Dutch Study: Schizophrenia Risk Higher in Mixed Neighbourhoods

Migrants in the Netherlands who live in neighbourhoods with a mixed Dutch-migrant population run a higher risk of developing schizophrenia than those in migrant-only neighbourhoods, according to a Dutch study published on Monday.

The study, published in the American Journal of Psychiatry, was conducted among so-called first and second generation migrants in several neighbourhoods of The Hague.

Some of the neighbourhoods had a mixed population, while others were migrants only.

Researcher Wim Veling of Dutch mental health care provider Parnassia Navo Group found that the chances of developing schizophrenia doubled for Surinamese and Turks and multiplied by four for Moroccans if they lived in mixed Dutch-migrant residential areas.

It has been known for a while that immigrants run a higher risk of developing schizophrenia than locals.

However, Veling argues that there is a link between the disease and the frequency with which migrants are confronted with locals.

Discrimination may increase the stress exposure of migrants, according to Veling.

He also found that the difficulties young people encounter in developing their own identity while living in mixed ares might increase the chances of schizophrenia.

Schizophrenia is a mental illness characterized by impairments in the perception or expression of reality, and might include symptoms such as auditory hallucinations, paranoid or bizarre delusions or disorganized speech and thinking.

First symptoms usually occur during young adulthood.

[Editor’s Note: “Ethnic Density of Neighborhoods and Incidence of Psychotic Disorders Among Immigrants,” by Wim Veling, et al., can be read or downloaded as a PDF document here. A subscription to American Journal of Psychiatry Online is required. The abstract appears below.]

Wim Veling, M.D., Ezra Susser, M.D., Dr.Ph., Jim van Os, M.D., Ph.D., Johan P. Mackenbach, M.D., Ph.D., Jean-Paul Selten, M.D., Ph.D., and Hans W. Hoek, M.D., Ph.D.

Objective: A high incidence of psychotic disorders has been reported in immigrant ethnic groups in Western Europe. Some studies suggest that ethnic density may influence the incidence of schizophrenia. The authors investigated whether this increased incidence among immigrants depends on the ethnic density of the neighborhoods in which they live. Method: This was a prospective first-contact incidence study of psychotic disorders in The Hague, by ethnicity and neighborhood of residence. Over a 7-year period, individuals who made contact with a physician for a suspected psychotic disorder underwent diagnostic interviews and received DSM-IV diagnoses. A comprehensive municipal registration system provided the denominator for incidence rates. Data were sufficient to examine incidence rates in native Dutch and in first- and second-generation immigrants from Morocco, Suriname, and Turkey. The ethnic density of a neighborhood was computed for each immigrant group as the proportion of residents belonging to that group. Multilevel regression analyses predicted the incidence of psychotic disorders as a function of individual ethnicity and neighborhood ethnic density. Models were fitted for all immigrants together and for each immigrant group separately. Results: A total of 226 native Dutch and 240 immigrants were diagnosed as having a psychotic disorder. Compared with native Dutch, the adjusted incidence rate ratio for immigrants was significantly increased in low-ethnic-density neighborhoods (2.36) but not in high-ethnic-density neighborhoods (1.25). There was a strong interaction between individual ethnicity and neighborhood ethnic density as predictors of incidence of illness. These findings were consistent across all immigrant groups. Conclusions: The incidence of psychotic disorders was elevated most significantly among immigrants living in neighborhoods where their own ethnic group comprised a small proportion of the population.