[Quantification in psychiatry: from psychometrics to quantitative psychiatry]

The development of quantitative techniques to analyse psychopathological states is reviewed from the XVIIIth Century till today. As far as back as the XIXth Century, Quetelet, Louis and Galton introduced and advocated the use of quantitative methods in medical and psychological sciences. The advent of psychometry dates back 1905, when Alfred Binet published his Intelligence Scale. The construction of instruments like Wechsler and MMPI scales in the forties starts using psychometry in psychiatry. At end of World War II, historical factors (selection and guidance of military recruits) in conjunction with technical advancements (beginning of psychopharmacology, multivariate statistics development and first computers arrival) favor the growth of quantitative psychopathology that further takes four great different courses: 1. Psychometry proper, 2. Symptom-quantifying assessment scales such as BPRS or Hamilton scales, 3. New nosological models constructed using quantified psychopathological data and mathematical procedures, 4. Diagnostic systems relying on operationalized criteria based on psychopathological quantification, such as DSM III.