Skip to main content
×
×
Home

Information:

  • Access
  • Open access

Figures:

Actions:

      • Send article to Kindle

        To send this article to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about sending to your Kindle. Find out more about sending to your Kindle.

        Note you can select to send to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

        Find out more about the Kindle Personal Document Service.

        Origin and schizophrenia in young refugees and inter-country adoptees from Latin America and East Africa in Sweden: a comparative study
        Available formats
        ×
        Send article to Dropbox

        To send this article to your Dropbox account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Dropbox.

        Origin and schizophrenia in young refugees and inter-country adoptees from Latin America and East Africa in Sweden: a comparative study
        Available formats
        ×
        Send article to Google Drive

        To send this article to your Google Drive account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Google Drive.

        Origin and schizophrenia in young refugees and inter-country adoptees from Latin America and East Africa in Sweden: a comparative study
        Available formats
        ×
Export citation

Abstract

Background

Migrants' socioeconomic adversity has been linked to schizophrenia.

Aims

To investigate whether the more favourable socioeconomic situation of adoptees prevents them from the high risk of schizophrenia found in other migrants.

Method

Register study in a cohort of refugees and inter-country adoptees aged 16–40 years, born in East Africa (n=8389), Latin America (n=11 572) and 1.2 million native Swedes. Cox-regression models estimated hazard ratios (HRs) of schizophrenia in data from psychiatric care.

Results

Despite diverse income levels, HRs for schizophrenia were similar for refugees and adoptees, with East Africans having the highest HRs: 5.83 (3.30–10.27) and 5.80 (5.03–6.70), followed by Latin Americans: HRs 3.09 (2.49–3.83) and 2.31 (1.79–2.97), compared with native Swedes. Adjustment for income decreased these risks slightly for refugees, but not for adoptees.

Conclusions

This study suggests that risk factors associated with origin are more important determinants of schizophrenia than socioeconomic adversity in the country of settlement.

Footnotes

Declaration of interest

None.

Epidemiological studies conducted in Europe and Israel have consistently shown an increased risk for schizophrenia and other psychotic disorders in migrants, especially among visible minorities. 15 The aetiology behind this increased morbidity has caused considerable debate.

The explanations proposed can roughly be divided into risk factors associated with the country of origin, such as a higher incidence in the populations of origin, perinatal risk factors and malnutrition; 1,3 stressors related to the migration process itself and its underlying social and environmental aftermath; 2,4 and finally risk factors in the country of resettlement, such as experience of discrimination and racism, socioeconomic adversity and housing in low-status neighbourhoods. 610

Immigration to Sweden of children under the age of 18 years from the 1970s onwards has been dominated by refugees and inter-country adoptees. Sweden has the largest population of inter-country adoptees in Europe and the highest per capita population of inter-country adoptees in the world. 11 Refugees and inter-country adoptees can both be expected to have experienced adversity in the country of origin, and they also share the experience after migration of having a physical appearance that differs from that of the majority population. In terms of socioeconomic living conditions after migration, however, there are large differences, with the adoptees being raised by parents from the majority population, often with considerable material and educational resources, whereas refugees on average have a much lower socioeconomic position. 12,13

In this national cohort study, we compared the rates of schizophrenia in these two diverse types of migrants, refugees and adoptees, with origin in two different regions in the world, Latin America and East Africa, and compare them with the native Swedish population. Our aim thus was to exploit this natural experiment to investigate whether the more affluent socioeconomic situation of adoptees after migration protects them from the higher risk for schizophrenia associated with migration and if these factors are more important than risk factors associated with the population of origin.

Method

Sweden has a long tradition of national registers with high-quality data for health and socioeconomic indicators, protected by special legislation. 14 These registers can be linked to each other through individually unique 10-digit personal identification number (PIN) that follows every Swedish resident from birth (or time of immigration) to death. The study was approved by the Regional Ethics Committee in Stockholm before any records were linked.

