Generally, psychotic disorders appear to be very heterogenous among different locations (Jongsma, Turner, Kirkbride, & Jones, 2019), especially for minorities. However, it is unknown how the incidence pattern for these groups varies within the European continent. Previous research has showcased an increased incidence of affective and non-affective psychotic disorders in Western Europe for migrant and minority ethnic groups (Bourque, van der Ven, & Malla, 2011; Selten, van der Ven, & Termorshuizen, 2020).
The aim of this particular study by Termorshuizen et al. (2020) was to compare the incidence rates and incidence rate ratios of psychotic disorders for minorities across various locations in Europe.
The authors analysed data from the European Network of National Schizophrenia Networks Studying Gene–Environment Interactions (EU-GEI) study, which was conducted between 2010 and 2015.
To test their hypothesis, they assessed whether there are differences in the incidence rates and incidence rate ratios (IRRs) across 13 recruitment sites located in France, Italy, Spain, the Netherlands and the UK. For the purpose of this study, minorities are defined as being of migrant and/or minority ethnic group descent. Religious or sexual minorities were not considered. The term ‘reference population’ refers to all other citizens. Minorities were divided in seven subgroups by region of origin as follows: 1. Western countries; 2. Middle East 3; The Maghreb; 4. sub-Saharan Africa; 5. Asia; 6. Latin America and 7. The Caribbean islands.
Categories 2 to 7 were operationally defined as non-Western migrants. All participants were individuals 18–64 years of age who resided within the catchment areas and presented to mental health services for a suspected first episode of psychosis. The primary outcome was a confirmed ICD-10 diagnosis of any psychotic disorder. The broad category of any psychotic disorder was subdivided into non-affective (NAPD) and affective psychotic disorder (APD). The authors estimated the incidence per 100,000 person years by site for minorities and the reference population. Incidence was analysed using Poisson regression models for minorities altogether and separately for the seven subgroups. Factors of age, gender, ethnic minority status and recruitment site were adjusted for.
The results of this study are characterised by large variation. The analyses include 1,886 cases with any psychotic disorder, comprised of 775 from minorities and 1,111 from the reference populations. Among the various sites where data was accumulated the standardised incidence rates for minorities ranged from 12.2 in Valencia to 82.5 per 100.000 people in Paris. For most sites, IRRs were higher for persons from non-Western countries than for those from Western countries, with the highest IRRs for individuals from sub-Saharan Africa. These rates were generally high at sites with high rates for the reference population, and low at sites with low rates for the reference population. Results were consistent for both APD and NAPD.
In simple words, the rates in minorities illustrated a clear pattern of increased incidence for minorities overall, more increased for persons from non-Western countries and most increased for individuals from sub-Saharan Africa.
The authors concluded that incident rates of psychosis varied by region of origin, region of destination and the combination of the two. This suggests that social context can be a driving force for this attribution.
Strengths and limitations
Overall, the authors have made a great contribution to our understanding of the incidence of psychotic disorders in a well conceptualised and sound scientific manner. Using the data of one of the first studies to compare psychosis incidence rates among minorities across several countries using a uniform methodology (Jongsma et al., 2018). This new information has the potential to open new pathways and help shape a solid understanding of the prevalence and aetiology of psychosis.
However there were significant limitations. From my point of view, the biggest drawback is the operational definition of minorities. The authors used two different definitions for the minority: one based on self-assigned ethnicity (for the UK) and another on migration history. Since the large ethnic minority groups in Europe do have a recent migration history, most members are also first or second-generation migrants. This makes it tricky as where to draw the line in order for someone to be able to identify with the “reference population”. Hence, length of family history may function as a confounding variable, while relying on self-report may lead to some individuals changing their response due to social desirability in order to fit in. As per the researchers, this caused some degree of confusion in sorting out data coming from France, Italy and Spain where one cannot distinguish between second-generation migrants and the native-born population.
