Testing Ødegaard's selective migration hypothesis: a longitudinal cohort study of risk factors for non-affective psychotic disorders among prospective emigrants

Review of Major Social Determinants of Health in Schizophrenia-Spectrum Disorders: II. Assessments

BACKGROUND AND AIMS

Social determinants of health (SDoHs) impact the development and course of schizophrenia-spectrum psychotic disorders (SSPDs). Yet, we found no published scholarly reviews of psychometric properties and pragmatic utility of SDoH assessments among people with SSPDs. We aim to review those aspects of SDoH assessments.

STUDY DESIGN

PsychInfo, PubMed, and Google Scholar databases were examined to obtain data on reliability, validity, administration process, strengths, and limitations of the measures for SDoHs identified in a paired scoping review.

STUDY RESULTS

SDoHs were assessed using different approaches including self-reports, interviews, rating scales, and review of public databases. Of the major SDoHs, early-life adversities, social disconnection, racism, social fragmentation, and food insecurity had measures with satisfactory psychometric properties. Internal consistency reliabilities-evaluated in the general population for 13 measures of early-life adversities, social disconnection, racism, social fragmentation, and food insecurity-ranged from poor to excellent (0.68-0.96). The number of items varied from 1 to more than 100 and administration time ranged from less than 5 minutes to over an hour. Measures of urbanicity, low socioeconomic status, immigration status, homelessness/housing instability, and incarceration were based on public records or targeted sampling.

CONCLUSIONS

Although the reported assessments of SDoHs show promise, there is a need to develop and test brief but validated screening measures suitable for clinical application. Novel assessment tools, including objective assessments at individual and community levels utilizing new technology, and sophisticated psychometric evaluations for reliability, validity, and sensitivity to change with effective interventions are recommended, and suggestions for training curricula are offered.

Risk of psychosis among migrants to the Netherlands by time since arrival

BACKGROUND

The high risk of psychosis among migrants is often attributed to social stressors in the host country. We examined whether the relative risk of psychosis among migrants is low on arrival and increases thereafter.

METHODS

In this cohort study, first-generation immigrants to the Netherlands, aged 10 years and older (N = 1 281 678), were matched by birth year and sex to 2 542 313 native-born Dutch controls. The first occurrence of psychosis after arrival was established using data on dispensing of antipsychotic medication (APM) (during 2006-2017) and on insurance claims for treatment of psychosis (2011-2016). The Incidence Rate Ratios (IRRs) for migrants compared to controls were estimated by year since arrival.

RESULTS

The IRR of APM was 0.22 (95% CI 0.21-0.24) in the year of arrival ('year 1') and increased gradually to 1.39 (1.19-1.62) after 10 or more years. The IRR of an insurance claim increased from 0.57 (0.51-0.62) to 1.87 (1.38-2.55) in year 5. Among migrants from sub-Saharan Africa, the IRR of an insurance claim was already high in year 1 [2.46 (1.95-3.11)], especially when aged 10-20 years at arrival [6.09 (2.93-12.64)]. Among migrants from other non-Western countries, the IRR was already significantly increased in year 2 [1.28 (1.03-1.59)].

CONCLUSIONS

The relative risk of psychosis among migrants was generally low at arrival and increased thereafter. The increased IRRs in the early years after arrival among those from non-Western countries indicate that for these groups certain risk factors are already relevant shortly after arrival.

Traumatic experiences in childhood and adolescence: a meta-analysis of prospective studies assessing risk for psychosis

