The prevalence of schizophrenia in relatives of schizophrenic patients

This study examines the prevalence of schizophrenia in 871 first-degree relatives of schizophrenic probands (N = 121) and 658 first-degree relatives of age-matched controls. The controls (N = 126) were medical inpatients referred for psychiatric opinion in a general hospital. Diagnoses in the probands fulfilled the ICD criteria for schizophrenic psychoses. Information on the relatives were obtained from enquiry of the family history and the hospital case records. The prevalence of schizophrenia in first-degree relatives of schizophrenic probands was 22 times that of the medical controls (6.8% versus 0.3%) (p < 0.05). The result supports the observation that schizophrenia is a familial disorder.