Thomas Kerr

Background: Methamphetamine use is on the rise among people who use opioids (PWUO), which brings additional complexity to the landscape of opioid agonist therapy (OAT). However, the circumstances surrounding methamphetamine use among PWUO and the role of OAT in this context remain under-explored. The overarching aims of this dissertation were to: 1) understandthe social context surrounding methamphetamine use among PWUO and 2) explore the interplaybetween methamphetamine use and OAT among PWUO.Methods: I first conducted a systematic review to synthesize the studies characterizing the trend of and factors associated with methamphetamine use among PWUO. Then, using empirical data obtained from two prospective cohorts of people who use drugs in Vancouver, Canada, between 2005 and 2020, I conducted multivariable generalized estimating equation (GEE) analyses to identify predictors of methamphetamine use initiation among individuals on OAT and examine the relationship between OAT engagement and methamphetamine use frequency among PWUO. Last, I employed repeated measures latent class analysis (RMLCA) to identify longitudinal substance use patterns among people receiving OAT, and used marginal structural Cox modelingto estimate their association with OAT discontinuation.Results: The systematic review found a wide range of individual, microsocial, and macrosocial factors associated with methamphetamine use among PWUO. The multivariable GEE analyses identified factors associated with methamphetamine initiation among individuals on OAT, including younger age, unstable housing, unprotected sex, previous methamphetamine use, recent cocaine use, and recent non-medical opioid use. Among PWUO, OAT engagement was associated with a lower methamphetamine use frequency in the absence of ongoing non-medical opioid use, while OAT initiation was associated with a greater methamphetamine use frequency. The RMLCA analysis identified four distinct substance use classes among people receiving OAT, with the opioid and stimulant use classes exhibiting a higher risk of OAT discontinuation.Conclusion: Addressing the ongoing overdose crisis requires comprehensive strategies encompassing prevention, intervention, and harm reduction efforts that consider both opioid and methamphetamine use. Care providers should adopt person-centred treatment approaches to meet the individualized needs of patients. Future research is needed to actively explore integrated treatment approaches and develop effective pharmaceutical interventions targeting concurrent opioid and methamphetamine use.

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Background: Canada and the United States are in the midst of an escalating overdose crisis. While poverty and socioeconomic disadvantage are increasingly recognized as important contributors to drug-related harm, their precise role in overdose remains understudied. This dissertation sought to: synthesize evidence regarding the pathways and mechanisms linking socioeconomic elements to overdose outcomes; examine the relationship between a comprehensive range of socioeconomic indicators and non-fatal overdose; identify and characterize gender-stratified profiles of socioeconomic exposures in men and women who use drugs; and, finally, determine whether these gender-stratified profiles predict non-fatal overdose. Methods: Data from Chapter 2 came from a realist review of research published between 2004 and 2019. Data for Chapters 3-5 cover the time period between 2014 and 2018 and are from two community-recruited prospective cohort studies of people who use drugs (PWUD) in Vancouver, Canada. A range of longitudinal analytic techniques were used, including: generalized linear mixed-effect models, repeated measures latent class analyses, and generalized estimating equations.Results: Findings from the realist review identified eight overlapping socioeconomic dimensions with documented linkages to overdose outcomes through material, normative, and bio-psychosocial pathways. In Chapter 3, across the total sample of PWUD from Vancouver, homelessness, lower material security, and participation in informal and illegal income generating activities were independently and positively associated with non-fatal overdose. In Chapter 4, gender-stratified analyses revealed that men and women experienced mutually reinforcing and overlapping socioeconomic exposures characterized by variations in income, material and housing security, participation in informal or illegal income generation, criminal justice involvement, and police contact. Gendered profiles of increasing socioeconomic disadvantage aligned with high-intensity drug use patterns (e.g., opioids and stimulants) and a range of health-related outcomes (e.g., HCV). In Chapter 5, exposure to multiple increasing dimensions of socioeconomic disadvantage was found to be independently associated with greater likelihood of experiencing non-fatal overdose in both men and women.Conclusions: Socioeconomic determinants are key drivers of overdose risk. To address the socioeconomic production of overdose risk, findings point to the urgent need to expand upstream and multilevel programs and policies, including inclusive, gender-informed health and social welfare programming, and broader drug policy reform.

