Long-term effect of psychological trauma on the mental health of Vietnamese refugees resettled in Australia: a population-based study

Background What are the deleterious effects of mass trauma on the psychological wellbeing of refugees and other war-affected populations? Most epidemiological data are for short-to-medium term effects, leaving the possibility that early psychological reactions could reduce naturally over time. We aimed to assess the long-term effects of trauma on mental health and disability in Vietnamese refugees resettled in Australia. Methods In a population-based study, we identified a community sample of 1413 adult Vietnamese from census collection areas in Sydney, Australia. Participants were interviewed by trained bilingual workers who administered questionnaires to assess the frequency of international classification of disease, version 10 (ICD-10) mental disorders in the 12 months before interview; psychiatric symptoms, by use of a culturally-sensitive symptom measure; exposure to psychologically traumatic events; disability and use of health services; and social, economic, and cultural factors since migration. We did multivariate analyses with adjustment for stressors since migration to establish the risk factors for mental illness. Findings 1161 (82%) adults completed the interview. Mean length of residence in Australia was 11.2 years (SD 14.4) and mean time since the most severe traumatic event was 14.8 years (SD 10.8). 95 (8%) and 75 (7%) of participants had mental disorders defined by ICD-10 and the culturally-sensitive measure, respectively. Trauma exposure was the most important predictor of mental health status. Risk of mental illness fell consistently across time. However, people who had been exposed to more than three trauma events (199) had heightened risk of mental illness (23, [12%]) after 10 years compared with people with no trauma exposure (13, [3%]) (odds ratio 4.7, p<0.0001, 95% CI 2.3-9.5). Interpretation Most Vietnamese refugees were free from overt mental ill health. Trauma-related mental illness seemed to reduce steadily over time, but a subgroup of people with a high degree of exposure to trauma had long-term psychiatric morbidity. Our findings support the need to develop specialised mental health services to reduce disability in refugees whose exposure to extreme trauma puts them at risk of chronic psychiatric disability.