UBC Theses and Dissertations
Cannabis use during an opioid-related public health crisis : implications for therapeutic advancements and harm reduction initiatives Lake, Stephanie Louise
Background: While opioid-related morbidity and mortality have risen in jurisdictions across North America, recent reforms to cannabis policy have sparked scientific inquiry into cannabinoid-based interventions to prevent or mitigate opioid-related harm. After systematically reviewing the literature on cannabis use during medication-based treatment of opioid use disorder (Chapter 2), this dissertation sought to: explore the role of cannabis in the relationship between methadone maintenance treatment (MMT) dose and treatment outcomes (Ch.3); characterize motivations for cannabis use (Ch.4); examine the association between cannabis use and illicit opioid use in the context of chronic pain (Ch.5); and document the impact of cumulative cannabis use on mortality (Ch.6) among marginalized people who use illicit drugs (PWUD). Methods: Data for Chapters 3-6 were derived from two community-based prospective cohort studies of PWUD in Vancouver, Canada. Regression analyses of longitudinal data were conducted, including generalized estimating equations (GEEs) and Cox frailty models for recurrent events (Ch.3); latent class analysis and GEEs (Ch.4); generalized linear mixed effects models (Ch.5); and time-varying Cox regression with weighted cumulative exposure measures modelled as restricted cubic splines (Ch.6). Results: In Chapter 3, frequent cannabis use significantly reduced the magnitude of the association between lower MMT dose and frequent illicit opioid use (n=1389), but not treatment retention (n=611). In Chapter 4, four latent classes of cannabis-using PWUD were identified, and links with socio-structural and health-related factors were observed, including poorer physical and mental health among therapeutic cannabis-using classes. In Chapter 5, high-frequency cannabis use was significantly negatively associated with high-frequency illicit opioid use among 1152 PWUD living with chronic pain. In Chapter 6, time to all-cause mortality was not impacted by increasing cumulative exposure to cannabis among 2211 PWUD. Conclusions: Certain motivations for cannabis use among PWUD are rooted in unmet healthcare needs and self-directed harm reduction. The findings of this dissertation signal the importance of conducting experimental research into cannabis for the management of opioid withdrawal and craving and as an opioid-sparing agent in the treatment of pain. In a newly legal environment, cannabis-based harm reduction efforts should be integrated alongside the provision of broader social and structural supports.
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