Evidence of the association between traumatic experiences and psychosis are uncertain with respect to temporal order, clinical outcomes and the role of the age and genetic liability. The aim of the present meta-analysis was to explore the temporal relationship between the development of psychosis and traumatic exposure using prospective studies and to examine the role of moderation factors on overall effect sizes. Studies were identified by searching Embase-Ovid, PsycINFO (EBSCO), Pubmed, Scopus, Web of Science databases, and yielded an initial total of 9016 papers, leaving finally 23 after the screening process. Three sets of meta-analyses estimated the risk of developing psychotic experiences or full clinical psychosis by having experienced maltreatment by an adult or bullying by peers or parental death, using the random-effects model. Bullying by peers (OR = 2.28 [1.64, 4.34]), maltreatment by an adult (OR = 2.20 [1.72, 2.81]) and parental death (OR = 1.24 [1.06, 1.44]) all increased the risk of psychosis. Moderator analysis showed that negative effects of bullying were detected especially in those with genetic liability for psychosis and exposure to multiple trauma types; studies with higher prevalence of males showed a stronger risk for those exposed to parental death. No significant meta-regression was found between the risk of developing a full clinical psychosis or a psychotic experience. Lack of studies hampered the results about the age of trauma occurrence. The cumulative effect of being bullied from peers and experiencing other adversities during childhood and/or adolescence, together with genetic liability for psychosis, appears to confer the highest risk for developing psychotic symptoms later in life.

Characteristics associated with the risk of psychosis among immigrants and their descendants in France

OBJECTIVE

To explore the sociodemographic characteristics that might explain the increased incidence of psychosis among immigrants and their descendants in France.

METHODS

Data were collected for all subjects with first contact for psychosis aged between 18 and 64 years, in two catchment areas in the Paris region. Incidence rates (IR) and incidence rate ratios (IRR) were adjusted for gender and age.

RESULTS

During 805,396 persons-year at risk, we identified 321 cases of first-episode psychosis, of which 129 were immigrants and 78 descendants of immigrants. We found that the geographic origin was associated with the risk of psychosis although generation has little impact. Sub-Saharan African immigrants and their descendants showed the highest risk (IRR = 3.1 and IRR = 2.9, respectively). We observed that living in deprived areas increased the incidence of psychosis (IRR = 1.3, 95CI%: 1.0-1.6), particularly among immigrants (IRR = 1.6; 95% CI: 1.1-2.5). Finally, our study showed that subjects having unstable housing (a proxy for "hard to count population") could inflate the incidence rates among immigrants.

CONCLUSION

The current study shows that the increased risk of psychosis in groups with an immigration background in France is associated with their origin and highlights the importance of socioeconomic factors in modulating this risk.

Urbanicity: The need for new avenues to explore the link between urban living and psychosis

AIM

A growing body of evidence suggests that urban living contributes to the development of psychosis. However, the mechanisms underlying this phenomenon remain unclear. This paper aims to explore the best available knowledge on the matter, identify research gaps and outline future prospects for research strategies.

METHOD

A comprehensive literature survey on the main computerized medical research databases, with a time limit up to August 2017 on the issue of urbanicity and psychosis has been conducted.

RESULTS

The impact of urbanicity may result from a wide range of factors (from urban material features to stressful impact of social life) leading to "urban stress." The latter may link urban upbringing to the development of psychosis through overlapping neuro- and socio-developmental pathways, possibly unified by dopaminergic hyperactivity in mesocorticolimbic system. However, "urban stress" is poorly defined and research based on patients' experience of the urban environment is scarce.

CONCLUSIONS

Despite accumulated data, the majority of studies conducted so far failed to explain how specific factors of urban environment combine in patients' daily life to create protective or disruptive milieus. This undermines the translation of a vast epidemiological knowledge into effective therapeutic and urbanistic developments. New studies on urbanicity should therefore be more interdisciplinary, bridging knowledge from different disciplines (psychiatry, epidemiology, human geography, urbanism, etc.) in order to enrich research methods, ensure the development of effective treatment and preventive strategies as well as create urban environments that will contribute to mental well-being.

Risk of schizophrenia, schizoaffective, and bipolar disorders by migrant status, region of origin, and age-at-migration: a national cohort study of 1.8 million people

BACKGROUND

We assessed whether the risk of various psychotic disorders and non-psychotic bipolar disorder (including mania) varied by migrant status, a region of origin, or age-at-migration, hypothesizing that risk would only be elevated for psychotic disorders.

METHODS

We established a prospective cohort of 1 796 257 Swedish residents born between 1982 and 1996, followed from their 15th birthday, or immigration to Sweden after age 15, until diagnosis, emigration, death, or end of 2011. Cox proportional hazards models were used to model hazard ratios by migration-related factors, adjusted for covariates.

