Rural-urban variation in incidence of psychosis in France: a prospective epidemiologic study in two contrasted catchment areas

BACKGROUND: The aim of our study is to provide data on the incidence of psychotic disorders in France and compare the incidence rates in populations with different levels of urbanization. METHODS: We prospectively included the incident cases of psychotic disorders from two catchment areas with contrasted levels of urbanization. In the more rural area, we also calculated incidence rates in three different groups of population defined by the size of towns in which they live (small, medium and large towns). RESULTS: The annual incidence of psychosis was greater in the urban area (36.02/100000 person-year at risk) than in the rural area (17.2/100000 person-year at risk). Non-affective psychoses were the majority of cases and their incidence was greater in males and younger subjects. The affective psychoses were slightly more frequent in women and showed less variation with age. In the rural centre, greater levels of urbanicity were associated with an increase in the incidence of all psychoses (affective and non-affective). CONCLUSIONS: Our study confirms previous observations of increased incidence rates for non-affective psychoses in the more urbanized areas and suggests that a similar pattern might be present for affective psychoses.