The symptoms of schizophrenia span a wide range of psychopathology and display an extraordinary amount of interindividual and temporal variability. Over time, authors have invested different diagnostic value to symptoms, depending on their theoretical point of view. For Emil Kraepelin, dementia praecox was a nosological entity and the negative symptoms—Verblödung—were characteristic; for Eugen Bleuler, schizophrenia was a heterogeneous syndrome and thought disorders were the distinctive feature; and for Kurt Schneider, schizophrenia was a diagnostic convention and certain disturbances of the experience—the so-called first-rank symptoms—were the defining features.
Cuesta MJ, Peralta V. Going Beyond Classic Descriptions to Future Phenomenology of Schizophrenia. JAMA Psychiatry. 2016;73(10):1010-1012. doi:10.1001/jamapsychiatry.2016.2126