Study population

The study population includes all individuals born between 1972 and 1988 who were alive and resident in Sweden in the Register of the Total Population (RTP) on 31 December 2004. The migrant population was created from the two largest migrant populations in Sweden in these cohorts that include significant numbers of adoptees as well as refugees, Latin Americans and East Africans. We first identified 7956 individuals from East Africa (Somalia, Eritrea and Ethiopia) and 5824 individuals from Latin America who were under the age of 19 years when they received a permanent residency in Sweden as refugees or because of family relations to a refugee, according to STATIV – a longitudinal database for integration studies. Inter-country adoptees were identified in the Multi-Generation register; we identified 433 individuals from East Africa and 5748 from Latin America who were under the age of 8 years when they settled in Sweden, as this is the most common age profile among the adopted children in Sweden. Information on the country of birth, date of immigration and year of birth was obtained from the RTP. A total of 1 255 782 native Swedish born with two Swedish-born parents constituted the comparison population.

Predictors

Information on the region of birth and age at immigration was obtained from the RTP. We categorised into East Africa and Latin America. The migrant population was categorised into refugee if they had obtained residency as a refugee or family relation to a refugee according to STATIV and inter-country adoptees if they were adopted under the age of 8 years and had at least one Swedish-born adoptive parent according to the Multi-Generation register.

Outcome

The outcome was defined as at least one entry of specialised psychiatric in-patient or out-patient care, with a diagnosis of schizophrenia, F20-F29 (according to ICD-10). We included the first case of schizophrenia from 1 January 2005 to 31 December 2012 in the Swedish Patient Register held by the Swedish National Board of Health and Welfare. The quality of the schizophrenia diagnosis in the Swedish Patient Register has been evaluated and found to be acceptable. 15

Covariates

Sociodemographic variables, age, gender, disposable income and type of municipality, were retrieved from the Longitudinal Integration Database for Health Insurance and Labor Market Studies (LISA) in 2004. Since the Swedish health organisation has been shown to have regional differences in provision of care between rural and urban communities, we created an indicator of type of municipality, defined by the municipality of residence in 2004 into three categories: ‘big city’ (metropolitan areas of Sweden's three largest cities Stockholm, Gothenburg and Malmo); town (other predominately urban communities) and rural. This categorisation is recommended by the Swedish Association of Local Authorities and Regions. Disposable income included all registered sources of income deducted by taxes and thereafter divided by consumer units in the household according to a formula developed by Statistics Sweden. The variable was divided into quintiles in the analysis.

Statistical analysis

Cox-regression models estimated hazard ratios (HRs) of schizophrenia in person time in the study from January 2005 to December 2012. Person time was calculated as time from start of the follow-up to the first hospital admission or out-patient visit with a diagnosis of schizophrenia, death, emigration or end of the study, whichever was sooner.

In Model 1 we adjusted for gender, age and type of municipality of residence. Disposable income was adjusted for in Model 2. First, we analysed the HRs of schizophrenia among refugees and inter-country adoptees from Latin America and East Africa with the general Swedish population as the reference category. Thereafter, we analysed differences in the HRs of schizophrenia between Latin Americans and East Africans in each migrant category separately, using the same adjustment procedure.

A sensitivity analysis on the significance of age at immigration on the outcome in the refugees and inter-country adoptees was conducted, where the adopted group was categorised into 0–1, 2–3 and 4–7 years of age and the refugee group into categories 0–6, 7–12 and 13–19 years of age.

Results

Sociodemographic characteristics of the study population are presented in Table 1. The study population consisted of slightly more males than females, with the exception of inter-country adoptees from East Africa. The migrant study groups were younger than the Swedish comparison population with refugees having the lowest age (mean age 23 years). Inter-country adoptees arrived in Sweden in early childhood (mean age 1 year), in contrast to the refugees (mean ages 13 and 10 years respectively). The refugee study groups were most likely to live in the metropolitan areas of Sweden's three largest cities: Stockholm, Gothenburg and Malmo. The lowest income (quintile) was found among the refugee study groups. No considerable income differences were found between native Swedish and inter-country adoptees.

Table 1 Sociodemographic indicators of the study population

Sweden East Africa Latin America
Variables Variable characteristics Native Swedish n=11 572 % Adoptees n=11 572 % Refugees n=11 572 % Adoptees n=11 572 % Refugees n=11 572 %
Gender Male 51.4 45.2 55.9 55.3 53.2
Female 48.6 54.8 44.1 47.7 47.8
Age in 2005 Mean age 28.9 26.7 22.9 23.2 23.1
Age at immigration Mean age 1.3 12.7 1.5 10.5
Municipality Big city 42.7 53.1 72.1 51.6 65.9
Town 43.7 37.5 25.6 40.8 29.3
Rural 13.6 9.4 2.3 7.6 4.8
Income in quintiles 1 16.0 12.6 58.0 15.3 38.3
2 19.8 18.9 18.7 18.8 26.2
3 20.7 18.7 9.4 20.6 18.0
4 21.8 23.6 8.5 24.1 11.7
5 21.7 26.2 5.4 21.3 5.8

a N=population size.

