[Nosological status of the intermediate area between schizophrenia and affective disorder]

Non-organic psychoses diagnosed with neither schizophrenia nor affective disorder are an aggregation of heterogeneous psychotic disorders including major groups such as acute polymorphic psychotic disorders and schizoaffective disorders. Historically, similar psychotic pictures have been reported in various cultures. However, their slightly different definition hindered comparative studies. Even after the establishment of an operational diagnostic guideline such as ICD-10, epidemiological studies on this intermediate area between schizophrenia and affective disorder have brought different findings, making the reliability of diagnosis of this area questionable. Moreover, the situation is further complicated that there exists not only cases which have repeated the same episode as the first, but also cases whereby the diagnosis has been changed to schizophrenia or affective disorder over a long-term course. K. Schneider, who suggested not differential diagnosis but differential typology in the area of endogenous psychoses, is right in thinking of the existence of this intermediate area. We should be satisfied with making a provisional diagnosis, should take a flexible attitude towards changes in diagnosis between episodes. And during diagnosis, we should not differentiate schizophrenia from affective disorders rigidly, nor define the intermediate area strictly.