The high incidence of psychiatrically treated disorders in the inner city of Mannheim. Susceptibility of German and foreign residents.

In earlier investigations in the city of Mannheim we examined the spatial distribution of the incidence of treated mental disorders in 1965 and 1974-80. In studying the ecology of psychiatric disorders over time, it is important to consider major demographic developments. In Mannheim between the mid-sixties and 1980 the most striking demographic change was the increase of foreign residents, whose proportion almost trebled during this period. In this study we test the hypothesis whether the excess morbidity in the inner city where housing conditions are relatively poor and the percentage of foreign residents is far above average can be explained by the high proportion of immigrants, mainly from Turkey, living there. Due to motivational and administrative factors, most immigrant workers being recruited on the basis of good physical and mental health, the age-adjusted incidence of treated psychiatric disorders between 1974 and 1980 among the German population exceeded that of foreign residents. The high concentration of psychiatric disorders in the inner city is due solely to the German and not to the foreign residents. The most plausible explanation for this is provided by the segregation hypothesis. Individuals with vulnerable personalities tend to move to socially disorganized districts of the city. Furthermore, the health status of those Germans who left areas of poor environmental conditions was probably better in comparison to those who remained in the inner city.