The rates of hospital admission and/or out-patient care because of schizophrenia were 3.2% and 2.6% respectively, among adoptees and refugees born in East Africa and 1.5 and 1.1% in adoptees and refugees from Latin America, in comparison with 0.5% in the native Swedes. When adjusted for age, gender and type of municipality, the HRs of schizophrenia were higher for East African inter-country adoptees 5.83 (3.30–10.27) and refugees 5.80 (5.03–6.70) respectively, as well as for Latin American inter-country adoptees, 3.09 (2.49–3.83) and refugees, 2.31 (1.79–2.97). These risks were attenuated somewhat in the refugee population when income was adjusted, whereas the risk estimates for adoptees remained more or less the same after these adjustments (Table 2).

Table 2 Rates of hospital care because of schizophrenia among inter-country adoptees and refugees in Sweden

Type of care Cox regression models
Outpatient care Inpatient care Any type of care HR 95% CI HR 95% CI
Region of birth N a (%) (%) (%) Model 1 b Model 2 c
Sweden 1255782 5396 (0.4) 3873 (0.3) 6237 (0.5) 1 1
East Africa
   Adoptees 433 13 (3.0) 10 (2.3) 14 (3.2) 5.83 (3.30–10.27) 5.74 (3.26–10.13)
   Refugees 7956 182 (2.3) 157 (2.0) 207 (2.6) 5.80 (5.03–6.70) 4.34 (3.74–5.04)
Latin America
   Adoptees 5748 81 (1.4) 51 (0.9) 87 (1.5) 3.09 (2.49–3.83) 3.11 (2.50–3.85)
   Refugees 5824 56 (1.0) 39 (0.7) 63 (1.1) 2.31 (1.79–2.97) 1.84 (1.43–2.37)

HR, hazard ratio; CI, confidence intervals.

a N=population size.

b Adjusted for age, gender and municipality.

c Adjusted for age, gender, municipality and income.

Sensitivity analyses (not shown in the table) revealed that East African inter-country adoptees had a higher HR for schizophrenia than the Latin American inter-country adoptees: 2.13 (1.16–3.94) as did East African refugees compared with refugees born in Latin America 2.51 (1.87–3.36). In another sensitivity analysis it was shown that inter-country adoptees who arrived at the age of 4 years onwards had a higher risk of schizophrenia than those were arrived at the age 0–1 year: HR 2.33 (1.42–3.82).

Discussion

In this register, follow-up study of schizophrenia in a national cohort of young refugees and international adoptees, a twofold to fivefold higher risk for schizophrenia in the migrant study groups was found in comparison with the native Swedish population. Migrants from East Africa had a higher risk than those from Latin America, irrespective if they were adopted or refugees. Adjusting for income attenuated the higher risk compared with the native population somewhat for the refugee study groups, but not at all for the adoptees. A higher age at arrival was associated with an increased risk for schizophrenia in inter-country adoptees, but not in refugees.

Our results do not support the hypothesis that socioeconomic adversity after settlement is the main explanation behind the increased rates of schizophrenia in migrants in Europe, 6,7 considering the high risk in adoptees despite a favourable income level. Although the limited data available in this register cannot exclude the possibility that the similar pattern in migrants and adoptees from the same origin are caused by altogether different mechanisms, the pattern is more congruent with hypotheses associated with the origin of these migrants.

Risk factors associated with the country of origin can be divided into those that are at play before and after migration. Adoptees and refugees to a certain extent can be expected to share experiences of early life adversity in relation to the economic development of the society where they are born. This includes exposure to such risk factors such as infectious agents, malnutrition and perinatal complications. 16 Latin America consists of middle-income countries, whereas East Africa is much poorer, which would be consistent with their higher risk. Genetic contribution of consanguineous marriages for the overall heritable effects in the aetiology of schizophrenia 17 could to a certain extent also be similar among refugees and adoptees from East Africa. Both refugees and adoptees may have experienced war trauma/maltreatment in the country of origin, and for the adoptees, also early parental separation is mandatory. 18

