A critical review of recent adoption, twin, and family studies of schizophrenia: behavioral genetics perspectives.

Continuing uncertainty about the etiology of schizophrenia calls for periodic reappraisal of relevant data and conclusions, reappraisals guided by a beacon of modest doubt to avoid the distorted views of both the zealot and the skeptic. This review does not set out to cover every possible aspect of the genetics of schizophrenia. It deals with data from recent family, twin, and adoption studies of schizophrenia rather than with theoretical issues—data primarily selected because they provide grist for one or another genetically "powered" mills. The conference entitled "The Transmission of Schizophrenia," held at Dorado Beach, Puerto Rico, in 1967 (Rosenthal and Kety 1968) is our point of departure, since it was there that the first reports were given of the adoption studies carried out in Denmark by Rosenthal, Kety, Wender, Schulsinger, and their colleagues (Kety et al. 1968 and Rosenthal et al. 1968). This is not to say there was no credible evidence in favor of genetic influences in schizophrenia before the adoption studies