RESULTADOS Y DISCUSIÓN

In this Chapter, I have suggested that our understanding of causality was based on a mechanistic explanation underpinned by a probabilistic correlation, left room for multiple INUS conditions, and was able to include distant yet salient causes. I suggest the Bradford-Hill criteria are useful to assess likely causality of risk factors. I have argued that ethnicity is not a stable cause for the excess risk of psychosis in ethnic minority groups, as the risk for the same ethnic group varies depending on background conditions such as geographical location. I also argue that whereas pre-migration circumstances and migration itself are undeniably an ingredient of the causal cake, they are unable to account for the increased risk in later- generation migrants who have never themselves migrated.

I subsequently turned to the social sciences to explore the potential of the social circumstances of minorities being a plausible mechanism. I argued that particularly culturally distant minorities were at increased risk of social exclusion or falling outside the group of ‘fellow citizens’, leading to increased social distance. Such an outsider experience that could not be behaviourally avoided increased psychosocial disempowerment, which in turn was hypothesised to increase risk of psychosis.

This account of why minorities are at increased risk of developing psychosis is broad: it is the social and cultural distance and psychosocial disempowerment that are of causal relevance, not the simple fact of having a different ethnic background. This means that this same explanatory framework isn’t necessarily limited to ethnic minorities: in Western societies, they currently occupy a marginalised position. However, so do other minority groups such as Muslims (a religious minority) and non-heterosexual and non-binary people. It is possible that such groups find themselves in a very similar position, if not now, then in the future.

Before I expand on such speculation however, it is prudent to test the plausibility of this explanatory framework in the minority group with the best-established excess psychosis risk: ethnic minorities. I will use data from the case-control arm of the EU-GEI study to do so, and as such am able to look at ethnic minorities across six countries. The empirical details of this are found in the subsequent Chapter (6), where I also explore excess risk in religious minorities. In Chapter 7, I will incorporate the more novel and perhaps

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controversial element of genetic distance. This has been eluded to in the introduction, but will be explained in more detail in the background of Chapter 7.

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- Social and cultural distance as an explanation of higher

rates of psychotic disorders in ethnic minority groups

6.1 Background

Ethnic minorities have a well-established excess risk of psychosis (Anderson et al., 2015; Bourque et al., 2011; Kirkbride, Hameed, Ioannidis, et al., 2017; Tortelli et al., 2014), the causes of which are not well- understood. In Chapters 1 and 5, I discussed that ethnicity itself is not a stable cause, as the risk for specific ethnic groups varies depending on background conditions (Bhugra et al., 1996; Fearon et al., 2006;

Hickling, 1995; Selten et al., 2005; Veling et al., 2006). Whilst pre-migratory factors and migration itself are important, particularly for refugees (Anderson et al., 2015; Hollander et al., 2016), these can’t explain excess risk in second and later generations. In the previous Chapter, I argued that falling outside the group of fellow citizens increases social distance and psychosocial disempowerment, and subsequent risk of psychosis. Those at a larger cultural distance are particularly at risk. In this Chapter, I will test whether cultural distance, social distance and psychosocial disempowerment explain the excess psychosis risk seen in some ethnic minority groups. I will also examine if this sociocultural distance model can explain any excess risk in religious minorities.

There is existing epidemiological evidence supporting the link between indicators of social distance and psychosis. The hypothesis that social isolation increases psychosis risk is long-standing (Faris & Dunham, 1939; Kohn & Clausen, 1955), and has been summarised in a recent systematic review (Gayer-Anderson & Morgan, 2013). Social isolation and educational attainment were elements of Morgan’s concept of cumulative social disadvantage. Both were associated with an increased risk of psychosis and were more common in the Black-Caribbean group (Morgan et al., 2008), increasing their impact on psychosis risk in this group. In a Swedish registry study educational attainment was also shown to be associated with increased risk of being admitted to hospital for a psychotic disorder, after allowing for age, sex, immigrant status and socioeconomic status (hazard ratio (HR) for low education: 1.46, 95%CI: 1.36-1.56)(Leão, Sundquist, Johansson, Johansson, & Sundquist, 2005). Educational attainment possibly moderated psychosis risk in second-generation migrants (Leão et al., 2005). Higher IQ and other makers of cognitive ability have also been conceptualised as evidence of cognitive reserve, which may be protective against psychosis (Khandaker et al., 2011). There are other influences on educational attainment (notably, socio- economic status and parental education (Putnam, 2015)), suggesting it is both a suitable indicator of social distance and determinant of psychosis risk.

