What are some of the major causes of hallucinations?
Hallucinations can be caused by a multitude of etiologies, but the essential common theme is aberrant activation of the primary sensory cortex.
Examples include focal epilepsy, toxic (including hallucinogenic substances) and metabolic encephalopathy (including delirium, interictal and postictal hallucinations), rapid eye movement (REM) sleep intrusion (including parahypnagogic and parahynopompic hallucinations—considered normal), and release phenomena (e.g., Charles Bonnet syndrome, sensory deprivation).
The presence of hallucinations should prompt workup to rule out these known causes.
Hallucinations may be part of the phenomenology of schizophrenia, but schizophrenia is a syndrome and should not be thought of as a cause of hallucinations.
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