Examining the impact of an accommodation and support intervention in reducing homelessness amongst care leavers in Australia: A hybrid type-1 implementation-effectiveness study using propensity score methods

• The intervention did not reduce homelessness for most participants. • Aboriginal participants experienced worse outcomes than non-Aboriginal participants. • Previously homeless youth benefited more than peers without such history. • Participants found intervention more acceptable than support they received during OOHC. • Aftercare planning practice was a major barrier to implementation. Young people transitioning from out-of-home care (OOHC) face elevated risks of adverse outcomes across multiple domains. Existing interventions have shown small or null effects when rigorously evaluated, highlighting the need to identify effective approaches to supporting care leavers. Evaluate the impact of the Premier’s Youth Initiative (PYI), an accommodation and support intervention, on homelessness outcomes for care leavers and explore its implementation. 295 eligible care leavers who received PYI in New South Wales, Australia between 2017–2020 and a matched comparison group drawn from locations where PYI was unavailable. We undertook a hybrid type-1 implementation-effectiveness study that used linked administrative data from child welfare and homelessness services. Propensity score methods were applied to estimate the average treatment effect on the treated on ten measures of homelessness between ages 18–19. Implementation was explored through focus groups with participants, service providers and the funder to explore intervention acceptability as well as barriers and facilitators. Overall PYI had no impact on any assessed homelessness measures—with treatment effects consistently near zero. Subgroup analyses showed that Aboriginal participants experienced worse outcomes than non-Aboriginal peers. Participants who experienced homelessness during OOHC appeared to benefit more from PYI, relative to those who did not, but estimates were inconsistent. Implementation analysis identified high acceptability among participants but revealed substantial barriers, particularly inadequate planning for leaving care. Interventions like PYI may need to commence earlier, be provided at greater intensity, or be targeted more effectively to the most vulnerable care leavers.