Emergency department use trajectories over a 10-year period among patients with substance-related disorders

Overutilization of the emergency department (ED) is costly and often reflects unmet needs and suboptimal care, raising concerns when patients rely on the ED persistently over many years. Long-term ED use trajectories for patients with substance-related disorders (SRDs) have never been investigated. This study aimed to identify ED use trajectories over a 10-year period and examine associations with patients' sociodemographic and clinical characteristics, quality-of-care indicators, and subsequent adverse outcomes.

A cohort of 9642 patients with long-standing SRDs was examined using Québec (Canada) medical records (1996-2022). Group-Based Trajectory Modeling identified 10-year ED use trajectories. Multinomial logistic regression assessed associations between trajectories and covariates, while Cox models examined links to subsequent adverse outcomes (suicidal behavior, hospitalization, death).

Four ED use trajectories were identified: Trajectory 1 ("Low ED users," 50% of cohort), Trajectory 2 ("Increasing ED users," 20%), Trajectory 3 ("Sinusoidal ED users," 20%), and Trajectory 4 ("Very frequent ED users," 10%). Half of the cohort showed frequent ED use (≥3 visits/year), including 10% who were very frequent users (≥8 visits/year), underscoring substantial unmet needs. ED use frequency was strongly linked to social and health conditions-most favorable in Trajectory 1, who were mostly men, and markedly worse in Trajectories 4, 2, and 3. Adverse outcomes were also strongly associated with poorer social and health conditions and lower treatment motivation, even though Trajectories 4, 2, and 3 received more healthcare services.

Findings indicate that the healthcare system is not adequately structured to meet the needs of patients with severe multimorbidity involving SRDs, mental disorders, chronic physical illnesses, and social instability, contributing to care quality insufficiently meeting the complex needs of Trajectories 2-4. Tailored interventions may be warranted, including Integrated Treatment for Dual Disorders and Assertive Community Treatment for Trajectories 2 and 4, and Intensive Case Management, Recovery Management Checkups, or mobile health technologies for Trajectory 3. Across Trajectories 2-4, enhanced motivational interventions, social support, reduced stigma, optimized medication management, peer-helper programs, and stronger ED-outpatient collaboration remain essential. Improving services for patients with frequent ED use-particularly those in Trajectory 4 with recurrent very frequent use-should be prioritized to reduce costs, optimize service use, and support recovery.