The majority of evidence for the importance of psychosocial disempowerment in psychosis risk is derived experimentally, under a social stress paradigm (Akdeniz, Tost, Streit, et al., 2014; Howes et al., 2017; Lederbogen et al., 2011; Mizrahi et al., 2012; Van Winkel, Stefanis, & Myin-Germeys, 2008), but it has some epidemiological support (Berg et al., 2011.; Karlsen, Nazroo, McKenzie, Bhui, & Weich, 2005; Veling

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et al., 2007; Veling, Hoek, et al., 2008). For instance, a Dutch incidence study demonstrated a relationship between perceived discrimination and increased incidence at population-level (Veling et al., 2007), but not at individual level in a case-control sample (Veling, Hoek, et al., 2008). In a cross-sectional study

investigating psychiatric illness in the community, experiences of interpersonal racism and perceptions of racism in society as whole were associated with an increased risk of psychosis, after controlling for age, sex and socioeconomic status (Karlsen et al., 2005).

The introduction of cultural distance is theoretical and innovative, and as such no studies have sought to operationalise and investigate this construct in the context of psychiatric epidemiology. A justification for using language distance and fluency in the majority language as proxies was given in Section 5.4. As detailed in Section 5.2, psychotic disorders are multi-causal and this PhD seeks to identify one element of the causal cake. Other elements of the cake include socioeconomic status (Marwaha & Johnson, 2004; Werner, Malaspina, & Rabinowitz, 2007), childhood trauma (Bendall et al., 2008; Matheson et al., 2012; Varese et al., 2012), cannabis use (Manrique-Garcia et al., 2012; Moore et al., 2007), younger age, male sex and their interaction (Häfner et al., 1993; Thorup et al., 2007)(Chapter 4), as well as increased paternal age at birth (Sipos et al., 2004; Zammit et al., 2003). These elements might confound the relationship between ethnic minority status and psychosis (line A in Figure 6.1), confound the relationship between social distance and psychosis (line B) or independently predict psychosis risk. In this Chapter, I seek to identify the unique contribution of social distance, cultural distance, and psychosocial disempowerment, and to determine if their combination is the missing ingredient in the causal cake of higher rates of psychosis in ethnic minorities.

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As mentioned in Chapter 5, this model is not necessarily limited to ethnic minorities and I will also explore whether this model applies to religious minorities (those who follow a non-Christian religion). The yield from the literature on religion and psychosis is limited: a PubMed search using the terms

((psychosis[Title/Abstract] OR schizophrenia [Title/Abstract]) AND (religion [Title/Abstract])), yielded 130 articles. Most of these dealt with religious content of hallucinations and delusions (Gearing et al., 2011), or looked at the role of religion for social support (Sariah, Outwater, & Malima, 2014; Tabak & de Mamani, 2014). A multi-national study looking at spirituality and religion showed that religious involvement was higher in outpatients with schizophrenia or schizoaffective disorder compared with the general population (Mohr et al., 2012). Data from the Adult Psychiatric Morbidity Survey showed that non-Christians reported increased religious discrimination, and that those who perceived religious discrimination had an increased prevalence of common mental disorders (Jordanova, Crawford, McManus, Bebbington, & Brugha, 2015). Both of these studies were cross-sectional, the first study was small (n=276 )(Mohr et al., 2012), and the

Social distance Cultural distance Psychosocial disempower- ment Psychosis Confounding factors Independent predictors Ethnic minority status

A

B

The blue lines are hypothesised to explain the observed association represented by the red line. Line A represents covariates confounding the association between ethnic minority status and psychosis, and line B represents covariates confounding the association between social distance and psychosis.

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Adult Psychiatric Morbidity Survey looked at common mental disorders more broadly as opposed to psychosis specifically (Jordanova et al., 2015). This topic has not been well-researched, thus far.