DESCRIPTION (provided by applicant): Linkage disequilibrium (LD) analysis has been shown to be an ideal method for mapping complex disease genes in isolated founder populations. This application is designed to collect a sample of patients with schizophrenia who are descended from the founder population of Costa Rica, with the goal of mapping and identifying schizophrenia predisposition genes in this country. The Costa Rican population is ideal for this study, because it is a large population descended over 20 generations from a small group of founders, and predisposition genes for bipolar affective disorder have already been mapped in this country. Our sample consists of Costa Rican patients with multiple hospitalizations for acute schizophrenic episodes and with early age of onset. Diagnostic procedures include a blinded interview by a bilingual psychiatrist, using the DIGS (Diagnostic Interview for Genetic Studies), as well as a family history interview, semi-structured collection of medical records, and a best-estimate process. Genealogic workup is done for each proband to document birthplace of ancestors in the great-grandparents' generation. The goal of this next phase of the study is to recruit additional schizophrenic probands who meet the following criteria: 1) DSM-IV consensus diagnosis of schizophrenia; 2) two or more psychiatric hospitalizations; 3) ancestry from central valley of Costa Rica; and 4) age of onset prior to age 40. Our hope is to collect information on several subtypes of schizophrenia, such as paranoid, undifferentiated and schizoaffective types. DMA samples will be collected from probands and parents, to allow for dense genome wide association analysis. Additional genomic analyses will be performed across schizophrenic candidate regions identified in this or other populations. Relevance to public health: Schizophrenia is a severe, disabling psychiatric condition which affects approximately 2.5 million Americans. Schizophrenia is a brain disorder, and this illness is thought to be inherited. This grant aims to identify the genes which contribute to causing schizophrenia. By identifying the genes which contribute to the diagnosis of schizophrenia, scientists will be able to better diagnose and treat this disabling illness.