Oneirophrenia is a hallucinatory, dream-like state caused by several conditions such as prolonged sleep deprivation, sensory deprivation, or drugs. Oneirophrenia is often confused with an acute case of schizophrenia due to the onset of hallucinations. The severity of this condition can range from derealization to complete hallucinations and delusions. Oneirophrenia was described for the first time in the 1950s but was studied more in the 1960s. Although it is still cited in diagnostic manuals of psychiatry, such as DSM-IV and in the International Statistical Classification of Diseases and Related Health Problems (ICD), oneirophrenia as a separate entity is out of fashion nowadays.
