Origins and early development of the case-control study: Part 1, Early evolution.

This paper traces the origins and early development of the case-control study, focusing on its evolution in the 19th and early 20th century. As with other forms of clinical investigation, the case-control study emerged from practices that originally belonged to the realm of patient care. This form of disease investigation can be viewed as the knitting together of medical concepts (caseness, disease etiology, and a focus on the individual)--and medical procedures (anamnesis, grouping of cases into series; and comparisons of the diseased and the healthy)--that are of ancient origin, but which were seldom brought together until the 20th century. The analytic form of the case-control study can be found in 19th century medical literature, but did not appear to be viewed as a special or distinct methodology. A number of clinical investigations, and several sociological studies, in the first half of this century can be described as case-control studies, the most fully developed of which was Janet Lane-Claypon's 1926 study of breast cancer.