The validity of studies on the diagnostic significance of first-rank symptoms (FRS) for schizophrenia has been put in doubt because of a poor compliance with Schneider's criterion for their definition and the lack of use of the phenomenological method for their assessment. In this study, using a rigorously phenomenological approach to elicit FRS, we examined (a) the degree to which unequivocally present FRS differentiated schizophrenia (n=513) from other psychotic disorders (n=633), and (b) the comparative validity between FRS and other reality-distortion symptoms against 16 external validators in the whole sample of psychotic disorders (n=1146). Diagnostic performance indices (with 95% CIs) of FRS for diagnosing schizophrenia were as follows: sensitivity=0.58 (0.54−0.61), specificity=0.65 (0.62−0.67), positive predictive value=0.57 (0.54−0.60) and negative predictive value=0.65 (0.63−0.68). While the overall association pattern of FRS and non-FRS scores with the validators was rather similar, three validators (premorbid social adjustment, number of hospitalizations and global assessment of functioning) were significantly related to non-FRS scores (p < 0.006) but not to FRS scores (p > 0.05). Furthermore, no validator was significantly related to FRS scores and unrelated to non-FRS scores, all of which indicates an overall better predictive validity for non-FRS delusions and hallucinations. These findings suggest that FRS do not have diagnostic value for diagnosing schizophrenia and that they do not meaningfully add to the external validity showed by other delusions and hallucinations. We believe that much of the misunderstanding about the diagnostic and clinical validity of FRS for schizophrenia is rooted in Schneider's confusing concept of the disorder.

Kurt Schneider introduced in the definition of the first-rank symptoms (FRS) the criterion that, where unequivocally present, the FRS are always psychological primaries and irreducible. This criterion, grounded on ‘phenomenology’ (description of subjective experiences), cannot be applied, according to Schneider, to delusions, either two-stage FRS delusional perception, or second-rank delusional notions. The Schneider's key criterion was neglected since the initial adoption of the ‘Schneider's FRS’ in the subsequent international literature (e.g. PSE, RDC, DSM, and ICD). The ‘Schneider's FRS’ (e.g. thought insertion, thought withdrawal, passivity, and influence) were persistently equivocated as ‘delusions’, in spite of the Schneider's FRS exclusion criterion. The internationally equivocated ‘Schneider's FRS’ (only homonymous of the original ‘Schneider's FRS’), were eliminated in the DSM-5 and de-emphasized in ICD-11. However, the diagnostic value of the original ‘Schneider's FRS’, assessed on the basis of the strict compliance with the Schneider's criterion for their definition, was never determined. The ‘damnatio memoriae’ of the original Schneider's FRS may be premature. The definition and assessment of the ‘experienced’ symptoms of schizophrenia, only directly observed and reported by the patients, represent a specific, crucial, irreplaceable domain of psychopathology, to be carefully distinguished from the domain of the ‘behavioral’ symptoms observed by the clinician. Contemporary psychopathology research is aware of the absolute need for psychiatry to enhance precision and exactness in the definition of the experienced symptoms of schizophrenia, through the formulation of unequivocal inclusion and exclusion criteria (descriptive micro-psychopathology), in order to determine their value in research and care.