Hospital emergency departments (EDs) play an integral role in the care of people with mental health (MH) problems – they are sought for and provide an initial point of access to the MH system, care during a crisis or as a destination for after-hours MH care.[1], [2], [3] The number of people presenting to EDs with MH diagnoses has increased in recent years in Australia and overseas.[4], [5], [6], [7], [8], [9], [10] Growth in MH presentations has exceeded that of total ED presentations;[6] Australia-wide between 2011/12 and 2018/9, MH presentations as a proportion of all ED presentations increased from 2.9% to 3.6%.[11] The flow-on requirements of ED presentations by people with MH diagnoses on staff, other patients and the overall health system is likely to intensify as demand for MH ED services continues to rise.

The ‘distinctive profile’ of people with MH diagnoses presenting to ED[12], [13] requires that their characteristics be compared to those of their non-MH counterparts to enhance our understanding of who they are. Heightened awareness and understanding of differences can inform procedures and education programs aimed at improving ED service delivery and patient outcomes.[14], [15].

Quality patient care and meeting mandated targets require continual quality improvement processes.[12] Significant variations between hospitals within the state of Victoria in the characteristics and care of people with MH diagnoses presenting to ED[3] highlight the importance of examining local data, rather than relying on aggregated state or national data.[13] Service planning and provision require local information to inform prevention strategies, guide resource allocation and identify shortfalls and areas where changes in systems or processes could achieve improved service and care.

We aimed to describe and compare sociodemographic and presentation characteristics and clinical outcomes of people with MH and non-MH diagnoses presenting to the EDs of a local health service in western Sydney, New South Wales (NSW), Australia, with the goal of uncovering disparities in care. Identified gaps indicate areas for service re-assessment and improvement. To avoid distortion due to the impact of COVID-19[16] the study period ended on 31 December 2019.