Trends and determinants of mental illness in humanitarian migrants resettled in Australia: Analysis of longitudinal data

Given the frequent exposure of humanitarian migrants to traumatic or stressful circumstances, there exists a potential predisposition to mental illness. Our objective was to pinpoint the trends and determinants of mental illness among humanitarian migrants resettled in Australia. This study considered five waves of longitudinal data involving humanitarian migrants resettled in Australia. Post-traumatic stress disorder (PTSD) and psychological distress were assessed using PTSD-8 and Kessler-6 screening tools. Through a Generalised Linear Mixed model (GLMM), variables displaying a 95% CI that excluded the value of 1.0 for the odds ratio were identified as associated factors for both PTSD and elevated psychological distress. The selection of multivariable covariates was guided by causal loop diagrams and least absolute shrinkage and selection operators methods. At baseline, there were 2399 humanitarian migrants with 1881 retained and at the fifth yearly wave; the response rate was 78.4%. PTSD prevalence decreased from 33.3% (95% CI: 31.4–35.3) at baseline to 28.3% (95% CI: 26.2–30.5) at year 5. Elevated psychological distress persisted across all waves: 17.1% (95% CI: 15.5–18.6) at baseline and 17.1% (95% CI: 15.3–18.9) at year 5. Across the five waves, 34.0% of humanitarian migrants met screening criteria for mental illness, either PTSD or elevated psychological distress. In the multivariate model, factors associated with PTSD were loneliness (AOR 1.5, 95% CI: 1.3–1.8), discrimination (AOR 1.6: 1.2–2.1), temporary housing contract (AOR 3.7: 2.1–6.7), financial hardship (AOR 2.2:1.4–3.6) and chronic health conditions (AOR 1.3: 1.1–1.5), whereas the associated factors for elevated psychological distress were loneliness (AOR 1.8: 1.5–2.2), discrimination (AOR 1.7: 1.3–2.2) and short-term lease housing (AOR 1.6: 1.0–1.7). The prevalence, persistence and consequential burden of mental illness within this demographic underscore the urgent need for targeted social and healthcare policies. These policies should aim to mitigate modifiable risk factors, thereby alleviating the significant impact of mental health challenges on this population.