Abstract
An 'ethnic' or 'group' density effect in psychosis has been observed, whereby the risk of psychosis in minority group individuals is inversely related to neighbourhood-level proportions of others belonging to the same group. However, there is conflicting evidence over whether this effect differs between minority groups and limited investigation into other moderators. To conduct a comprehensive systematic review and meta-analysis of the group density effect in psychosis and examine moderators. Four databases were systematically searched. A narrative review was conducted and a three-level meta-analysis was performed. The potential moderating effect of crudely and specifically defined minority groups was assessed. Country, time, area size and whether studies used clinical or non-clinical outcomes were also tested as moderators. Thirty-two studies were included in the narrative review and ten in the meta-analysis. A 10 percentage-point decrease in own-group density was associated with a 20% increase in psychosis risk (OR = 1.20, 95% CI 1.09-1.32, P < 0.001). This was moderated by crudely defined minority groups (F6,68 = 6.86, P < 0.001), with the strongest associations observed in Black populations, followed by a White Other sample. Greater heterogeneity was observed when specific minority groups were assessed (F25,49 = 7.26, P < 0.001). This is the first review to provide meta-analytic evidence that the risk of psychosis posed by lower own-group density varies across minority groups, with the strongest associations observed in Black individuals. Heterogeneity in effect sizes may reflect distinctive social experiences of specific minority groups. Potential mechanisms are discussed, along with the implications of findings and suggestions for future research.
Highlights
An ‘ethnic’ or ‘group’ density effect in psychosis has been observed, whereby the risk of psychosis in minority group individuals is inversely related to neighbourhood-level proportions of others belonging to the same group
The overall meta-analytic effect indicated that a 10 percentage-point decrease in group density was associated with a 20% increase in psychosis risk (OR = 1.20, 95% CI 1.09−1.32, P < 0.001)
Moderator tests for specific minority groups showed the strongest associations in Black Antillean migrants in The Netherlands (OR = 3.60, 95% CI 2.22−5.83, P < 0.001) relative to the reference group (‘Combined migrant group’)
Summary
Method Four databases were systematically searchedA narrative review was conducted and a three-level meta-analysis was performed. We followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)[19] and Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines.[20] The protocol for this review was pre-registered on PROSPERO (reference: CRD42019139384). The ethnic density effect in psychosis Search strategy. In May 2019, S.J.B. conducted electronic searches of four databases (PsycINFO, Web of Science, PubMed and CINAHL Plus). We consulted with Bangor University’s academic support librarian for the College of Human Sciences for assistance with designing the search strategies. The search strategies were piloted before the final search was executed. The full list of search terms and an example search strategy for one database can be found in Supplementals 2 and 3. Is an example of the organisation of search terms:
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