Background Traumatic brain injury (TBI) is a leading cause of mortality and disability worldwide and may be particularly prevalent among homeless or unstably housed people. Research on TBI among homeless populations has been conducted predominantly in North America; TBI among homeless Australians has not been investigated.

Objective To ascertain the prevalence of self-reported TBI among a national sample of homeless Australians.

Methods Agencies providing homelessness services administer the Vulnerability Index Service Prioritization Decision Assistance Tool (VI-SPDAT) in Australia’s four largest cities (i.e., Brisbane, Sydney, Melbourne, Perth). The VI-SPDAT is a self-report survey that queries physical and mental health, substance use, and housing needs. Lifetime history of TBI is assessed by a single item that asks respondent if they have ‘had a serious brain injury or head trauma?’ Data collection is coordinated by community organisations and the Australian Alliance to End Homelessness. We consolidated 2010–2017 surveys into a dataset comprised of 8360 unique respondents.

Findings Adult respondents had an average age of 44 years (SD=13), 67% identified as male, and most did not complete high school (73%). Indigenous Australians were over-represented relative to the general population (24% vs 3%). Six percent of respondents identified as LBGTQ+, 7% were veterans, and 41% reported most often sleeping rough (e.g., streets, park, car). Twenty-nine percent of respondents endorsed a history of TBI, with higher rates among rough sleepers, veterans, and those with tri-morbidity (i.e., co-occurring physical, mental and substance use problems); 34%, 43%, and 43%, respectively.

Conclusion and policy implications Our findings suggest that TBI is common among homeless Australians. Brain injury may yield persistent challenges (e.g., cognitive impairment) that make exiting homelessness difficult, and community supports may be inadequately prepared to support individuals who are living with the sequelae of brain injury. Recommendations for future research and policy considerations will be discussed.