With regard to risk factors after migration, our findings are congruent with hypotheses about racial discrimination and schizophrenia, since geographic origin is related to physical appearance/colour of the skin in a similar manner in adoptees and refugees. Perceived racial discrimination has been suggested to increase the risk of schizophrenia through chronic stress, feelings of exclusion and hopelessness, low self-esteem and anxiety. These risk factors would be more common in East African migrants, since their physical appearance differs more from the native Swedish population than that of Latin American migrants. Findings linking discrimination and schizophrenia have been reported in Black and ethnic minorities in many European countries. 810,1923 The possibility of discriminatory treatment within the healthcare organisation, through referral bias and differential treatment, also has to be considered as a possibility to explain our findings. Studies in the UK have shown that the excessive risks of schizophrenic diagnosis among visible minorities could be attributed to incorrect schizophrenic diagnosis caused by existence of structural racisms that is embedded within social institutions, policies, etc. 24

The effect of vitamin D deficiency developed in the Swedish sun-deprived environment 25 could also be added to the list of potential risk factors in the country of resettlement that would also apply to refugees and adoptees after migration.

In our study, older age at the time of immigration was associated with increased risks for schizophrenia among adoptees but not for refugees. This is not surprising as previous studies of adoption have demonstrated that older age at adoption is associated with an increased risk for psychiatric morbidity and social maladjustment in general. 26 Older age at migration for them is the same as an older age at adoption, and thus associated with a longer period of exposure to early life deprivation, often in orphanages. 27 In this study, we could not confirm the pattern found in other studies that younger age at immigration is associated with increased risks for psychotic disorder among non-adopted migrants. 28

Strengths and limitations and methodological issues

The major strength of our study is the exploitation of a uniquely large population of international adoptees in Sweden, which enabled us to compare risks in migrant populations in very diverse socioeconomic contexts, but with a similar origin. The high quality of the Swedish registers used also provides a very low rate of attrition, which is otherwise a main problem in studies of mental health in migrants. 15

The study also has some noteworthy shortcomings that need to be considered when interpreting our results. The population from Latin America is quite diverse in terms of geographic origin with most adoptees originating in Colombia and most refugees from Chile. In the East African population, most adoptees arrived from Ethiopia, whereas refugees arrived from Somalia. Furthermore, despite the uniquely large population of international adoptees in Sweden, the population of adoptees that could be compared with refugees from similar origins was too small to allow for a more sophisticated analysis of pre- and post-migration risk factors. Thus, further studies are needed to investigate these associations, especially among individuals born in East Africa that have a very high risk of schizophrenia in Sweden. It is also important to highlight that the crude nature of our exposure does not allow us to test more specific mechanisms about possible mediating pathways underlying the associations, for instance, the role of urbanicity, misuse of substances, genetic indicators, discrimination, vitamin D, etc.

In conclusion, this study found that adoptees, despite having a more favourable level of income, had similar increased rates of schizophrenia compared with refugees with the same origin in East Africa or Latin America. East Africans had the highest risks, with a fivefold to sixfold increase compared with the native population. Further studies are needed to clarify the mechanisms behind this pattern.

