Previous epidemiological studies have generally shown an increased prevalence of schizophrenic disorders among lower socioeconomic status (SES) individuals, but the mechanism mediating this relationship has been unclear. Hypotheses that have been proposed include: a tendency for schizophrenics to move downward in the social hierarchy, the "downward drift hypothesis"; an increased schizophrenic gene pool in lower SES strata; and a provocative or inductive effect on psychopathology produced by factors associated with lower SES membership.
Naturalistic studies do not allow a separation of possible genetic and environmental indicators. To circumvent this problem, we studied these relationships in adopted populations. The findings of this study support only the downward drift hypothesis. The special attributes of this study population and the possible biases it may have introduced are discussed.
Wender PH, Rosenthal D, Kety SS, Schulsinger F, Welner J. Social Class and Psychopathology in AdopteesA Natural Experimental Method for Separating the Roles of Genetic and Experiential Factors. Arch Gen Psychiatry. 1973;28(3):318-325. doi:10.1001/archpsyc.1973.01750330020003