Objectives We described the population of people who frequently use ED for mental disorders, delineating differences by the number of visits for substance use disorders (SUDs), and predicted the receipt of follow-up services and 2-year mortality by the level of ED use for SUD.

Methods This retrospective observational study included all Ontario residents 15 years and older who had five or more ED visits during any 12-month period from 2010 to 2012 (n=263 346). The study involved a secondary analysis of administrative health databases capturing emergency, hospital and ambulatory care. Frequent ED users for mental disorders (n=5416) were grouped into nested categories based on the number of ED visits for SUD. Logistic regression was used to examine group differences in the receipt of follow-up services and mortality, controlling for sociodemographics, comorbidities and past service use.

Results The majority of frequent ED users for mental disorders had at least one ED visit for SUD, most commonly involving alcohol. Relative to people with no visits for SUD, those with ED visits for SUD were older and more likely to be men (Ps <0.001). As the number of ED visits for SUD increased, the likelihood of receiving follow-up care, particularly specialist mental healthcare, declined while 2-year mortality steadily increased (Ps <0.001). These associations remained after controlling for comorbidities and past service use.

Conclusions Findings highlight disparities in the receipt of specialist care based on use of ED services for SUD, coupled with a greater mortality risk. There is a need for policies and procedures to help address unmet needs for care and to connect members of this vulnerable subgroup with services that are better able to support recovery and improve survival.