What are hallucinations?

Quick Answer
The perception of sensations without relevant external stimuli.
Expert Answers
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Society often associates hallucinations with psychotic behavior, because schizophrenia and other forms of mental illness frequently involve hallucinations. Another widely publicized example of these symptoms is the use of hallucinogenic drugs, for example, lysergic acid diethylamide (LSD) or marijuana. One must also consider the role of hallucinations in religious experiences and megalomania; such perceptions occur when ordinary people are subjected to extraordinary stimuli.

Medical science has resisted the study of hallucinations and treated them as symptoms of mental illness. Increasing evidence shows, however, that they arise from specific brain and nervous system structures involving specific biological experiences and common reactions to stimuli. Consequently, people suffering from drug abuse, alcoholism, and disorders similar to Alzheimer’s disease, in which severe loss of memory can provoke illusions, are subject to hallucinations.

Since a hallucination can be the result of physical causes as well as the traditional mental unbalance of schizophrenia or bipolar disorder, it is difficult to categorize its symptoms. An individual experiencing hallucinations at times other than waking or falling asleep should see his or her doctor. If the incidents are attributable to a serious illness, early detection is possible. If they are an effect of a particular medication, the prescription should be changed immediately.


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