The sample for de novo CNV analysis comprised 662 Bulgarian parent–proband trios from 638 families. We did not exclude probands (N=61) with a history of psychosis in a parent as none of the risk CNVs identified to date are sufficiently penetrant to fully explain the disorder in carriers. All cases had been hospitalised and met DSM-IV (Diagnostic and Statistical Manual of Mental Disorders-fourth edition) criteria for schizophrenia or schizoaffective disorder based upon SCAN (Schedules for Clinical Assessment in Neuropsychiatry) interview by psychiatrists, and review of case notes. Cases were recruited from general adult psychiatric services and were typical of those attending those services. Although they did not have formal IQ assessments, all attended mainstream schools from which people with known mental retardation were excluded. All participants provided informed consent. Further details concerning ascertainment and diagnostic practices are provided in the Supplementary Material. All DNA samples were derived from peripheral venous blood.
