Elizabeth Cantor-Graae

A growing number of population-based studies^1-5 have found increased incidence rates of nonaffective and affective psychoses in first- and second-generation immigrants, firmly establishing a link between foreign migration and higher risk for the development of schizophrenia and other psychotic disorders. The mechanisms underlying this association remain unclear, although potential explanations encompass a broad range of factors, including selective migration of predisposed individuals and exposure to risk factors, such as cannabis use, perinatal complications, low levels of vitamin D, childhood trauma, and urban upbringing.^1,6,7 To date, none of the potential explanations have been confirmed or ruled out. Aspects of social stress have been increasingly highlighted in recent years because of the especially high rates of schizophrenia found in immigrants having dark skin^1,2,8 or marked differences in culture and appearance compared with the host culture.^9,10 The increased risk for psychotic disorders found in second-generation immigrants suggests that postmigration aspects of the social context (eg, socioeconomic deprivation or long-term experiences of social defeat) may be more important risk mediators than the migration process itself.^6,11 Although early data emphasized generational differences, with higher rates of psychotic disorders found in second-generation immigrants compared with first-generation immigrants,¹ a recent meta-analysis⁴ showed no overall generational differences but found considerable consistency in increased risk for psychotic disorders across a diversity of immigrant or racial/ethnic minority groups, with the greatest risks for such disorders in migrants from countries where the predominant skin color is black. Although other factors cannot be ruled out, converging evidence suggests that adverse aspects of the social environment may be important contributors to the development of psychotic disorders in immigrants.

In Uganda, a previous study reported high HIV prevalence in persons with severe mental illness (SMI) compared to the general population, suggesting that persons with SMI might constitute a high-risk group for HIV. However, the study included first-time psychiatric admissions only, a group whose HIV prevalence may not reflect the prevalence in persons with SMI in general. We determined prevalence and correlates of HIV in both first-time and previous psychiatric admissions, in a psychiatric hospital in Uganda.

Poor mental health predicts sexual risk behaviours in high-income countries, but little is known about this association in low-income settings in sub-Saharan Africa where HIV is prevalent. This study investigated whether depression, psychological distress and alcohol use are associated with sexual risk behaviours in young Ugandan adults.

Background:  Increasing numbers of intercountry adoptees are reaching adulthood, the age of onset for most serious mental disorders. Little is known about the development of schizophrenia in intercountry adoptees, a group with potentially increased vulnerability. The aim of this study was to investigate the risk of developing schizophrenia in adoptees and in non‐adoptees. Methods:  Utilising data from the Danish Civil Registration System, we established a population‐based cohort of 1.06 million persons resident in Denmark before the age of 15, whose legal mother lived in Denmark at the child's birth. Intercountry adoptees were identified as children born abroad. Record linkage provided information on psychiatric admissions. Results:  Intercountry adoptees had an increased relative risk (RR) (RR = 2.90, 95% CI 2.41–3.50) of developing schizophrenia compared to native Danes. The increased risk was independent of age at onset and age at, or region of, adoption, and was not attributable to mental illness in a foster parent, the foster parent's age, or to urbanisation. The foster mother's own biological offspring had also an increased risk of developing schizophrenia (1.92, 95% CI 1.23–3.02). Conclusions:  Young adult intercountry adoptees are at increased risk for schizophrenia. Although the underlying cause is unknown, a complex interplay of factors presumably may be involved, including heredity, adversity prior to adoption, and post‐adoption adjustment difficulties during upbringing.

Objective: To investigate recent evidence suggesting that social factors are causally related to the development of schizophrenia. Method: I conducted a sytematic review of MEDLINE to identify possibly relevant studies. The search was limited to peer-reviewed studies and review articles appearing in English-language journals since 1996. Studies were included if they used standardized diagnostic criteria for schizophrenia or standardized assessment instruments for psychotic symptoms. Results: Studies of migrants to western Europe provide compelling support for the notion that social factors contribute to the development of schizophrenia. Findings such as excessively high risk for schizophrenia in second-generation immigrants are difficult to explain solely in terms of biological or genetic factors. A growing number of studies implicate childhood exposure to social adversity as a risk factor for schizophrenia, although few studies have used prospective designs. The increased incidence of schizophrenia risk associated with urban birth and (or) urban upbringing suggests possible social causation, but these findings are more ambiguous. Thus far, no studies have explored actual mechanisms by which exposure to social factors might generate psychotic symptoms, although animal experiments suggest that social defeat or social exclusion may cause dopamine dysregulation or sensitization. Conclusions: The accumulating evidence suggesting a role for social factors in the development of schizophrenia arises primarily from studies of migrants conducted in Europe. The mechanisms by which social factors exert their influence remain unknown. Future investigations of social causation should clarify the temporal relation between exposure to social defeat and (or) social adversity and the development of psychotic symptoms.

Background. Urban birth, a risk factor for schizophrenia, is more frequent among second-generation immigrants. The aim of the current study was to determine whether the increased risk for schizophrenia found in second-generation immigrants is explained by the degree of urbanization of birthplace and/or factors related to parentage, such as geographic origin or history of residence abroad during upbringing. Method. Using data from the Danish Civil Registration System (CRS), we established a population-based cohort of 2·0 million Danes (persons born in Denmark). Schizophrenia in cohort members was identified by cross-linkage with the Danish Psychiatric Central Register. Results. The relative risk of developing schizophrenia was 1·93 [95% confidence interval (CI) 1·79–2·08] and 2·96 (95% CI 2·49–3·51) among persons with one or both parents foreign-born respectively compared to native Danes. Adjustment for urbanization of birthplace and parental characteristics reduced these risks slightly. However, urbanization had a lesser effect in second-generation immigrants than in Danes. History of residence abroad was a risk factor for schizophrenia, regardless of whether parents were foreign-born or native Danes. Conclusion. The increased risk found in second-generation immigrants cannot be explained by urbanization or parental characteristics pertaining to age, mental illness, geographic origin or residence abroad during a child's upbringing.