The evolution of some European diagnostic concepts relevant to the category of schizoaffective psychoses.

The evolution of the German-Scandinavian concept of cycloid psychosis and of the French concept of 'bouffée délirante' is analyzed. It is stressed that they probably correspond to the same clinical entity, not overlapping with any of the American nosological categories, although sharing a number of features with the original Kasanin's picture of schizoaffective psychosis. Moreover, a survey is given of the evidence supporting the construct and predictive validity of the concept of cycloid psychosis.