RESULTS

All psychotic disorders were elevated among migrants and their children compared with Swedish-born individuals, including schizophrenia and schizoaffective disorder (adjusted hazard ratio [aHR]migrants: 2.20, 95% CI 1.96-2.47; aHRchildren : 2.00, 95% CI 1.79-2.25), affective psychotic disorders (aHRmigrant1.42, 95% CI 1.25-1.63; aHRchildren: 1.22 95% CI 1.07-1.40), and other non-affective psychotic disorders (aHRmigrant: 1.97, 95% CI 1.81-2.14; aHRchildren: 1.68, 95% CI 1.54-1.83). For all psychotic disorders, risks were generally highest in migrants from Africa (i.e. aHRschizophrenia: 5.24, 95% CI 4.26-6.45) and elevated at most ages-of-migration. By contrast, risk of non-psychotic bipolar disorders was lower for migrants (aHR: 0.58, 95% CI 0.52-0.64) overall, and across all ages-of-migration except infancy (aHR: 1.20; 95% CI 1.01-1.42), while risk for their children was similar to the Swedish-born population (aHR: 1.00, 95% CI 0.93-1.08).

CONCLUSIONS

Increased risk of psychiatric disorders associated with migration and minority status may be specific to psychotic disorders, with exact risk dependent on the region of origin.

Ethnic differences in psychosis-Lay epidemiology explanations

BACKGROUND

Much research attention has been given to the high rates of psychosis diagnosed in the Black community. However, little has been heard about possible reasons for this from Black African and Caribbean mental health service users themselves.

AIMS

To determine how Black African and Caribbean service users perceive and explain these apparent differences.

METHODS

We conducted four focus groups between 2014 and 2015 with 35 participants from the Black African and Black Caribbean community in Lambeth and Southwark, South East London, diagnosed with a psychotic illness. Recruitment was through a local voluntary sector organization and other community contacts.

RESULTS

Each group described an elevated risk of psychosis in their community and explanations followed the following themes, with increased rates due to: (a) an accumulation of stressors due to disadvantaged ethnic minority status, (b) further disadvantage due to inequitable experiences of mental health services, (c) an absence of community support and (d) a double stigma: as a result of external discrimination, due to ethnicity, and internal stigma about mental illness from within the Black community itself.

CONCLUSIONS

Black mental health service users attributed an elevated risk of psychosis in their community to an accumulation of stressors directly related to ethnic minority status.

Predictors of Transition to Psychosis in Individuals at Clinical High Risk

PURPOSE OF REVIEW

Current research is examining predictors of the transition to psychosis in youth who are at clinical high risk based on attenuated psychotic symptoms (APS). Determining predictors of the development of psychosis is important for an improved understanding of mechanisms as well as the development of preventative strategies. The purpose is to review the most recent literature identifying predictors of the transition to psychosis in those who are already assessed as being at risk.

RECENT FINDINGS

Multidomain models, in particular, integrated models of symptoms, social functioning, and cognition variables, achieve better predictive performance than individual factors. There are many methodological issues; however, several solutions have now been described in the literature. For youth who already have APS, predicting who may go on to later develop psychosis is possible. Several studies are underway in large consortiums that may overcome some of the methodological concerns and develop improved means of prediction.

Psychoses sans Frontieres: towards an interdisciplinary understanding of psychosis risk amongst migrants and their descendants

Understanding the excess risk of psychotic disorders in migrant and ethnic minority groups has long been an important research focus in psychiatric epidemiology and public mental health. Heterogeneity between migrant groups based on the region of origin, minority status and other socioeconomic factors may provide clues as to the underlying aetiological mechanisms explaining this risk, as well as informing our general understanding of psychotic disorders. Nonetheless, disentangling the mechanisms underlying this association has been the focus of more speculation and theory to date than empirical research. Now more than ever, we need to move beyond studies which demonstrate excess rates in migrant and ethnic minority groups to novel population-based studies which identify the determinants and mechanisms through which this risk is shaped. In this paper, we review the main hypotheses proposed to explain these disparities and the current level of support for them. We then highlight recent evidence from epidemiology and neuroscience which provides important new clues in our understanding of the aetiology of psychotic disorders. We concluded with suggestions for future interdisciplinary research to prevent this public mental health inequality within a generation.

