Factors associated with mental health representations to the emergency department within six months

•8 % of ED attendees with a mental health (MH) diagnosis represented within 28 days.•16 % represented within 6 months; 11 % represented once, 5 % two or more times.•Leaving ED before completing treatment increased 28-day and 6-month representations.•Self-described MH problem and previous hospitalisation also increased risk.•Risk associated with other factors varied between younger and middle-aged adults. ED representation places a tremendous drain on resources with mental health (MH) representation among the most common. This study aimed to identify patient and clinical factors associated with 28-day and six-month ED MH representation of an index MH ED presentation. All MH related ED presentations from 1 January 2017 to 30 June 2019 were extracted from routinely collected administrative data. Cox regression and multinomial logistic regression models tested associations between patient characteristics and risk of representation. For the 8,010 patients, 28-day and six-month representations were 8 % and 16 % respectively. Self-identifying with a MH problem at index presentation (28-day hazard ratio (HR) = 1.48, 95 % CI = 1.19–1.84; six-month HR = 1.52, 95 % CI = 1.29–1.78), leaving ED before completing treatment (28-day HR = 4.13, 95 % CI = 3.36–5.08; six-month HR = 2.52, 95 % CI = 2.12–2.99), no private health insurance (six-month HR = 1.34, 95 % CI = 1.08–1.66), and hospital admission within one year prior to index (six month MH-related admission vs non-MH, HR = 1.59, 95 % CI = 1.19–2.13) were associated with increased risk of representation. Being uninsured was associated with frequent six-month representation among adults aged 16–39 years (OR = 3.16, 95 %CI = 1.59–6.25). Self-identifying with a MH problem, leaving ED prematurely, being uninsured and prior hospitalisation are areas for in-depth investigation for improved understanding of unplanned representations.