Quantifying the size of the informal care sector for Australian adults with mental illness: caring hours and replacement cost.

PURPOSE: To quantify and value the total informal support provided by family and friends to Australian adults with mental illness in 2018. METHODS: The number of mental health carers was drawn from the 2015 Survey of Disability, Ageing and Carers (SDAC), adjusted to the 2018 population. Annual caring hours by type of assistance were estimated using the SDAC, 2007 National Survey of Mental Health and Wellbeing and an online carer survey. Caring hours for each task were assigned an hourly replacement cost from the National Disability Insurance Scheme. Informal caring was valued as the sum of these costs minus expenditure on carer income support payments, estimating how much it would hypothetically cost governments to replace this care with formal support services. RESULTS: An estimated 354,000 (95% uncertainty interval (UI): 327,000-383,000) Australian mental health carers provided 186 million (95% UI: 159-215) hours of support in 2018. The estimated replacement cost was AU$8.4 billion (95% UI: 7.0-10.0), excluding AU$1.3 billion in income support. Univariate sensitivity analyses demonstrated that results were robust to variation in model inputs, with total caring hours the most influential parameter. Using an alternative estimate of mean caring hours, the replacement cost could be as high as AU$13.2 billion (95% UI: 11.2-15.4). CONCLUSION: Informal carers provide substantial support to people with mental illness, highlighting their important contribution to the mental health system and reinforcing the need for carer support services. Future valuation studies would benefit from refinement of available data collections, particularly on hours and types of care provided.