People are now moving faster and further and in larger numbers than ever before. One million people emigrate permanently, and over a million more seek asylum each year.¹ In the twelve-month period up to April 2000, some 24,000 non-Irish immigrants took up residence in Ireland.²

Migration affects health. Immigrants have higher rates of cardiovascular disease, colorectal carcinoma and melanoma than non-immigrant populations.³ In the United States, immigrants have higher mortality from stomach cancer, brain cancer and infectious disease.⁴ In the United Kingdom, children with ethnic origin in south Asia have higher rates of leukaemia, lymphoid carcinoma, lymphoma and hepatic tumours.⁵ In Israel, cardiac disease in immigrants is markedly more severe than in the native population.⁶ Clinical manifestations of physical disease, such as tuberculosis, are also significantly altered in immigrant populations.

Migration also affects mental health. In the United Kingdom, Irish, Caribbean and Pakastani men have higher rates of suicidal thoughts and deliberate self-harm.⁷ In Oslo, post-traumatic stress disorder affects 46.6% of refugees.⁸ Egyptian and Asian immigrants have higher rates of bulimia and anorexia nervosa.⁹

However, it is the relationship between migration and schizophrenia that is most baffling. Schizophrenia is six times more common in African-Carribeans living in the United Kingdom, compared to the native population¹⁰ and four times more common among migrants to the Netherlands compared to the native population.¹¹ There is no data available for migrant populations in Ireland.

Schizophrenia occurs more commonly in the relatives of patients with schizophrenia. This increased risk is no greater in the first generation relatives of African-Caribbean patients than it is in the general population. The increased risk is much greater, however, in second generation relatives of African-Caribbean patients.¹² This is consistent with the existence of an environmental factor which may act synergistically with genetic predisposition to produce schizophrenia in this group.

There are several possible reasons for the increased risk of schizophrenia in migrants. It was initially assumed that schizophrenia occurred more commonly in the country of origin of immigrants⁹, but epidemiological data do not support this view.^13,14 There is no convincing evidence of increased rates of biological risk factors in immigrants countries of origin.⁹ Obstetric complications are a risk factor for schizophrenia. It had been presumed that African-Carribean women had more obstetric complications than the general population, thus accounting for the increased rate of schizophrenia in this group. African-Carribean women actually have a decreased rate of obstetric complications compared to indigenous English women.¹² The increased susceptibility of immigrant women to rubella virus infection has prompted studies of viral aetiology, but no convincing model has emerged.^10,15

Odegaard suggested that people with mental illness were more likely than other people to migrate, thus leading to an increased prevalence of illness in migrant groups.¹⁶ This theory of selective migration is unconvincing, however, given the amount of planning and paperwork involved in the process of migration. A person with schizophrenia would be less, rather than more, likely to complete this. In addition, migrants form a heterogenous group which migrates for a variety of reasons as diverse as war, poverty, political oppression and the search for work or education. In light of this diversity of reasons for migration it is unlikely that the presence or absence of schizophrenia acts as a critical factor in precipitating migration.

Adverse social circumstances are strongly associated with the development of schizophrenia following migration.¹⁷ This may be related to unidentified environmental factors associated with city living, social isolation, overcrowding or unemployment. It is likely that migrant populations will be exposed to this environment in a more extreme form. Members of the African-Caribbean population in England are more likely to live in single parent families, not to know their own parents, to have low educational attainment and to have been imprisoned.¹⁷ However, similarly socially deprived groups in other countries have no increased rate of schizophrenia. Bhugra et al showed that 80% of African immigrants with first episode schizophrenia were unemployed, as compared to 40% of whites and Asians.¹⁸ Community structure has a decisive effect on health and the lack of social cohesion amongst migrants is well described in migrant groups known to have increased rates of schizophrenia.^{19, 20}

Cultural factors can exert a significant influence on psychopathology. Some say that migrants are more commonly diagnosed with schizophrenia because of a lack of cultural awareness among clinicians or racism on the part of psychiatrists. However, Lewis et al sent a series of case vignettes to a selection of British psychiatrists describing symptoms in patients from a variety of ethnic groups and found that psychiatrists were actually less likely to diagnose schizophrenia in African-Caribbean patients.²¹ The relationship between racial attitudes in medical practitioners and mental illness in migrants is a complex one. The expression of psychiatric symptoms varies significantly between cultural groups, but misdiagnosis alone cannot account for high rates of schizophrenia amongst immigrants.⁹

Institutional racism was also thought to account for the marked differences in the pathways to psychiatric care in migrant and non-migrant populations. The pathway to care for migrants is characterized by a high rate of involuntary admission and increased involvement of police, as opposed to general practitioners.²² Burnett et al suggest that migrants lack of involvement at the primary care level leads to a concomitant rise in involuntary admissions.²³ There is a strong need for service developments that specifically address the mental health needs of migrants. However, the development of segregated services, with ethnic matching of service provider and user, constitute an inappropriate model for future development.²⁴ These practices maintain racism and fail to acknowledge that the risk of schizophrenia varies considerably between migrant groups.²⁵

Immigration presents particular challenges in Ireland, a country more accustomed to the outward rather than inward flow of migrants.¹ We need to collect epidemiological data that detail the number of migrants currently resident in Ireland and medical data about the illnesses they develop. This information is essential for rational service planning. It will also help us learn more about the illnesses themselves and ultimately enhance the quality of mental health care provided to all.

BE Gavin, BD Kelly, A Lane, E O'Callaghan

Stanley Research Foundation,
Cluain Mhuire Family Centre,
Newtownpark Avenue,
Blackrock,
Co Dublin, Ireland
Tel: + 353 1 217 2100
Fax: + 353 1 283 3886

References

1. Murphy JFA. Migrants Right to Health. Irish Medical Journal 2001; 94: 164
2. Central Statistics Office. Population and Migration Estimates, April 2000. Available at www.cso.ie (verified 14th May 2001)