Peralta & Cuesta (Reference Peralta and Cuesta1999) accurately criticise the significant bias of prior studies, namely the inclusion of patients in whom schizophrenia was diagnosed using criteria that strongly rely upon first-rank symptoms. In their study the authors clearly showed the high prevalence of first-rank symptoms in schizophrenia and non-schizophrenic psychosis (diagnosed mainly by Feighner's criteria). They conclude that first-rank symptoms are not useful in differentiating schizophrenia from other psychotic disorders. This obviously seems correct, since Schneider (Reference Schneider1959) himself never intended to differentiate schizophrenia from other psychoses (mainly schizophreniform disorder, schizoaffective disorder and atypical psychosis), as these disorders were part of the Schizophrener Formenkreis in Schneider's system. Therefore, we strongly disagree with Peralta & Cuesta that the diagnostic relevance of first-rank symptoms should be to differentiate schizophrenia from other psychotic disorders.
Moreover, the authors conclude that until more evidence is available, first-rank symptoms “should not receive particular emphasis in the ICD-11 and DSM-V diagnostic criteria for schizophrenia”. Peralta & Cuesta omit a second possible conclusion : that the development of a nonschizophrenic psychosis (which, in fact, includes many of the diagnostic criteria of schizophrenia in any psychiatric classification) seems an artificial division of one clinical entity and this group should be considered as a schizophrenia subgroup in the ICD-11 and DSM-V.
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