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  • B.C. researchers estimated the risk of brain injury among people who had a drug toxicity event
  • Brain injury was 15 times more likely among people who had experienced drug toxicity than those who had not
  • Enhanced screening after drug toxicity events could improve access to brain injury rehabilitation and support

Brain injury can occur when there is a lack of oxygen to the brain. One way that this may occur is during an opioid-related drug toxicity event (also called an overdose), as people’s breathing is reduced or stopped. Researchers aimed to gain a better understanding of how common brain injuries are among people who have experienced a drug toxicity event and look at the relationship between drug toxicity events and brain injuries among people in British Columbia (B.C.).

Study details

The study sample came from the BC Provincial Overdose Cohort (BC-ODC), which is a linked dataset from multiple data sources in BC. One of the components of the BC-ODC is administrative health data from a 20% random sample of individuals in B.C. who are registered for universal healthcare. A cross-sectional analysis was conducted on this 20% random sample of B.C. residents. Researchers used the linked dataset to identify people who had experienced fatal and non-fatal drug toxicity events and/or been diagnosed with a brain injury between January 1, 2015, and December 31, 2019. They explored the prevalence of brain injury among people who had experienced drug toxicity and analyzed the association between drug toxicity and brain injury.

Study results

A total of 824,165 people were included in the study sample. Of these:

  • A total of 5,357 had experienced at least one drug toxicity event. Of these, 1.0% had a diagnosed brain injury.
  • A total of 369 had experienced a brain injury. Of these, 14.6% had experienced a drug toxicity event.

After adjusting for sex, age and mental illnesses (not including substance use disorder), people who had experienced a drug toxicity event were 15.3 times more likely to have a brain injury than people who had not experienced a drug toxicity event. In both adjusted and unadjusted models, risk of brain injury was higher in people who were aged 40 or older, were male and had been diagnosed with a mental illness.

What are the effects of brain injury?

This study suggests that brain injury is more likely among people who have experienced a drug toxicity event compared to those who have not. Brain injuries due to drug toxicity events can impact people’s memory, speech, vision, ability to concentrate, ability to control behaviour and movement and other abilities. Impacts can range from mild to severe and can lead to coma or death. Symptoms can vary, and they may not appear for several weeks following a drug toxicity event. This means that identification of a brain injury following drug toxicity may be delayed or the injury may remain undiagnosed.

Brain injuries can impact the lives of people who use drugs in many ways, such as by affecting their cognitive abilities and level of independence. They may also increase experiences of stigma and compound existing challenges and barriers for people who use drugs, including access to housing, employment and health and social services.

People who have experienced brain injury can recover, but there may be long-term impacts and people may need a range of supports in the immediate and long term. The researchers of this study stress that a better understanding of the prevalence of brain injury among people who have experienced drug toxicity is important for understanding the types of supports that are needed.

Need to improve screening and care for people with drug toxicity-related brain injury

As the drug toxicity crisis continues, many drug toxicity events are reversed in community settings (e.g., supervised consumption sites, people’s homes) and do not involve interaction with the healthcare system. There is a need for increased awareness and recognition of the potential harms caused by lack of oxygen to the brain during non-fatal drug toxicity events. People who use drugs, frontline harm reduction workers, healthcare providers and other service providers could be provided with training to recognize and screen for symptoms of brain injury among people who have experienced drug toxicity events.

There is a lack of supports available for people who use drugs with brain injury. Programs and services that provide person-centred, harm reduction-oriented outreach and support for people with brain injury should be developed in collaboration with frontline workers and people who use drugs. Such services could help ensure people who have a brain injury are able to access care and supports that can help them in various ways (e.g., to live independently, to recover, to reduce future harms).

Study limitations

This study used a cross-sectional approach to estimate the prevalence of brain injuries among people who had experienced a toxic drug event. As a result, it is not possible to be certain about which of these variables came first. The available research suggests that toxic drug events can lead to brain injury. However, it is unclear whether people who experience drug toxicity are at increased risk of brain injury, whether people with brain injury are at increased risk of drug toxicity, or both.

Many drug toxicity events are reversed in community settings. This means that it is unlikely that all drug toxicity events among people within this sample would have been recorded in this study’s data. In addition, it is likely that the study underestimates the prevalence of brain injury because of the delayed onset of symptoms and lack of standardization in the way it is recorded in healthcare records.


Responding to an overdose in a toxic drug supply (CATIE)


  1. Xavier C, Kuo M, Desai R, et al. Association between toxic drug events and encephalopathy in British Columbia, Canada: a cross-sectional analysis. Substance Abuse Treatment, Prevention, and Policy. 2023. 18:43. 10.1186/s13011-023-00544-z
  2. Brain Injury Canada. Opioid Overdose. Available from: https://braininjurycanada.ca/en/non-traumatic-brain-injury/opioid-overdose/
  3. Nanaimo Brain Injury Society. Acquired Brain Injury and Opioid Overdose Community Dialogue: Public Engagement Session Summary Report. Nanaimo, BC: Nanaimo Brain Injury Society; 2019. Available from: https://nbis.ca/opioid-overdose-dialogue/ 
  4. Voronkov M, Ataints J, Cocchairo B, et al. A vicious cycle of neuropathological, cognitive and behavioural sequelae of repeated opioid overdose. International Journal of Drug Policy. 2021 24 Jul; 97:103362. 10.1016/j.drugpo.2021.103362