Diagnostic issues in Moroccan immigrants to the Netherlands

Incidence of schizophrenia among migrants in the Netherlands: a direct comparison of first contact and longitudinal register approaches

PURPOSE

To estimate the effect of selective sampling on first contact (FC) studies of the relation between migration and schizophrenia.

METHODS

We compared the FC method directly with a more inclusive longitudinal psychiatric register (LPR) method, by letting both methods estimate age and sex adjusted incidence rate ratios (IRR) in the population of The Hague aged 20-54 years, for the three largest migrant groups (first and second generation Caribbean, Turkish, and Moroccan) relative to the native Dutch population.

RESULTS

Both methods found that the adjusted IRR was higher for migrants than for native Dutch [all migrants IRR = 1.70 (95% Cl 1.30-2.21) for the LPR method and 1.91 (95% Cl 1.15-3.25) for the FC]. The IRR for Moroccans was significantly lower in the LPR [IRR 2.69 (95% 2.10-3.41)] than in the FC study [4.81 (3.41-6.68)]. The FC method was relatively more inclusive for migrants presenting at earlier ages or with shorter durations of prior treatment (DPT) than the native Dutch. This resulted in differential sampling and artificially higher IRRs for Moroccan and, to a lesser extent, Turkish migrants.

CONCLUSION

We confirm that the incidence of schizophrenia is raised twofold for migrants compared to nonmigrants. Using the LPR method, however, IRR estimates were less pronounced for most migrant groups than in a high quality FC study conducted in the same population. The FC method may overestimate the risk of schizophrenia for migrant groups who seek first mental health at a relatively younger age, or who present directly with schizophrenia.

Effects of a culturally sensitive assessment on symptom profiles in native Dutch and Moroccan patients with a first psychosis referral

Previous studies have reported a higher incidence of psychosis in Moroccan immigrants in the Netherlands than among native-born residents. However, this disparity was substantially attenuated when cultural differences in symptom presentation were taken into account. To better understand the impact of different diagnostic procedures on incidence rates, we examined the effects of the use of a culturally sensitive diagnostic interview, compared to a standard semi-structured diagnostic interview, on symptom profiles among Moroccan immigrant and native Dutch patients in the Netherlands. A total of 26 Dutch and 26 Moroccan patients referred with a possible first psychosis diagnosis were interviewed twice: once with the standard version and once with a culturally adapted version of the Comprehensive Assessment of Symptoms and History questionnaire (CASH and CASH-CS, respectively). Among native Dutch patients, symptoms profiles based on CASH and CASH-CS interviews were very similar. By contrast, among Moroccan immigrant patients, symptom profiles based on CASH and CASH-CS interviews differed substantially, with more mania symptoms (+30%; p < .05) and fewer delusions (-31%; p < .05) reported when using the CASH-CS. These results suggest that the over-diagnosis of schizophrenia in Moroccan immigrants with a first psychosis referral may be related to a tendency to under-detect mood symptoms and over-detect positive psychotic symptoms when a standard diagnostic procedure is used. This bias may be corrected, at least in part, by the use of a culturally sensitive interview instrument such as the CASH- CS.