Patients with schizophrenia were defined as individuals identified in the Hospital Discharge Register having at least two inpatient hospitalizations with a discharge diagnosis of schizophrenia (ICD-8 295, ICD-9 295, ICD-10 F20, with latent schizophrenia, 295.5 and 295F, excluded.). The criterion of at least two inpatient hospitalizations was chosen to increase diagnostic precision and provided in a previous study nearly identical estimates of familial risks to those from the literature22.