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Background: Pain is a common concern among people who use drugs (PWUD), yet there remains a lack of research and evidence-based guidelines for managing pain in this population. As a result of inadequate pain management in the clinical setting, PWUD may self-manage pain in ways that pose high risk for morbidity and mortality, which is especially concerning in the context of the ongoing opioid overdose crisis in recent years. This research aims to fill current gaps in the literature by exploring the associations between pain, substance use and other health outcomes, risk behaviours, and clinical care.Methods: Quantitative data were derived between June 2014 to December 2018 from two community-recruited prospective cohort studies of PWUD in Vancouver, Canada. Data on pain were ascertained using the Brief Pain Inventory. A variety of longitudinal and cross-sectional analytic approaches were used to classify and examine the associations between pain and substance use, risk behaviours, sociodemographic and clinical characteristics, and ability to access health care services including addiction treatment.Results: A latent class analysis classified and compared observations among four subgroups of PWUD with pain: opioid agonist treatment (OAT) with low substance use, no OAT with low substance use, primarily daily heroin use (presumed heroin but may have contained fentanyl contamination), and primarily daily cocaine use. A generalized linear regression analysis found that greater pain-related functional interference was positively and independently associated with depressive symptoms as well as overdose and daily heroin use among PWUD. Additional multivariable regression analyses found that PWUD with greater pain severity were at higher risk of reporting barriers to accessing health services and inability to access addiction treatment. Conclusion: These findings highlight subgroups and specific risk factors, such as high-intensity heroin use and depressive symptoms, that may be associated with higher risk for morbidity or mortality related to pain and substance use among PWUD. These findings also identify a possible relationship between pain and ability to access health services, including addiction treatment, among PWUD. Altogether, this research provides evidence that may help to support more targeted, comprehensive, and accessible clinical services, policies and practices for PWUD with pain.

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Background: A growing body of evidence suggests that people with opioid use disorder (OUD) engage in polysubstance use (PSU). However, most studies are variable-centred and cross-sectional, and as a result, several aspects of longitudinal PSU patterns amongst people with OUD remain understudied. This thesis investigated longitudinal PSU classes among people with OUD by pursuing these specific objectives: systematically review the evidence on PSU classes among people with OUD; describe people with OUD’s substance use patterns after a national supply-level reduction intervention (i.e., reformulation of OxyContin); identify person-centred longitudinal patterns of PSU among them; and assess the longitudinal association between membership in different classes of PSU and non-fatal overdose events.Methods: To summarize the literature on PSU amongst people with OUD, a literature search was conducted following standard systematic review guidelines. Empirical data were obtained from three prospective cohorts of people who use drugs in Vancouver, Canada. Interrupted time-series (ITS) analysis was used to assess how people with OUD’s substance use patterns changed after the reformulation of OxyContin in Canada. Repeated measures latent class analysis (RMLCA) and longitudinal multivariable generalized estimating equations models were applied to identify distinct longitudinal classes of PSU and their associated odds of non-fatal overdose.Results: The systematic review identified 30 eligible studies and documented numerous PSU patterns among people with OUD and several methodological limitations in the literature. The ITS analysis showed that reducing access to OxyContin was not associated with reductions in illicit opioid use among people with OUD. The RMLCA analysis found five distinct longitudinal PSU patterns, including low/infrequent use, primarily opioid and methamphetamine use, primarily cannabis use, primarily opioid and crack use, and persistent PSU. Those in higher-intensity PSU classes were at higher odds of non-fatal overdose. Conclusion: This research underscored the heterogeneous nature of people with OUD in terms of both longitudinal substance use patterns and long-term odds for non-fatal overdose. It also highlighted the limited capacity of supply-level interventions in reducing opioid use among people with OUD. The high frequency of polysubstance use and heterogeneities among people with OUD should be reflected in OUD-related research, policy, and clinical practice developments.