Non-Genetic Factors in Schizophrenia

PURPOSE OF REVIEW

We review recent developments on risk factors in schizophrenia.

RECENT FINDINGS

The way we think about schizophrenia today is profoundly different from the way this illness was seen in the twentieth century. We now know that the etiology of schizophrenia is multifactorial and reflects an interaction between genetic vulnerability and environmental contributors. Environmental risk factors such as pregnancy and birth complications, childhood trauma, migration, social isolation, urbanicity, and substance abuse, alone and in combination, acting at a number of levels over time, influence the individual's likelihood to develop the disorder. Environmental risk factors together with the identification of a polygenic risk score for schizophrenia, research on gene-environment interaction and environment-environment interaction have hugely increased our knowledge of the disorder.

Amygdala reactivity in ethnic minorities and its relationship to the social environment: an fMRI study

BACKGROUND

Ethnic minority individuals have an increased risk of developing a psychotic disorder, particularly if they live in areas of ethnic segregation, or low own group ethnic density. The neurobiological mechanisms underlying this ethnic minority associated risk are unknown. We used functional MRI to investigate neural responses to faces of different ethnicity, in individuals of black ethnicity, and a control group of white British ethnicity individuals.

METHODS

In total 20 individuals of black ethnicity, and 22 individuals of white British ethnicity underwent a 3T MRI scan while viewing faces of black and white ethnicity. Own group ethnic density was calculated from the 2011 census. Neighbourhood segregation was quantified using the Index of Dissimilarity method.

RESULTS

At the within-group level, both groups showed greater right amygdala activation to outgroup faces. Between groups, the black ethnicity group showed greater right amygdala activation to white faces, compared to the white ethnicity group. Within the black ethnicity group, individuals living in areas of lower own group ethnic density showed greater right amygdala reactivity to white faces (r = -0.61, p = 0.01).

CONCLUSIONS

This is the first time an increased amygdala response to white faces has been demonstrated in individuals of black ethnicity. In the black ethnicity group, correlations were observed between amygdala response and neighbourhood variables associated with increased psychosis risk. These results may have relevance for our understanding of the increased rates of paranoia and psychotic disorders in ethnic minority individuals.

The impact of ethnic density on dispensing of antipsychotic and antidepressant medication among immigrants in the Netherlands

PURPOSE

A higher own-group ethnic density in the area of residence is often associated with a lower risk for psychotic disorder. For common mental disorders the evidence is less convincing. This study explores whether these findings are mirrored in data on dispensing of antipsychotics and antidepressants.

METHODS

Health insurance data on dispensed medication among all adults living in the four largest Dutch cities were linked to demographic data from Statistics Netherlands. Dispensing of antipsychotics and antidepressants in 2013 was analyzed in relation to the proportion of the own ethnic group in the neighborhood.

RESULTS

Higher own-group ethnic density was associated with lower dispensing of antipsychotics among the Moroccan-Dutch (N = 115,455), after adjusting for age, gender, and SES of the neighborhood (OR_adj for the highest vs. the lowest density quintile = 0.72 [0.66-0.79]). However, this association vanished after adjustment for household composition (OR_adj = 0.93 [0.85-1.03]). Similar results were found for the Turkish-Dutch (N = 105,460) (OR_adj = 0.86 [0.76-0.96] and 1.05 [0.94-1.18]). For those of Surinamese (N = 147,123) and Antillean origin (N = 41,430), in contrast, the association between ethnic density and lower risk remained after each adjustment (P < 0.001). For antidepressants, a negative association with own-group ethnic density was consistently found for those of Antillean origin (OR_adj = 0.62 [0.52-0.74]) only.

