Hallucination

Hallucination is a false perception in any of the five sensory modalities when no external stimulus exists, as when a nonexistent object is seen. Hallucinations may occur in the twilight state between sleeping and awakening, or in delirium, delirium tremens, or exhaustion; they also may be induced under hypnosis. The visual sense is most often affected. Persistent hallucinations are characteristic of schizophrenia. In one type of schizophrenia, victims believe that they hear accusing or commanding voices, to which they may react in panic, with abject obedience, or with attempts at self-protection or even suicide. Hallucination is distinguished from illusion, a false perception of an actual stimulus, and is common following self-administration of certain drugs such as mescaline, marijuana, and lysergic acid diethylamide (LSD). Both illusions and hallucinations can be drug induced. See Drug Dependence; Psychoactive Drugs.