## Kinds versus continua: a review of psychometric approaches to uncover the structure of psychiatric constructs - summary of an article by Borsboom, Rhemtulla, Cramer, van der Maas, Scheffer and Dolan

Critical thinkingArticle: Borsboom, Rhemtulla, Cramer, van der Maas, Scheffer and Dolan (2016)Kinds versus continua: a review of psychometric approaches to uncover the structure of psychiatric constructsThe present paper reviews psychometric modelling approaches that can be used to investigate the question whether psychopathology constructs are discrete or continuous dimensions through application of statistical models. The question of whether mental disorders should be thought of as discrete categories or as continua represents an important issue in clinical psychology and psychiatry.The DSM-V typically adheres to a categorical model, in which discrete diagnoses are based on patterns of symptoms.But, such categorizations often involve apparently arbitrary conventions. All measurement starts with categorization, the formation of equivalence classes.Equivalence classes: sets of individuals who are exchangeable with respect to the attribute of interest.We may not succeed in finding an observational procedure that in fact yields the desired equivalence classes.We may find that individuals who have been assigned the same label are not indistinguishable with respect to the attribute of interest.Because there are now three classes rather than two, next to the relation between individuals within cases (equivalence), we may also represent systematic relations between members of different cases.One may...

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