A nightmare is an unpleasant dream that can cause a strong negative emotional response from the mind, typically fear or horror, but also despair, anxiety and great sadness. The dream may contain situations of danger, discomfort, psychological or physical terror. Sufferers usually awaken in a state of distress and may be unable to return to sleep for a prolonged period of time.
Nightmares can have physical causes such as sleeping in an uncomfortable or awkward position, having a fever, or psychological causes such as stress, anxiety, and ingestion of opioid drugs used in pain killers such as oxycodone and hydrocodone. Eating before going to sleep, which triggers an increase in the body's metabolism and brain activity, is a potential stimulus for nightmares. Recurrent nightmares that can interfere with sleeping patterns and cause insomnia may require medical help.