summary
background Research into the risk factors for schizophrenia has once again drawn attention to the geographical differences in the incidence and gender distribution of schizophrenia. The incidence - as recorded by the mental health care services - of non-affective psychotic disorders in the Netherlands is unknown.
aim To ascertain the mental-health-care recorded incidence of non-affective psychotic disorders in Friesland and Twente in 2002.
method The medical files of all adults who made their first contact with mental health care services in 2002 (n = 6477) via two clinics in the Netherlands were screened for psychotic symptoms. All patients with psychotic symptoms (n = 242) were included and the clinical diagnosis was recorded. Thirty months later the most recent clinical diagnosis was recorded again.
results Within six months of their first contact 75 patients were diagnosed with nonaffective disorder. This diagnosis was still valid after 30 months. These results demonstrate an incidence of 2.2/10,000 inhabitants. The male-female ration was 1.8:1. The incidence of psychotic disorder did not differ significantly between the two regions under study.
conclusion The incidence found corresponds to the incidence reported in earlier Dutch studies; it lies on the 75th percentile of the cumulative incidence given in an international review.