All participants were recruited in accordance with the principles of the Declaration of Helsinki and with approval from the Institutional Review Boards of each participating site, as part of a family based linkage study of SC and schizoaffective disorder. Recruitment teams were located in San Antonio (Texas, US), Los Angeles and San Diego (California, US), Monterrey and Mexico City (Mexico), Guatemala City (Guatemala), and San José (Costa Rica). All sites participated in group training sessions to standardize assessments using the Diagnostic Interview for Genetic Studies (DIGS) (Nurnberger et al., 1994), the Family Interview for Genetic Studies (FIGS) (Maxwell, 1992), and a review of psychiatric records. Families were eligible for study if they had at least two siblings with hospital or clinical diagnoses of SC or schizoaffective disorder. Subjects included in the study were all over 18 age of year, willing to contribute a blood sample, and complete a diagnosis interview. Subjects were recruited if their parents had ancestry from Central America or Mexico. Subjects were also asked to describe their parents’s ethnicity, as part of the DIGS interwiew (see description in Results). After complete description of the study to the subjects, written informed consent was obtained.