CONCLUSION

These data on dispensing of psychomedication confirm the ethnic density hypothesis for psychosis alongside earlier equivocal findings for other mental disorders. The negative association between own-group ethnic density and dispensing of antipsychotics among the Moroccan- and Turkish-Dutch may be explained, at least in part, by a favourable household composition (i.e., living in a family) in high-density neighborhoods.

Ethnic density, urbanicity and psychosis risk for migrant groups - A population cohort study

BACKGROUND

Rates of psychotic disorder are raised for many migrant groups. Understanding the role played by the social context in which they live may help explain why. This study investigates the effect of both neighbourhood ethnic density and urbanicity on the incidence of non-affective psychosis for migrant groups.

METHOD

Population based cohort of all those born 1965 or later followed from their 15th birthday (2,224,464 people) to 1st July 2013 (37,335,812 person years). Neighbourhood exposures were measured at age 15.

RESULTS

For all groups incidence of non-affective psychosis was greater in lower ethnic density neighbourhoods. For migrants of African origin there was a 1.94-fold increase (95% CI, 1.17-3.23) comparing lowest and highest density quintiles; with similar effects for migrants from Europe (excluding Scandinavia): incidence rate ratio (IRR) 1.99 (95% CI, 1.56-2.54); Asia: IRR 1.63 (95% CI, 1.02-2.59); and the Middle East: IRR 1.68 (95% CI, 1.19-2.38). This initial analysis found no evidence for an urbanicity effect for migrant groups. Adjusting for ethnic density revealed a positive association between level of urbanicity and psychosis for two groups, with a statistically significant linear trend (average effect of a one quintile increase) for migrants from Europe: IRR 1.09 (95% CI, 1.02-1.16) and the Middle East: IRR 1.12 (95% CI, 1.01-1.23).

CONCLUSIONS

In this first nationwide population-based study of ethnic density, urbanicity and psychosis we show that lower ethnic density is associated with increased incidence of non-affective psychosis for different migrant groups; masking urban/rural differences in psychosis for some groups.

Stress, trauma, and posttraumatic stress disorder in migrants: a comprehensive review

OBJECTIVE

There is growing evidence supporting the association between migration and posttraumatic stress disorder (PTSD). Considering the growing population of migrants and the particularities of providing culturally sensitive mental health care for these persons, clinicians should be kept up to date with the latest information regarding this topic. The objective of this study was to critically review the literature regarding migration, trauma and PTSD, and mental health services.

METHODS

The PubMed, SciELO, LILACS, and ISI Web of Science databases were searched for articles published in Portuguese, English, Spanish, or French, and indexed from inception to 2017. The following keywords were used: migration, mental health, mental health services, stress, posttraumatic stress disorder, and trauma.

RESULTS

Migration is associated with specific stressors, mainly related to the migratory experience and to the necessary process of acculturation occurring in adaptation to the host country. These major stressors have potential consequences in many areas, including mental health. The prevalence of PTSD among migrants is very high (47%), especially among refugees, who experience it at nearly twice the rate of migrant workers.

CONCLUSIONS

Mental health professionals must be trained to recognize and provide appropriate care for posttraumatic and/or stress-related disorders among migrants.

Ethnic Minority Status, Age-at-Immigration and Psychosis Risk in Rural Environments: Evidence From the SEPEA Study

OBJECTIVE

Several ethnic minority groups experience elevated rates of first-episode psychosis (FEP), but most studies have been conducted in urban settings. We investigated whether incidence varied by ethnicity, generation status, and age-at-immigration in a diverse, mixed rural, and urban setting.

METHOD

We identified 687 people, 16-35 years, with an ICD-10 diagnosis of FEP, presenting to Early Intervention Psychosis services in the East of England over 2 million person-years. We used multilevel Poisson regression to examine incidence variation by ethnicity, rural-urban setting, generation status, and age-at-immigration, adjusting for several confounders including age, sex, socioeconomic status, population density, and deprivation.

