Pathogenesis and symptomatology of hallucinations (delusions) of organic brain disorder and schizophrenia.

In this review article, in order to explore the mechanisms underlying the hallucinations/delusions of schizophrenia, we discuss the contribution of the following four questions: (i) can an understanding of dreams contribute to our understanding of the genesis of halluciations and/or delusions; (ii) are the mechanisms underlying psychotropic drug-induced psychoses the same as those underlying the hallucinations and/or delusions in schizophrenia; (iii) does disturbed consciousness contribute to the manifestation of psychotic features; and (iv) are the psychoses caused by organic brain disorders any different to the hallucinations and/or delusions seen in schizophrenia? We conclude that there is a strong association between drug-induced hallucinations or hallucinations associated with organic brain disorders and simple hallucinosis or fluctuations in arousal level. Because intermediate configurations and/or cross-staining phenomena exist for hallucinations and delusions, especially in schizophrenic disorders, it is difficult to isolate the hallucinations and to recognize them as being abnormal experiences.