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

Abstract

PurposeTo estimate the effect of selective sampling on first contact (FC) studies of the relation between migration and schizophrenia.MethodsWe 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.ResultsBoth 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.ConclusionWe 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.Electronic supplementary materialThe online version of this article (doi:10.1007/s00127-016-1310-8) contains supplementary material, which is available to authorized users.

Estimating the incidence of first-episode psychosis using population-based health administrative data to inform early psychosis intervention services

“…Similar to our findings, known risk factors for psychotic disorder, such as gender and ethnic minority status, are attenuated when using a longitudinal v. a first contact sampling frame (Hogerzeil et al ., 2014, 2017), although our findings suggest greater disparities by neighborhood income quintile for a longitudinal sampling frame, which has not been reported previously. This raises the question of the extent to which the evidence on these well-established risk factors for psychotic disorder may have been conflated with factors that impact on access to specialized psychiatric services.…”

The epidemiological burden of major psychiatric disorders

“…the WHO ten-country study, the AESOP study), or lifetime prevalence estimates from cross-sectional surveys. This pattern has been recently noted by Hogerzeil et al [34,35], using a dual firstcontact and register-based design in the same population. Several reasons for this discrepancy may exist, but register-based designs may be more comprehensive in case identification, as 'hospital' registers will typically identify all people diagnosed with a disorder in a given healthcare system, including both in-and outpatient facilities.…”

Women who suffer from schizophrenia: Critical issues

“…Further theoretical possibilities for prevention (based entirely on studies of association) are keeping children in their country of birth, since migration is a risk factor for schizophrenia[ 30 , 31 ], residing in rural rather than urban parts of the country[ 32 , 33 ], keeping children and adolescents away from alcohol and drugs[ 34 ] and teaching them emotion-regulating strategies (reappraising, accepting, and refocusing[ 35 ]) to prevent adversities such as discrimination and social defeat from culminating in paranoid delusions[ 36 ].…”