RESULTS

People of black African (incidence rate ratio: 4.06; 95% confidence interval [CI]: 2.63-6.25), black Caribbean (4.63; 95% CI: 2.38-8.98) and Pakistani (2.31; 95% CI: 1.35-3.94) origins were at greatest FEP risk relative to the white British population, after multivariable adjustment. Non-British white migrants were not at increased FEP risk (1.00; 95% CI: 0.77-1.32). These patterns were independently present in rural and urban settings. For first-generation migrants, migration during childhood conferred greatest risk of psychotic disorders (2.20; 95% CI: 1.33-3.62).

CONCLUSIONS

Elevated psychosis risk in several visible minority groups could not be explained by differences in postmigratory socioeconomic disadvantage. These patterns were observed across rural and urban areas of our catchment, suggesting that elevated psychosis risk for some ethnic minority groups is not a result of selection processes influencing rural-urban living. Timing of exposure to migration during childhood, an important social and neurodevelopmental window, may also elevate risk.

Mood disorders in first- and second-generation immigrants: systematic review and meta-analysis

BackgroundAlthough there are consistent reports of higher psychosis rates among immigrants, the information on mood disorders is limited.AimsTo review and quantify the difference in incidence of mood disorders in first- and second-generation immigrant (FGI and SGI) groups v. non-immigrants.MethodPubMed, EMBASE and PsycINFO were searched for articles from cohort studies reporting incidence of mood disorders among FGIs and SGIs.ResultsEighteen studies met our inclusion criteria. The summary relative risk (RR) for FGIs was 1.25 (95% CI 1.11-1.41), based on 17 effect sizes and 6120 cases, and 1.16 (95% CI 0.96-1.40) for SGIs based on three effect sizes. Men seemed at higher risk (RR = 1.29, 95% CI 1.06-1.56).ConclusionsClinicians should view FGIs as a group at risk of mood disorders, especially men. Further research is needed to understand immigrants' risk, especially in SGI.

Social adversities and psychotic symptoms: A test of predictions derived from the social defeat hypothesis

Based on the social defeat (SD) hypothesis, this study examines the postulate that various social adversities converge into one common factor, and whether this factor has an effect on psychotic symptoms while controlling for its effect on depression and anxiety. Competing hypotheses arguing for the reverse effect were also tested. The study was a cross-sectional survey in a community sample (N =2350) from Germany (n=786), Indonesia (n=844), and the United States (n=720). Confirmatory factor analysis (CFA) and path analysis with structural equation modeling were used to test the hypotheses. In the CFA two factors reflecting current and past experiences of SD could be identified with acceptable fit. Path analysis indicated acceptable fit for both SD and reverse models, and both the path from current SD to psychotic symptoms and the reverse one were significant, although the former was stronger than the latter. Interestingly, the current but not the past SD factor was significantly associated with psychotic symptoms. Overall, the results indicate that postulates derived from the SD hypothesis fit the data. However, longitudinal research is needed to further confirm the postulated directionality of the associations.

Rethinking Schizophrenia in the Context of the Person and Their Circumstances: Seven Reasons

We know a great deal about schizophrenia, but the current state of the art is one of uncertainty. Researchers are confused, and patients feel misunderstood. This situation has been identified as due largely to the fact that the dominant neurobiological perspective leaves out the person. The aim of the present article is to review and integrate a series of clinical, phenomenological, historical, cultural, epidemiological, developmental, epigenetic, and therapeutic phenomena in support of a suggestion that schizophrenia is above all a disorder of the person rather than of the brain. Specifically, we review seven phenomena, beginning with the conception of schizophrenia as a particular disorder of the self. We continue by looking at its recent origin, as a modern phenomenon, its juvenile onset, related to the formation of the self, the better prognosis in developing countries compared to developed countries, and the high incidence of the disorder among migrants. In the context of these phenomena of a marked socio-cultural nature, we consider the so-called "genetic myth," according to which schizophrenia would have a genetic origin. On reviewing the current genetic emphasis in the light of epigenetics, it emerges that the environment and behavior recover their prominent role in the vicissitudes of development. The seventh reason, which closes the circle of the argument, concerns the role of interpersonal "chemistry" in recovery of the sense of self.