Furthermore, the subgroups that the authors finally decided upon refer to a very large portion of the population that are highly heterogeneous. Substantial differences in language, culture and socioeconomic status among people within them raise concerns about the generalisability of the findings. This variability extends to differences in regional mental health service differences. This could influence the probability of mental health care utilisation, especially among individuals who face additional linguistic and cultural barriers (Lindert, Schouler-Ocak, Heinz, & Priebe, 2008).
Implications for practice
These findings add to the existing literature, which suggests that first and second generation migrants in Europe are susceptible to more risks overall (Selten et al., 2020). The inter-site elevated incidence rates in comparison to the reference population indicate that their risk is not a fixed quantity independent from the environment. From a psychosocial outlook, the elevated risk of developing psychotic symptoms may stem from the greater exposure to social risk that minorities may be exposed to over their life course. For instance, threat, hostility and violence (Morgan, Knowles, & Hutchinson, 2019), as well as a higher ratio of untreated to treated cases of major mental disorder (Link & Dohrenwend, 1980).
Hence, future studies can potentially strive to investigate these potential socioeconomic influences besides strictly a factor of origin. These can revolve around gender, level of education, income, employment status, as well as belonging to other religious and sexual minority groups. Additionally elaborating more in depth upon this data per specific location can also be indicative. The authors conclude and could not have said better that ultimately this can lead to tailored and site-specific interventions and may also give insight into protective factors that help persons from minority populations to cope with exposure to high risk.
Conflicts of interest
Termorshuizen, F., Van der Ven, E., Tarricone, I., Jongsma, H., Gayer-Anderson, C., Lasalvia, A., . . . Selten, J. (2020). The incidence of psychotic disorders among migrants and minority ethnic groups in Europe: Findings from the multinational EU-GEI study. Psychological Medicine, 1-10. doi:10.1017/S0033291720003219
Bourque, F., van der Ven, E., & Malla, A. (2011). A meta-analysis of the risk for psychotic disorders among first- and second-generation immigrants. Psychological Medicine, 41(5), 897–910. doi: 10.1017/S0033291710001406
Jongsma, H. E., Gayer-Anderson, C., Lasalvia, A., Quattrone, D., Mule, A., Szoke, A., … European Network of National Schizophrenia Networks Studying Gene-Environment Interactions Work Package, Group. (2018). Treated inci- dence of psychotic disorders in the multinational EU-GEI study. JAMA Psychiatry, 75(1), 36–46. doi: 10.1001/jamapsychiatry.2017.3554
Jongsma, H. E., Turner, C., Kirkbride, J. B., & Jones, P. B. (2019). International incidence of psychotic disorders, 2002-17: A systematic review and meta-analysis. Lancet Public Health, 4(5), e229–e244. doi: 10.1016/ S2468-2667(19)30056-8
Lindert, J., Schouler-Ocak, M., Heinz, A., & Priebe, S. (2008). Mental health, health care utilisation of migrants in Europe.European Psychiatry, 23(Suppl 1), 14–20. doi: 10.1016/S0924-9338(08)70057-9
Link, B., & Dohrenwend, B. P. (1980). Formulation of hypotheses about the ratio of untreated to treated cases in the true prevalence studies of functional psychiatric disorders in adults in the United States. In B. P. Dohrenwend, B.S. Dohrenwend, M.S. Gould, B. Link, R. Neugebauer & R. Wunsch-Hirzig (Eds.), Mental illness in the United States: Epidemiological estimates (pp. 133–148). New York: Praeger.
Morgan, C., Knowles, G., & Hutchinson, G. (2019). Migration, ethnicity and psychoses: Evidence, models and future directions. World Psychiatry, 18(3), 247–258. doi: 10.1002/wps.20655
Selten, J. P., van der Ven, E., & Termorshuizen, F. (2020). Migration and psychosis: A meta-analysis of incidence studies.Psychological Medicine, 50(2), 303–313. doi: 10.1017/S0033291719000035