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Background: The opioid overdose epidemic represents an unprecedented public health crisis in North America. Scientific evidence concerning long-term substance use trajectories and their impact on treatment outcomes among people who use drugs (PWUD) is critical to informing efforts designed to mitigate the harms of opioid dependency. This dissertation sought to: 1) identify factors promoting opioid use cessation among people receiving opioid agonist therapy (OAT); 2) characterize long-term injection drug use trajectories among PWUD; and 3) examine how pre- treatment opioid use patterns affect OAT outcomes as well as the impact of OAT on patterns of polysubstance use. Methods: Data for Chapter 2 came from a systematic review of research published between 1996 and 2019. Data for Chapters 3-5 were derived from three community-based prospective cohort studies of PWUD in Vancouver, Canada. Longitudinal analytical techniques were utilized, including: growth mixture model and multinomial logistic regression (Chapter 3); latent class growth analysis and generalized linear mixed-effects model (Chapter 4); and segmented regression (Chapter 5). Results: Findings from the systematic review demonstrated that among people receiving OAT, additional psychosocial interventions could help promote opioid cessation. In Chapter 3, five injection drug use trajectories were identified, ranging from persistent high-frequency use to early cessation. These trajectories were associated with baseline individual characteristics and drug use behaviours. In Chapter 4, two pre-treatment opioid use classes were identified (i.e., high frequency users and gradually increasing frequency users), which were related to subsequent treatment outcomes. In Chapter 5, a significant reduction in illicit opioid use was observed following OAT initiation. There was no significant difference comparing the pre-treatment and post-treatment trends for stimulants and cannabis. However, increasing problematic alcohol use was noted during the post-treatment period. Conclusion: There is a high level of heterogeneity in long-term substance use trajectories. The impact of treatment varies as a function of these substance use trajectories, individual characteristics, and the complex social and environmental contexts in which PWUD live. The findings reiterate the importance of developing long-term treatment strategies for people with substance use disorder and implementing services tailored to the needs of individuals characterized by distinct substance use trajectories.

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Background: A growing body of research has demonstrated the role of supervised drug consumption facilities (SCFs) in mitigating harms associated with illicit drug use. However, scientific evidence concerning long-term SCF utilization patterns and health impacts among people who use drugs (PWUD) is still lacking. Further, little is known about novel approaches to SCF programming, including peer involvement as staff, and how this may influence service dynamics. This dissertation sought to: systematically review the literature on the health and community impacts of SCFs; longitudinally examine discontinued use of a SCF; assess the impact of SCF use on all-cause mortality and exposure to violence; and characterize peer involvement in low-threshold SCFs, including how this may shape service engagement and associated health outcomes among PWUD.Methods: Quantitative data were derived from two community-recruited prospective cohort studies of PWUD in Vancouver, Canada. These data were confidentially linked to an external vital statistics database. In addition, observational fieldwork and interview data were drawn from a rapid ethnographic study examining the implementation, operations and impacts of low-threshold SCFs in Vancouver. Multivariable regression analyses of cohort data were used to examine the association between various factors and discontinued SCF use, as well as to longitudinally assess the impact of SCF use on all-cause mortality and exposure to violence. Ethnographic data were analyzed thematically to characterize peer involvement in SCFs. Results: Most SCF clients discontinued using this service during follow up, and injection cessation co-occurred with the majority of SCF use cessation events. Higher-risk subpopulations of PWUD were less likely to cease using the SCF while actively injecting. Frequent SCF use was protective against all-cause mortality, as well as exposure to violence among men but not women. Peer involvement in SCFs was found to promote service engagement and the reduction of harms among PWUD.Conclusions: These findings support the inclusion of SCFs within the continuum of services for PWUD, particularly given that use of such services may reduce the risk of serious harms, including mortality and exposure to violence. The expansion of peer-run and women-only SCFs may afford opportunities to extend the reach and impact of this intervention.

