a major psychotic disorder (e.g., schizophrenia or schizoaffective disorder) were excluded from the study. We also recruited other siblings and parents whenever available regardless of their affection status to increase the power to detect linkage. Each subject provided written informed consent prior to participation. We complied with the Code of Ethics of the World Medical Association (Declaration of Helsinki). The institutional review board at each site approved the study, and certificates of confidentiality for the work were issued by the National Institute on Drug Abuse and the National Institute on Alcohol Abuse and Alcoholism.
