Exploring indigenous ethnic inequities in first episode psychosis in New Zealand - A national cohort study

Introduction: First episode psychosis (FEP) disproportionately affects rangatahi (young) Maori, the Indigenous people of New Zealand, but little is known about factors contributing to this inequity. This study describes a cohort of rangatahi Maori and young non-Maori with FEP, and explores ethnic differences in incidence rates, and the contribution of deprivation, urbanicity and substance use. Methods: Maori and young non-Maori, aged 13-25 at the time of the first recorded psychosis-related diagnoses, were identified from within Statistics NZ's Integrated Data Infrastructure (IDI), between 2009 and 2012. To estimate age-standardised FEP incidence rates, the population-at-risk was estimated using IDI-based usual resident population estimates for 2009-2012, stratified by ethnicity and single year of age. Poisson regression models were used to estimate ethnic differences in FEP incidence adjusted for age, gender, deprivation, and urban-rural area classification. Results: A total of 2412 young people with FEP (40% Maori, 60% non-Maori) were identified. Maori were younger, and more likely to live in deprived and rural communities and be diagnosed with schizophrenia. Substance induced psychosis was uncommon. The unadjusted age-standardised FEP incidence rate ratio was 2.48 (95% CI: 2.29-2.69) for rangatahi Maori compared with young non-Maori. While adjusting for age, sex, deprivation and urban rural area classification reduced ethnic differences in incidence, rangatahi Maori were still more than twice as likely to have been diagnosed with FEP compared to young non-Maori. Conclusions: This study confirms previous findings of elevated rates of psychosis among rangatahi Maori. The difference in rates between Maori and non-Maori were attenuated but remained after adjustment for deprivation and urbanicity. (C) 2020 Elsevier B.V. All rights reserved.