Importance: This systematic review and meta-analysis is, to date, the first and most comprehensive to focus on the incidence of nonaffective psychoses among refugees.
Objective: To assess the relative risk (RR) of incidence of nonaffective psychosis in refugees compared with the RR in the native population and nonrefugee migrants.
Data sources: PubMed, PsycINFO, and Embase databases were searched for studies from January 1, 1977, to March 8, 2018, with no language restrictions (PROSPERO registration No. CRD42018106740).
Study selection: Studies conducted in Denmark, Sweden, Norway, and Canada were selected by multiple independent reviewers. Inclusion criteria were (1) observation of refugee history in participants, (2) assessment of effect size and spread, (3) adjustment for sex, (4) definition of nonaffective psychosis according to standardized operationalized criteria, and (5) comparators were either nonrefugee migrants or the native population. Studies observing ethnic background only, with no explicit definition of refugee status, were excluded.
Data extraction and synthesis: The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) and the Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines were followed for extracting data and assessing data quality and validity as well as risk of bias of included studies. A random-effects model was created to pool the effect sizes of included studies.
Main outcomes and measures: The primary outcome, formulated before data collection, was the pooled RR in refugees compared with the nonrefugee population.
Results: Of the 4358 screened articles, 9 studies (0.2%) involving 540 000 refugees in Denmark, Sweden, Norway, and Canada were included in the analyses. The RR for nonaffective psychoses in refugees was 1.43 (95% CI, 1.00-2.05; I2 = 96.3%) compared with nonrefugee migrants. Analyses that were restricted to studies with low risk of bias had an RR of 1.39 (95% CI, 1.23-1.58; I2 = 0.0%) for refugees compared with nonrefugee migrants, 2.41 (95% CI, 1.51-3.85; I2 = 96.3%) for refugees compared with the native population, and 1.92 (95% CI, 1.02-3.62; I2 = 97.0%) for nonrefugee migrants compared with the native group. Exclusion of studies that defined refugee status not individually but only by country of origin resulted in an RR of 2.24 (95% CI, 1.12-4.49; I2 = 96.8%) for refugees compared with nonrefugee migrants and an RR of 3.26 (95% CI, 1.87-5.70; I2 = 97.6%) for refugees compared with the native group. In general, the RR of nonaffective psychosis was increased in refugees and nonrefugee migrants compared with the native population.
Conclusions and relevance: Refugee experience appeared to be an independent risk factor in developing nonaffective psychosis among refugees in Denmark, Sweden, Norway, and Canada. These findings suggest that applying the conclusions to non-Scandinavian countries should include a consideration of the characteristics of the native society and its specific interaction with the refugee population.