References

1 Howes, OD, McDonald, C, Cannon, M, Arseneault, L, Boydell, J, Murray, RM. Pathways to schizophrenia: the impact of environmental factors. Int J Neuropsychopharmacol 2004; 7 (suppl 1): S713.
2 Cantor-Graae, E, Pedersen, CB, McNeil, TF, Mortensen, PB. Migration as a risk factor for schizophrenia: a Danish population-based cohort study. Br J Psychiatry 2003; 182: 117–22.
3 Brown, AS. The environment and susceptibility to schizophrenia. Prog Neurobiol 2011; 93: 2358.
4 Bhugra, D. Migration and schizophrenia. Acta Psychiatr Scand 2000; 102: 6873.
5 Weiser, M, Werbeloff, N, Vishna, T, Yoffe, R, Lubin, G, Shmushkevitch, M, et al. Elaboration on immigration and risk for schizophrenia. Psychol Med 2008; 38: 1113–9.
6 Veling, W, Susser, E. Migration and psychotic disorders. Expert Rev Neurother 2011; 11: 7586.
7 Hjern, A, Wicks, S, Dalman, C. Social adversity contributes to high morbidity in psychoses in immigrants: a national cohort study in two generations of Swedish residents. Psychol Med 2004; 34: 1025–33.
8 Veling, W, Selten, J-P, Mackenbach, JP, Hoek, HW. Symptoms at first contact for psychotic disorder: comparison between native Dutch and ethnic minorities. Schizophr Res 2007; 95: 30–8.
9 Berg, AO, Melle, I, Rossberg, JI, Romm, KL, Larsson, S, Lagerberg, TV, et al. Perceived discrimination is associated with severity of positive and depression/anxiety symptoms in immigrants with psychosis: a cross-sectional study. BMC Psychiatry 2011; 11: 77.
10 Anderson, KK, Cheng, J, Susser, E, McKenzie, KJ, Kurdyak, P. Incidence of psychotic disorders among first-generation immigrants and refugees in Ontario. Can Med Assoc J 2015; 178: E2279286.
11 Selman, P. Intercountry adoption in the new millennium; the “quiet migration” revisited. Popul Res Policy Rev 2002; 21: 205–25.
12 Cantor-Graae, E, Selten, J-P. Schizophrenia and migration: a meta-analysis and review. Am J Psychiatry 2005; 162: 1224.
13 Hjern, A, Wicks, S, Dalman, C. Social adversity contributes to high morbidity in psychoses in immigrants–a national cohort study in two generations of Swedish residents. South Asia 2004; 1: 176.
14 Rosén, M. National health data registers: a Nordic heritage to public health. Scand J Public Health 2002; 30: 81–5.
15 Dalman, C, Broms, J, Cullberg, J, Allebeck, P. Young cases of schizophrenia identified in a national inpatient register. Soc Psychiatry Psychiatr Epidemiol 2002; 37: 527–31.
16 Sharpley, MS, Hutchinson, G, Murray, RM, McKenzie, K. Understanding the excess of psychosis among the African–Caribbean population in England review of current hypotheses. Br J Psychiatry 2001; 178 (suppl 40): s608.
17 Bittles, A, Black, M. Consanguinity, human evolution, and complex diseases. Proc Natl Acad Sci USA 2010; 107: 1779–86.
18 Morgan, C, Kirkbride, J, Leff, J, Craig, T, Hutchinson, G, McKenzie, K, et al. Parental separation, loss and psychosis in different ethnic groups: a case-control study. Psychol Med 2007; 37: 495503.
19 Karlsen, S, Nazroo, JY, McKenzie, K, Bhui, K, Weich, S. Racism, psychosis and common mental disorder among ethnic minority groups in England. Psychol Med 2005; 35: 1795–803.
20 Cooper, C, Morgan, C, Byrne, M, Dazzan, P, Morgan, K, Hutchinson, G, et al. Perceptions of disadvantage, ethnicity and psychosis. Br J Psychiatry 2008; 192: 185–90.
21 Fearon, P, Kirkbride, JB, Morgan, C, Dazzan, P, Morgan, K, Lloyd, T, et al. Incidence of schizophrenia and other psychoses in ethnic minority groups: results from the MRC AESOP study. Psychol Med 2006; 36: 1541–50.
22 Veling, W, Selten, J-P, Susser, E, Laan, W, Mackenbach, JP, Hoek, HW. Discrimination and the incidence of psychotic disorders among ethnic minorities in the Netherlands. Int J Epidemiol 2007; 36: 761–8.
23 Selten, J-P, Cantor-Graae, E. Social defeat: risk factor for schizophrenia? Br J Psychiatry 2005; 187: 101–2.
24 Cope, R. The compulsory detention of Afro-Caribbeans under the mental health act. J Ethnic Migrat Stud 1989; 15: 343–56.
25 Dealberto, M. Why are immigrants at increased risk for psychosis? Vitamin D insufficiency, epigenetic mechanisms, or both? Med Hypotheses 2007; 68: 259–67.
26 Hjern, A, Lindblad, F, Vinnerljung, B. Suicide, psychiatric illness, and social maladjustment in intercountry adoptees in Sweden: a cohort study. Lancet 2002; 360: 443–8.
27 O'connor, TG, Rutter, M, English, Team RAS Attachment disorder behavior following early severe deprivation: extension and longitudinal follow-up. J Am Acad Child Adolesc Psychiatry 2000; 39: 703–12.
28 Veling, W, Hoek, HW, Selten, J-P, Susser, E. Age at migration and future risk of psychotic disorders among immigrants in the Netherlands: a 7-year incidence study. Am J Psychiatry 2011; 168: 1278–85.