. They're also primarily unpleasant in nature.
According to Ebrahim, people with recurrent dreams show less successful adaptation on measures of anxiety, depression, personal adjustment, and life-events stress, than those without recurrent dreams.
Interestingly, if these dreams stop, and don't return, this can reflect an upturn in well-being.
Read: The importance of dreams
Childhood and nightmares
Be it the bogey man or a monster in the cupboard, children are prone to nightmares and have them far more frequently than adults.
"Prevalence increases through the first decade of life and diminishes from adolescence to early adulthood. For example, when nightmare problems were defined as lasting for longer than three months, their prevalence was 24% for ages two to five; 41% for ages six to 10, and 22% for age 11."
While you're never too old to have a nightmare, age is a factor in how often you get them.
"Children, young adults and older adults have nightmares at least sometimes, with a prevalence of 30% to 90%; 40% to 60%; and 60% to 68%, respectively."
Gender is a factor
Ebrahim notes that in one study of both young and teenage boys and girls, results showed that girls suffered more nightmares.
"Of bad dreams at age 13, the boys came out at 25%, versus the girls at 40%. And at age 16 the boys were at 20% while the girls were still at 40%."
He adds that this trend continued into adulthood, where the frequencies of nightmares of one or more a month were measured and it was found that only 8% of men, compared to 30% of women, had nightmares.
Nightmares vs. bad dreams
Is there a point at which a bad dream crosses the invisible threshold into nightmare status?
Some believe that only a nightmare, and not a bad dream, awakens the sleeper. "Some researchers argue that the 'awakening' criterion should indeed designate nightmares, but that disturbing dreams which do not awaken - otherwise known as 'bad dreams' - should nevertheless be considered clinically significant," Ebrahim says.
"Whether or not the person awakens presumably reflects a dream's emotional severity, but it's not the only index of severity," he says.
Ebrahim adds that there are other factors which also need to be taken into consideration.
"Firstly, in patients with various psychosomatic illnesses, even the most macabre and threatening dreams do not necessarily produce awakenings.
"Secondly, less than one fourth of patients with chronic nightmares report 'always' awakening from their nightmares, and these awakenings don't correlate with either nightmare intensity or psychological distress."
"Thirdly, among subjects with both nightmares and bad dreams, approximately 45% of bad dreams are rated as having an emotional intensity that equals or exceeds that of the average nightmare."
According to Ebrahim, researchers have thus come to define nightmares more inclusively with respect to their emotional tone.
"Some researchers have argued that nightmares can involve any unpleasant emotion, an opinion that is consistent with patients' reports that their nightmares involve intensification of many unpleasant emotions, such as sadness or anger. Nonetheless, fear remains the most frequently reported nightmare emotion."
What can be done?
The good news is that if you do suffer from terrible nightmares, there are some things you can do to stop them and ensure a better night's sleep:
Stress: If you're stressed it often helps to talk to friends and family about the problem.
Exercise: A regular fitness routine focusing on cardio exercise will help you sleep better and, hopefully, without dreaming.
Relax: Relaxation techniques can help you sleep and reduce stress and anxiety - two of the major causes of nightmares.
Routine: Try to go to bed at the same time every night and get into a pattern of waking up at the same time.
Avoid sleeping pills: Steer clear of tranquilizers and sleeping aids, as well as caffeine and other stimulants, especially before bedtime.
Check medication: Often the nightmares might be a rather unpleasant side effect of medication you're on. Contact your doctor to find an alternative.
Substance abuse: Nightmares are most common – and avoidable - among people who abuse alcohol and/or drugs. Users should find a way to quit as soon as possible.
When to seek help
Should you not fit into any of the above categories, and you have nightmares several times a week or they prevent you from getting a good night's sleep, it's time to seek professional help.
Sources: Dr Irshaad Ebrahim MD MRCPsych, Specialist Neuropsychiatrist in Sleep Disorders, Constantia Sleep Centre; US National Library of Medicine