By James Ogilvie, Stacy Tzoumakis, Troy Allard, Carleen Thompson, Anna Stewart
This brief is based on the following paper: Ogilvie, J. M., Tzoumakis, S., Allard, T., Thompson, C., Kisely, S., & Stewart, A. (2021). Prevalence of psychiatric disorders for Indigenous Australians: a population-based birth cohort study. Epidemiology and Psychiatric Sciences, 30, e21. doi:10.1017/S204579602100010X
1. What problem does your research address? Why is this significant?
Indigenous Australians experience elevated rates of mental health service usage (AIHW2020), psychological distress (AIHW2015; Jorm, Bourchier, Cvetkovski, & Stewart, 2012), alcohol and/or substance use (O’Leary, Halliday, Bartu, D’Antoine, & Bower, 2013), and hospitalisation rates for self-harm and suicide (Dickson, Cruise, McCall, & Taylor, 2019). Despite these well documented poor mental health outcomes for Indigenous Australians, there are no reliable baseline prevalence rates of specific psychiatric disorder diagnoses for this population. This information is critical to understand the extent of overrepresentation in the health system for Indigenous Australians and inform policy development to better manage health needs. Therefore, the aims of the study were: 1) determine prevalence rates for psychiatric diagnoses for Indigenous Australians admitted to hospital; and 2) examine whether the profile of psychiatric diagnoses for Indigenous Australians are different compared with non-Indigenous Australians. The research is part of a larger project examining the links between mental illness and offending for Indigenous Australians.
2. How did you conduct your research?
We used linked administrative data for a population-based cohort consisting of 45,141 individuals born in Queensland in 1990, with 6.3% of the cohort being Indigenous. The data were drawn from the Queensland Cross-sector Research Collaboration (QCRC) repository established by Professor Anna Stewart (Stewart et al., 2015). This repository includes information linked across multiple government administrative systems for multiple birth cohorts, including information from health, child protection, criminal justice systems, and births, deaths and marriages. The Queensland Government Statistician’s Office (QGSO) and the Queensland Health data linkage unit both made significant contributions in developing the repository.
Queensland Health hospital admissions were used to identify psychiatric disorders between the ages of 4/5 and 23/24 years. We conducted a range of analyses. First, we derived prevalence rates of psychiatric diagnoses for Indigenous and non-Indigenous Australians. Second, we modelled the cumulative prevalence of psychiatric diagnoses by age separately for Indigenous and non-Indigenous Australians. Finally, we used logistic regression analyses to model potential differences between Indigenous and non-Indigenous psychiatric presentations while controlling for socio-demographic characteristics.
3. What are your major findings?
Overall, a very clear picture of Indigenous overrepresentation in psychiatric morbidity was found. By age 23/24 years, Indigenous Australians were diagnosed with psychiatric disorders at a rate over three times that of non-Indigenous Australians (172.16 vs. 54.12 per 1,000). The high rate of psychiatric disorders among Indigenous Australians was consistent with exisiting survey evidence, as well as available statistics demonstrating overrepresentation in most areas of the public health system (AIHW2015; AIHW2018; 2020; Cunningham & Paradies, 2012; Jorm et al., 2012).
Particularly high prevalence rates of substance use disorders were observed for Indigenous Australians (12.2%), and these typically coincided with other disorders. Indigenous psychiatric morbidity started at an earlier age and accelerated at a greater rate up to age 23/24 years when compared with non-Indigenous individuals. This resulted in more pronounced disparities between Indigenous and non-Indigenous Australians as the cohort aged, underscoring the importance of early intervention among vulnerable individuals in Indigenous communities.
Our findings provided further support for the argument that social disadvantage is the driving force behind Indigenous overrepresentation in psychiatric illness, since after adjusting for sociodemographic covariates, differences between Indigenous and non-Indigenous individuals in the likelihood of being diagnosed with a psychiatric disorder disappeared (except for substance use disorders).
4. What does your research mean for policy and practice?
The early onset of psychiatric disorder diagnosis for Indigenous Australians reflects the extreme levels of multiple and accumulated disadvantage faced by Indigenous Australians from an early age that is particularly harmful to psychological health (Twizeyemariya, Guy, Furber, & Segal, 2017) and contributes to the emergence or exacerbation of other social and health problems. To reduce the gap between Indigenous and non-Indigenous Australians in mental health outcomes, social inequality and disadvantage must continue to be addressed through sustained social change efforts and prioritisation in the long-term political agenda. The identified early age of onset for psychiatric diagnosis highlights that mental health services need to be developed and prioritised in childhood and adolescence.
Australian Institute of Health and Welfare. (2015). The health and welfare of Australia’s Aboriginal and Torres Strait Islander people. Retrieved from https://www.aihw.gov.au/reports/indigenous-health-welfare/indigenous-health-welfare-2015/contents/table-of-contents
Australian Institute of Health and Welfare. (2018). Emergency department care 2017–18: Australian hospital statistics (89). Retrieved from Canberra: https://www.aihw.gov.au/reports/hospitals/emergency-department-care-2017-18/contents/table-of-contents
Australian Institute of Health and Welfare. (2020). Mental health services: In brief 2019. Retrieved from Canberra: https://www.aihw.gov.au/reports/mental-health-services/mental-health-services-in-australia
Cunningham, J., & Paradies, Y. C. (2012). Socio-demographic factors and psychological distress in Indigenous and non-Indigenous Australian adults aged 18-64 years: analysis of national survey data. BMC Public Health, 12(1), 95. doi:10.1186/1471-2458-12-95
Dickson, J. M., Cruise, K., McCall, C. A., & Taylor, P. J. (2019). A Systematic Review of the Antecedents and Prevalence of Suicide, Self-Harm and Suicide Ideation in Australian Aboriginal and Torres Strait Islander Youth. Int J Environ Res Public Health, 16(17). doi:10.3390/ijerph16173154
Jorm, A. F., Bourchier, S. J., Cvetkovski, S., & Stewart, G. (2012). Mental health of Indigenous Australians: A review of findings from community surveys. Medical Journal of Australia, 196(2), 118-121. doi:10.5694/mja11.10041
O’Leary, C. M., Halliday, J., Bartu, A., D’Antoine, H., & Bower, C. (2013). Alcohol-use disorders during and within one year of pregnancy: A population-based cohort study 1985-2006. BJOG: An International Journal of Obstetrics and Gynaecology, 120(6), 744-753. doi:10.1111/1471-0528.12167
Stewart, A., Dennison, S., Allard, T., Thompson, C., Broidy, L., & Chrzanowski, A. (2015). Administrative data linkage as a tool for developmental and life-course criminology: The Queensland Linkage Project. Australian & New Zealand Journal of Criminology, 48(3), 409-428. doi:10.1177/0004865815589830
Twizeyemariya, A., Guy, S., Furber, G., & Segal, L. (2017). Risks for Mental Illness in Indigenous Australian Children: A Descriptive Study Demonstrating High Levels of Vulnerability. The Milbank Quarterly, 95(2), 319-357. doi:10.1111/1468-0009.12263
Acknowledgements: We sincerely thank the representatives from the Queensland Government Statistician’s Office, Queensland Health and the Queensland Registry of Births, Deaths and Marriages for the considerable support they provided for this project. The views expressed are not necessarily those of the departments or agencies, and any errors of omission or commission are the responsibility of the authors. The authors gratefully acknowledge use of the services and facilities of the Griffith Criminology Institute’s Social Analytics Lab at Griffith University.