The British Journal of Psychiatry
The identification of disease entities and the relationship between schizophrenic and affective psychoses.
R E Kendell, I F Brockington

Abstract

A method is described for identifying a genuine boundary between related syndromes, if one exists, by demonstrating a non-linear relationship between symptomatology and outcome. The technique was applied to the putative boundary between schizophrenic and affective psychoses, but a non-linear relationship could not be demonstrated.