# Nationwide study of emergency care quality for patients with substance use disorders and dual diagnoses across three distinct patient populations

## TL;DR

This study found that patients with substance use disorders, mental illness, or both receive lower quality emergency care and have worse outcomes compared to others.

## Contribution

The study is the first to compare emergency care quality across three distinct patient populations with mental illness, substance use disorders, and dual diagnoses on a nationwide scale.

## Key findings

- Patients with mental illness or substance use disorders had higher rates of repeat EMS calls and unplanned hospital visits.
- Stroke patients with these conditions were less likely to receive reperfusion therapy.
- Mental illness was linked to longer delays in surgery and reduced survival time after emergency surgery.

## Abstract

Substance use disorders and mental illness increase morbidity and mortality, particularly among patients with coexisting mental illness and substance use (dual diagnoses). This study evaluated the quality of prehospital care (Emergency Medical Services (EMS)) and emergency care for two time-dependent conditions among patients with mental illness, substance use disorders, and dual diagnoses.

We analysed data from three nationwide Danish registries: 1) Danish Prehospital Registry (2016–2017), 2) Danish Stroke Registry (2010–2018), and 3) Danish Registry of Emergency Surgery (2008–2018), supplemented by national health and social registries. Quality of care was assessed using predefined metrics from the clinical registries. Exposure groups included patients with (a) mental illness, (b) substance use disorders, and (c) dual diagnoses, compared with a reference group without either diagnosis.

We identified 492,388 EMS calls, 89,148 admissions with ischemic stroke, and 3,223 emergency surgeries for perforated ulcers. Mental illness, substance use disorders, and dual diagnoses were most prevalent in the EMS cohort (10%, 9%, and 8%, respectively).

Compared with reference patients, EMS patients with mental illness, substance use, or dual diagnoses were more likely to make repeat EMS calls within 24 h (RR 1.60 [1.39–1.83], 2.32 [2.02–2.66], and 3.24 [2.89–3.53]) and have unplanned hospital visits within seven days after EMS-release at scene, i.e. patient weas not transported to the hospital (scene release) (RR 1.50 [1.39–1.62], 1.58 [1.45–1.73], and 2.50 [2.31–2.71]).

Stroke patients with mental illness, substance use, or dual diagnoses were less likely to receive reperfusion therapy for ischemic stroke (RR 0.80 [0.74–0.86], 0.60 [0.54–0.66], and 0.69 [0.60–0.80]) but had rates of other guideline-based stroke care like the reference group without mental illness or substance abuse.

Compared with the reference population, patients with perforated ulcers and mental illness experienced a longer time to surgery, with a delay of 82 min (95% CI: 37–128). Within the first 90 days after surgery, patients were 69 days (IQR [0;83]) alive-and-out-of-hospital; however, patients with mental illness, substance use and dual diagnoses lost a median of 4 days (IQR [-1;9]), 6 days [1;10], and 7 days [0;13], respectively, due to early mortality compared with the reference.

Disparities in prehospital and emergency care were identified across three distinct cohorts: a broad EMS population and two time-critical conditions. Patients with mental illness, substance use disorders, and dual diagnoses faced inequities in EMS response, reperfusion therapy, surgical timeliness contributing to poorer short-term outcomes. However, areas of consistent care quality were observed, particularly in guideline-based stroke care.

The online version contains supplementary material available at 10.1186/s12888-025-06712-8.