British Columbia (BC) has witnessed an alarming surge in accidental opioid overdoses in recent years. This public health crisis has raised great concern among healthcare providers, policymakers, and researchers attempting to decipher the repercussions of these overdoses and ways to mitigate the aftermath.

A retrospective cohort study published in BMJ Open [1] sought to examine the association between accidental opioid overdoses in BC and the risk of various neurological, respiratory, cardiac, and other adverse events. The key question was whether these risks were amplified during hospital readmissions in comparison to initial admissions.


Study Design and Population

The research by Morrow et al. (2020) entailed a retrospective cohort study using linked administrative data from BC, Canada. The primary analysis encompassed 2433 patients with 2554 admissions for accidental opioid overdose between 2006 and 2015, which included 121 readmissions within a year of the initial admission. Additionally, a secondary analysis drew on a comparison between 538 patients discharged after accidental opioid overdose hospitalization and 11,040 matched controls from a cohort of patients with at least 180 days of prescribed opioid use.

Outcome Measures

The primary adverse event studied was encephalopathy, with secondary outcomes including adult respiratory distress syndrome, respiratory failure, pulmonary hemorrhage, aspiration pneumonia, cardiac arrest, ventricular arrhythmia, heart failure, rhabdomyolysis, paraplegia or tetraplegia, acute renal failure, and death. A composite outcome encompassed encephalopathy or any secondary outcome plus total serious adverse events, incorporating all-cause hospitalization or death.


Admissions Involving Encephalopathy and Adverse Events

Results indicated that only 3% of accidental opioid overdose admissions included encephalopathy and 25% had one or more adverse events (composite outcome). Intriguingly, the research found no evidence of increased risk of encephalopathy (OR 0.57; 95% CI 0.13 to 2.49) or other outcomes during readmissions as opposed to initial admissions.

In the secondary analysis, fewer than five patients in each cohort experienced encephalopathy. Nevertheless, the risk of composite outcomes (OR 2.15; 95% CI 1.48 to 3.12) and all-cause mortality (OR 2.13; 95% CI 1.18 to 3.86) were considerably higher for patients in the year following an overdose compared with controls.

Implication of Results

These findings challenge the prevailing assumption that patients are at greater risk of adverse events during readmissions after an accidental opioid overdose. However, they undeniably suggest that serious morbidity and mortality risks are elevated in the year post-overdose.


Morrow et al.’s study ‘[Outcomes associated with hospital admissions for accidental opioid overdose in British Columbia: a retrospective cohort study][1]’ emphasizes the sobering long-term impacts of opioid overdoses. It underscores the importance of post-discharge follow-up and the necessity for more comprehensive addiction treatment and recovery support services.

Policy Implications and Recommendations

Given the gravity of opioid-related harm, BC’s provincial health officer declared a public health emergency in 2016 [2]. The aftermath of overdose episodes demonstrates a need for strategies targeting the prevention of initial overdoses and better management of patients post-overdose to reduce recurrence and subsequent adverse outcomes.

Future Research and Limitations

The authors recognize the limitations of their study, such as the reliance on administrative datasets, which might not capture the breadth of clinical nuances. Future research should focus on qualitative data to unpack the personal and social dimensions affecting overdose risk and recovery journeys, as well as the evaluation of intervention efficacy.


Morrow et al. add an important piece to the opioid overdose puzzle. With BC and other regions grappling with this health crisis, such research helps inform more effective medical and policy responses.

This study is a reminder of the complexity of the opioid overdose issue and the diverse consequences that stretch beyond the initial event.


1. Morrow RL, Bassett K, Maclure M, Dormuth CR. Outcomes associated with hospital admissions for accidental opioid overdose in British Columbia: a retrospective cohort study. BMJ Open. 2019;9(5):e025567. (

2. Government of British Columbia. Provincial health officer declares public health emergency 2016. Accessed via: [](


1. Opioid Overdose British Columbia
2. Accidental Opioid Overdose Hospital Admissions
3. Opioid Overdose Health Outcomes
4. Encephalopathy Opioid Overdose Risk
5. Opioid Overdose Mortality Study