Schizophrenia: the nature of the psychological disturbance and its possible neurochemcial basis.

The diagnosis of schizophrenia is established principally by the presence of certain psychological symptoms which although subjective can be reliably assessed by standardized interviewing procedures. The most characteristic symptoms (Schneider's first-rank symptoms) fall into three groups: (a) auditory hallucinations of particular types, (b) 'ego-boundary disturbances', including intrusions into the stream of consciousness attributed to external agencies, and (c) delusional perception. Symptoms closely resembling those seen in schizophrenia can be induced in non-schizophrenic individuals by amphetamine-like drugs, and both these symptoms and those of schizophrenia are ameliorated by neuroleptic drugs (the major tranquillizers). Amphetamines facilitate and neuroleptic drugs diminish neural transmission mediated by the chemical substance dopamine. In recent post-mortem studies on patients who had suffered brom schizophrenia, it was found that dopamine release was not increased. However, in some cases there was evidence of increased sensitivity of the dopamine receptor.