Exorcism, the practice of attempting to drive out demons that supposedly inhabit humans, has flourished in times and places where there is ignorance about mental states. In the Middle Ages when brain disorders like epilepsy were not understood, and the concept of mental illness was unrecognized, the Church taught that demons could take control of an individual, citing biblical examples. Behavior that would today be attributed to aberrant mental conditions such as schizophrenia provoked the rite of exorcism.

Despite the advent of modern psychiatry and a more enlightened modern view, belief in demon possession continues, although the Catholic church has updated its 1614 guidelines for expelling demons, urging exorcists to avoid mistaking psychiatic conditions for possession. The notion that demons exits and can control people was given a boost in modern times by the 1973 movie The Exorcist, inspired by a "true story" that, however, does not stand up to scrutiny. (See Joe Nickell, "Exorcism! Driving Out the Nonsense," Skeptical Inquirer, January/February 2001, pp. 20-24.)

The Exorcist tapped into moviegoers' subconscious fears and many vomited or fainted at the special effects spectacle--behavior that satirized by Mad magazine in its October 1974 issue, shown above.