Over the last decade, the unregulated drug supply in North America has become increasingly unpredictable and contaminated with illicitly-manufactured synthetic drugs resulting in more than 40,000 deaths in Canada between 2016 and 2023 (Special Advisory Committee on Toxic Drug Poisonings, 2024), and over 100,000 deaths in both 2021 and 2022 in the US (Spencer et al., 2023) from toxic drug poisoning. When the Canadian province of British Columbia (B.C.) declared a public health emergency in 2016 following a sudden rise in fatal drug poisonings, the primary concern was the emergence of fentanyl, a highly potent synthetic opioid (Ministry of Health, 2016). However, the unregulated drug supply is continuing to change rapidly, with additional contaminants emerging. While existing research has largely focused on how rising toxicity has impacted mortality rates, people who use drugs (PWUD) have raised concerns that the recent proliferation of benzodiazepines in the unregulated drug supply may be exacerbating their risk of violent victimization, particularly for women (Denis, 2021, Smyth, 2022; Speed at al., 2025).

Benzodiazepines, a class of drugs commonly prescribed for symptoms of anxiety and insomnia, have been increasingly detected in unregulated opioids in B.C. since around 2019 (Canadian Centre on Substance Use and Addiction, 2021; Laing et al., 2021; Russell et al., 2023; Scarfone et al., 2022). Many of the benzodiazepines detected are considered to be novel (i.e., illicitly manufactured, non-medically-approved sedatives in Canada or the US, such as etizolam or bromazolam, that can be several times stronger than their medically-approved counterparts; Russell et al., 2023). Post-mortem toxicology data from B.C.’s Coroners Service reports that detection of benzodiazepines in fatal overdose cases rose from 3 % in 2018–28 % in 2022 (B. C. Coroners Service, n.d.). Drug checking data in B.C. shows benzodiazepines were consistently found in about half of all expected-opioid samples by mid-2023 (BC Centre on Substance Use, 2023). When combined with opioids, benzodiazepines can increase risk of fatal and non-fatal drug poisoning (BC Centre on Substance Use, 2021). Symptoms of non-fatal drug poisoning from concurrent use of opioids and benzodiazepines include unconsciousness, extended periods of memory loss, and an inability to respond to external stimuli. The strong sedating effects of benzodiazepines may reduce the ability of people to respond if assaulted (BC Centre on Substance Use, 2021; Canadian Centre on Substance Use and Addiction, 2021). Notably, in some qualitative studies examining gendered experiences of the ongoing drug poisoning crisis, women reported that non-fatal overdose from fentanyl increases their risk of predatory or opportunistic physical and sexual violence (Boyd et al., 2018, Harris et al., 2021). In a recent qualitative study, women specifically described fear of unexpected benzodiazepine-related blackout or heightened intoxication exacerbating their vulnerability to violence (Speed et al., 2025).

Although the link between suspected exposure to benzodiazepines through contaminated drugs and interpersonal violence among PWUD remains underexplored, benzodiazepines have previously been implicated in producing vulnerability to violent victimization in research examining drug-facilitated sexual assaults (Morgillo et al., 2023, Navarro Escayola et al., 2023). Concerningly, PWUD, and disproportionately so women, already experience heightened rates of violence as a result of intersecting systems of structural violence, such as drug prohibition and related criminalization, capitalism-driven impoverishment, and patriarchy (Boyd et al., 2022, Fleming et al., 2023, McNeil et al., 2021; Perreault, 2020; Shannon et al., 2008). These oppressive systems force people who use unregulated drugs into over-policed and under-resourced environments that promote violence by perpetuating gender-based hierarchies and competition over limited resources. Although research shows PWUD use a variety of tactics to avoid violence, such as using alone (Collins et al., 2020, Ivsins et al., 2022), their ability to do so is also gendered (Marshall et al., 2008). For instance, women are more likely to be attacked by people they know and may not be able to avoid (Marshall et al., 2008). To our knowledge, there are no quantitative studies examining how increasing benzodiazepine contamination in the unregulated drug supply has impacted risk of violence among PWUD.

Therefore, we conducted a longitudinal, gender-based analysis of suspected exposure to benzodiazepines and experiences of physical and sexualized violence. Additionally, given that benzodiazepines are typically more common in the unregulated opioid supply and less so in unregulated stimulants (e.g., crystal methamphetamine, crack, and cocaine; Knill et al., 2023, Knill et al., 2022), the effect of benzodiazepines on risk for exposure to violence may differ depending upon whether people primarily use opioids or stimulants, or some combination of the two. As such, we analyzed whether associations between suspected exposure to benzodiazepines and experiences of violence were modified by different patterns of unregulated opioid and stimulant use.