Psychosocial disability in Australia: Prevalence, functional severity and population projections to 2060 from repeated cross-sectional population surveys

BACKGROUND: Existing approaches to estimating psychosocial disability - arising from severe mental illness - rely heavily on diagnostic categories and health service utilisation. By neglecting functional-limitation and participation restriction, such approaches limit the utility of current estimates for planning disability supports. This study addresses that gap by estimating the prevalence, functional severity and projected population counts of psychosocial disability in Australia, aligned with the World Health Organization International Classification of Functioning, Disability and Health framework. METHODS: Using a repeated cross-sectional design, we analysed four waves of the nationally representative Survey of Disability, Ageing and Carers (2009, 2012, 2015, 2018). Psychosocial disability was operationally defined as a long-term mental health condition combined with disability, consistent with the International Classification of Functioning, Disability and Health framework. Survey-weighted prevalence was estimated overall and by functional severity. Pooled age- and sex-specific prevalence rates were then applied to three population growth scenarios to project counts to 2060. RESULTS: Prevalence remained stable at 1.0% across all waves, with population counts rising from ~196,600 (2009) to ~243,800 (2018), reflecting demographic growth. People with psychosocial disability were disproportionately middle-aged, Australian-born, socioeconomically disadvantaged and living outside major cities. Under the medium growth scenario, projected counts increase from ~274,000 (2025) to ~410,000 (2060; +50%), with those experiencing profound limitation projected to nearly double (+92%). CONCLUSION: Shifting from diagnosis- to function-based estimation, this study provides a policy-relevant basis for psychosocial disability planning. Rapid growth in the number of profound psychosocial disability underscores the need for early intervention and coordinated psychosocial supports beyond Australia's National Disability Insurance Scheme.