Individuals were collected through 12 clinical collaborating sites across the United States. All individuals ascertained to the GPC completed a screening questionnaire eliciting demographic (e.g., race, ethnicity, gender) data as well as a brief personal and family psychiatric and medical history. Individuals with psychotic illness were ascertained as in-patients in acute care or chronic care facilities, and out-patient settings. Control subjects were drawn from the same geographic area as cases, either within health care facilities or as community volunteers recruited from internet advertising or community groups (e.g. church congregations, health fair attendees) and screened to ensure absence of schizophrenia or bipolar disorder within themselves and their first degree relatives.
