A nightmare is a dream occuring during rapid eye movement (REM) sleep that brings out feelings of strong fear, terror, distress, or extreme anxiety. Nightmares are usually in the latter part of the night and wake up the sleeper, who is able to remember the content of the dream.

See also:

• Night terror
• Sleep disorders

Nightmares tend to be more common among children and become less frequent toward adulthood. About 50% of adults have occasional nightmares, women more often than men.

Anxiety and stress are the most common causes of nightmares. A major life event occurs before the nightmare in most cases.

Other causes of nightmares include:

• Abrupt alcohol withdrawal
• Breathing disorder in sleep (sleep apnea)
• Death of a loved one (bereavement)
• Excessive alcohol consumption
• Illness with a fever
• Reaction to or side effect of a drug
• Recent withdrawal from a drug, such as sleeping pills
• Sleep disorder (narcolepsy, sleep terror disorder)

Eating just before going to bed, which raises the body's metabolism and brain activity, may cause nightmares to occur more often.