This book is a collective work draws on the perspective of social sciences, mobilizing perspectives from the sociology of science, the history of psychiatry, medical ethnography and public policy analysis. This initiative, which has no precedent in social sciences, is surrounded by an original, if not apparently paradoxical statement: considering that the deployment of these processes, strictly formal and depersonalized, is justified in becoming the rule in a society known as "individuals". Presents the measurement of mental disorders (tests / scales) across the various sectors Determines the underpinning of this measure and its performance Explains the rise of these tests and its success Understands its impact on users