Psychoactive Substances

Abstract

IntroductionThis chapter discusses some substances that are particularly likely to induce hallucinations. Many such drugs are available in nature and have long histories of use; more have emerged from laboratories either accidentally or as the result of purposeful research. Many more substances than these can elicit hallucinations, given the natural corporeal variations among individuals. For example, antidepressants such as paroxetine (Shimizu et al. 2010 ) or citalopram (Capaldi and Carr 2010 ) occasionally induce auditory hallucinations, which tend to resolve quickly after the drug is discontinued. Even the lack of an ordinary biological componentsuch as water in dehydration -can cause similar effects.This chapter focuses on a few substances often taken for the purpose of hallucination. Some effects that are typically sought by hallucinogen users are alterations of sensory perception, interpretation, and context. Changes in visual perception are perhaps the canonical hallucinogen-induced effect. For example, a normal aspect of human sight called "persistence of vision" enables us to perceive subsequent still images as a seamless motion picture, or a moving dot of light as a complete picture in a laser show. Some hallucinogens extend this ability so that a larger set of images is retained in perception -the line behind the laser dot becoming longer -an effect commonly known as "trailers." Spots or afterimages seen upon closing one's eyes