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- Cantor-Graae, Elizabeth, et al.
(author)
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Schizophrenia and migration: a meta-analysis and review.
- 2005
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In: American Journal of Psychiatry. - 1535-7228. ; 162:1, s. 12-24
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Research review (peer-reviewed)abstract
- OBJECTIVE: The authors synthesize findings of previous studies implicating migration as a risk factor for the development of schizophrenia and provide a quantitative index of the associated effect size. METHOD: MEDLINE was searched for population-based incidence studies concerning migrants in English-language publications appearing between the years 1977 and 2003. Article bibliographies and an Australian database were cross-referenced. Studies were included if incidence reports provided numerators and denominators and if age correction was performed or could be performed by the authors. Relative risks for migrant groups were extracted or calculated for each study. Significant heterogeneity across studies indicated the need for a mixed-effects meta-analytic model. RESULTS: The mean weighted relative risk for developing schizophrenia among first-generation migrants (40 effect sizes) was 2.7 (95% confidence interval [CI]=2.3–3.2). A separate analysis performed for second-generation migrants (seven effect sizes) yielded a relative risk of 4.5 (95% CI=1.5–13.1). An analysis performed for studies concerning both first- and second-generation migrants and studies that did not distinguish between generations (50 effect sizes) yielded a relative risk of 2.9 (95% CI=2.5–3.4). Subgroup comparisons yielded significantly greater effect sizes for migrants from developing versus developed countries (relative risk=3.3, 95% CI=2.8–3.9) and for migrants from areas where the majority of the population is black (relative risk=4.8, 95% CI=3.7–6.2) versus white and neither black nor white. CONCLUSIONS: A personal or family history of migration is an important risk factor for schizophrenia. The differential risk pattern across subgroups suggests a role for psychosocial adversity in the etiology of schizophrenia.
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| 2. |
- Selten, Jean-Paul, et al.
(author)
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Hypothesis: social defeat is a risk factor for schizophrenia?
- 2007
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In: British Journal of Psychiatry. - : Royal College of Psychiatrists. - 0007-1250 .- 1472-1465. ; 191, s. 9-12
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Journal article (other academic/artistic)abstract
- The increased schizophrenia risks for residents of cities with high levels of competition and for members of disadvantaged groups (for example migrants from low- and middle-income countries, people with low IQ, hearing impairments or a history of abuse) suggest that social factors are important for aetiology, Dopaminergic dysfunctioning is a key mechanism in pathogenesis. This editorial is a selective literature review to delineate a mechanism whereby social factors can disturb dopamine function in the brain. Experiments with rodents have shown that social defeat leads to dopaminergic hyperactivity and to behavioural sensitisation, whereby the animal displays an enhanced behavioural and dopamine response to dopamine agonists. Neuroreceptor imaging studies have demonstrated the same phenomenain patients with schizophrenia who had never received antipsychotics, In humans, the chronic experience of social defeat may lead to sensitisation (and/or increased baseline activity) of the mesolimbic dopamine system and thereby increase the risk for schizophrenia. Declaration of interest None.
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| 3. |
- Selten, Jean-Paul, et al.
(author)
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Migration and schizophrenia.
- 2007
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In: Current Opinion in Psychiatry. - 0951-7367. ; 20:2, s. 111-115
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Journal article (peer-reviewed)abstract
- Purpose of review An exploration of the evidence that a history of migration is a risk factor for schizophrenia and an evaluation of those studies that seek an explanation for this. Recent findings A meta-analysis found an increased risk for schizophrenia among first-generation and second-generation migrants and found a particularly high risk for migrants from countries where the majority of the population was Black. The latter finding was confirmed and extended by a large first-contact incidence study in the UK, which found excessive risks for schizophrenia and mania in the African-Caribbean and black-African sections of the population. A very high risk of schizophrenia has also been reported for Moroccan males in the Netherlands. The explanation for these findings is uncertain. Social adversity, racial discrimination, family dysfunction, unemployment and poor housing conditions have been proposed as contributing factors. Summary A personal of family history of migration is a high risk factor for schizophrenia and there is now evidence against selective migration as the explanation. There is an increasing interest in the impact of social stressors on brain functioning and on the pathogenesis of schizophrenia.
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| 4. |
- Selten, Jean-Paul, et al.
(author)
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The Social Defeat Hypothesis of Schizophrenia: An Update
- 2013
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In: Schizophrenia Bulletin. - : Oxford University Press (OUP). - 1745-1701 .- 0586-7614. ; 39:6, s. 1180-1186
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Journal article (peer-reviewed)abstract
- According to the social defeat (SD) hypothesis, published in 2005, long-term exposure to the experience of SD may lead to sensitization of the mesolimbic dopamine (DA) system and thereby increase the risk for schizophrenia. The hypothesis posits that SD (ie, the negative experience of being excluded from the majority group) is the common denominator of 5 major schizophrenia risk factors: urban upbringing, migration, childhood trauma, low intelligence, and drug abuse. The purpose of this update of the literature since 2005 is to answer 2 questions: (1) What is the evidence that SD explains the association between schizophrenia and these risk factors? (2) What is the evidence that SD leads to sensitization of the mesolimbic DA system? The evidence for SD as the mechanism underlying the increased risk was found to be strongest for migration and childhood trauma, while the evidence for urban upbringing, low intelligence, and drug abuse is suggestive, but insufficient. Some other findings that may support the hypothesis are the association between risk for schizophrenia and African American ethnicity, unemployment, single status, hearing impairment, autism, illiteracy, short stature, Klinefelter syndrome, and, possibly, sexual minority status. While the evidence that SD in humans leads to sensitization of the mesolimbic DA system is not sufficient, due to lack of studies, the evidence for this in animals is strong. The authors argue that the SD hypothesis provides a parsimonious and plausible explanation for a number of epidemiological findings that cannot be explained solely by genetic confounding.
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