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 .