In common current usage, the term nightmare refers to dreams of particular intensity, with content that the sleeper finds disturbing, related either to physiological causes, such as a high fever, or to psychological ones, such as unusual trauma or stress in the sleeper's life. The occasional body movements seen in nightmares may have a use in awakening the sleeper, thus helping to avoid the frightening dream-situation.

Occasional nightmares are commonplace, but recurrent nightmares can interfere with sleep and may cause people to seek medical help. A recently proposed treatment consists of imagery rehearsal (PMID 15984916). This approach appears to reduce the effects of nightmares and other symptoms in acute stress disorder and post-traumatic stress disorder^*.

Lucid dreaming practitioners claim that it can help conquer nightmares of this type ^*, rather than of the traditional type (see below).

Night Terrors