Nightmare is the term currently used to refer to a dream which causes a strong unpleasant emotional response from the sleeper, typically fear or horror, or the sensations of pain, falling, drowning or death. Such dreams can be related to physical causes such as a high fever, or psychological ones such as psychological trauma or stress in the sleeper's life, or can have no apparent cause. If a person has experienced a psychologicaly traumatic situation in life, for example, a person who may have