This article investigates the redefinition of depression that took place in the early 1970s. Well before the introduction of the third edition of the Diagnostic and Statistical Manual of Mental Disorders, this rather rare and severe psychiatric disorder hitherto treated in asylums was transformed into a widespread mild mood disorder to be handled by general practitioners. Basing itself on the archives of the Swiss firm Ciba-Geigy, the article investigates the role of the pharmaceutical industry in organizing this shift, with particular attention paid to research and scientific marketing. By analyzing the interplay between the firm, elite psychiatrists specializing in the study of depression, and general practitioners, the article argues that the collective construction of the market for first-generation antidepressants triggered two realignments: first, it bracketed etiological issues with multiple classifications in favor of a unified symptom-oriented approach to diagnosis and treatment; second, it radically weakened the differentiation between antidepressants, neuroleptics, and tranquilizers. The specific construction of masked depression shows how, in the German-speaking context, issues of ambulatory care such as recognition, classification, and treatment of atypical or mild forms of depression were reshaped to meet commercial as well as professional needs.