Refugee migration and risk of schizophrenia and other non-affective psychoses: cohort study of 1.3 million people in Sweden

OBJECTIVE

To determine whether refugees are at elevated risk of schizophrenia and other non-affective psychotic disorders, relative to non-refugee migrants from similar regions of origin and the Swedish-born population.

DESIGN

Cohort study of people living in Sweden, born after 1 January 1984 and followed from their 14th birthday or arrival in Sweden, if later, until diagnosis of a non-affective psychotic disorder, emigration, death, or 31 December 2011.

SETTING

Linked Swedish national register data.

PARTICIPANTS

1,347,790 people, including people born in Sweden to two Swedish-born parents (1,191,004; 88.4%), refugees (24,123; 1.8%), and non-refugee migrants (132,663; 9.8%) from four major refugee generating regions: the Middle East and north Africa, sub-Saharan Africa, Asia, and Eastern Europe and Russia.

MAIN OUTCOME MEASURES

Cox regression analysis was used to estimate adjusted hazard ratios for non-affective psychotic disorders by refugee status and region of origin, controlling for age at risk, sex, disposable income, and population density.

RESULTS

3704 cases of non-affective psychotic disorder were identified during 8.9 million person years of follow-up. The crude incidence rate was 38.5 (95% confidence interval 37.2 to 39.9) per 100,000 person years in the Swedish-born population, 80.4 (72.7 to 88.9) per 100,000 person years in non-refugee migrants, and 126.4 (103.1 to 154.8) per 100,000 person years in refugees. Refugees were at increased risk of psychosis compared with both the Swedish-born population (adjusted hazard ratio 2.9, 95% confidence interval 2.3 to 3.6) and non-refugee migrants (1.7, 1.3 to 2.1) after adjustment for confounders. The increased rate in refugees compared with non-refugee migrants was more pronounced in men (likelihood ratio test for interaction χ(2) (df=2) z=13.5; P=0.001) and was present for refugees from all regions except sub-Saharan Africa. Both refugees and non-refugee migrants from sub-Saharan Africa had similarly high rates relative to the Swedish-born population.

CONCLUSIONS

Refugees face an increased risk of schizophrenia and other non-affective psychotic disorders compared with non-refugee migrants from similar regions of origin and the native-born Swedish population. Clinicians and health service planners in refugee receiving countries should be aware of a raised risk of psychosis in addition to other mental and physical health inequalities experienced by refugees.

Schizophrenia and other psychotic disorders in Caribbean-born migrants and their descendants in England: systematic review and meta-analysis of incidence rates, 1950-2013

PURPOSE

Increased risk of schizophrenia and other psychotic disorders among black Caribbean migrants and their descendants have been described since the 1960s. It remains unclear whether this risk varies over time, between rural and urban areas, or according to methodological artefact.

METHODS

We conducted a systematic review of the incidence of adult-onset psychotic disorders in black Caribbean groups relative to the baseline population in England, published 1950-2013. Subject to sufficient data (N ≥ 5) we used random effects meta-analyses to estimate pooled incidence rates (IR) and rate ratios (IRR) of seven psychotic disorder outcomes, and meta-regression to inspect whether any variation was attributable to study-level methodological features, including case ascertainment, denominator reliability, choice of baseline population and study quality.

RESULTS

Eighteen studies met inclusion for review. Sixteen demonstrated statistically significant elevated incidence rates in the black Caribbean group, present across all major psychotic disorders, including schizophrenia and bipolar disorder. Methodological quality increased over time (p = 0.01), but was not associated with estimated IR or IRR. For schizophrenia (N = 11 studies) the pooled IRR in the black Caribbean group was 4.7 (95 % CI 3.9-5.7) relative to the baseline; no evidence of publication bias was observed. We found weak evidence to suggest schizophrenia IRRs were smaller from studies in more urban settings (odds ratio 0.98; 95 % CI 0.96-1.00; p = 0.06).

CONCLUSIONS

Higher incidence rates of psychotic disorders have been present for more than 60 years amongst black Caribbean ethnic groups in England, despite improved study methodologies over time. Aetiological explanations appear to more parsimoniously account for this excess than methodological biases.