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Background: People who use illicit drugs (PWUD) experience a number of health-related harms that often lead to frequent hospitalizations. However, there exists little scientific evidence that has explored utilization and retention in hospital care, including leaving hospital against medical advice (AMA), among this population. The objective of this thesis is to provide evidence to improve hospital care for PWUD by first, identifying individual and contextual factors associated with leaving hospital AMA and other hospital-related experiences; and, second, to use these findings to develop and evaluate novel approaches to minimizing the risks and harms that PWUD experience in hospital settings. Methods: This dissertation draws on data collected from two open prospective cohort studies of HIV-positive and HIV-negative PWUD in Vancouver, Canada. These data were confidentially linked to a hospital discharge database as well as comprehensive records of HIV treatment and related clinical outcomes through a clinical monitoring laboratory. A variety of longitudinal and cross-sectional analytic techniques were used to examine the impact of intersecting individual and contextual factors on various hospital service outcomes. Results: This dissertation identified hospitals as a risk environment for PWUD, given the high prevalence of hospital discharge AMA and active illicit drug use in hospitals. The study findings highlighted various risk and protective factors for leaving hospital AMA, and discussed the negative consequences of being denied pain medication on illicit drug use in hospitals. The findings from this dissertation also point to novel strategies that may address these issues, including the implementation of an adult HIV/AIDS integrated health program operating in proximity to a hospital to minimize hospital discharge AMA among HIV-positive PWUD, as well as the potential for an in-hospital supervised injection facility (SIF) to reduce the harms associated with illicit drug use in hospital. Conclusion: Despite this setting of universal access to healthcare, there are individual- and contextual-level factors that play a pivotal role in shaping utilization and retention in hospital care among PWUD. The collective findings of this dissertation offer insights into how integrated harm reduction-based interventions may mitigate the risks associated with leaving hospital AMA and active illicit drug use in hospitals.

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Background: Globally, sex work is highly stigmatized, and the dominant policy approach has been criminalization and police enforcement. Despite a growing body of research on the social and structural determinants of violence, and sexual risk among sex workers, less is known about the specific features of these environments and the dynamic interplay that shape the negotiation of safety and sexual risk in sex transactions. Therefore, the objective of this dissertation is to examine how social and structural factors such as stigma, evolving sex work legislation and policing practices intersect to shape the working conditions of primarily street-based sex workers in Vancouver.Methods: This dissertation is based on in-depth qualitative interviews, focus groups and ethnographic fieldwork with street-based sex workers in Vancouver. Drawing on concepts of structural vulnerability and structural stigma, data analysis sought to characterize how evolving social and structural environments shape working conditions, health and safety among street-based sex workers. Results: The findings of this dissertation suggest that intersecting regimes of criminalization and stigmatization serve to perpetuate labour conditions that render sex workers at increased risk for violence and poor health, and further deny sex workers their citizenship rights to police protection and legal recourse. Despite police rhetoric of prioritizing the safety of sex workers, criminalization and policing strategies that target clients reproduce the harms created by the criminalization of sex workers, in particular, risks for violence and abuse. Despite the lack of formal legal and policy support for brothels in Canada, the environmental-structural supports afforded by unsanctioned, safer indoor sex work environments, in the context of supportive housing programs for women, promoted increased control over negotiating sex work transactions, including the capacity to refuse unwanted services, negotiate condom use, and avoid violent perpetrators.Conclusion: The collective work presented in this dissertation highlights the complex ways in which sex work related stigma, evolving sex work legislation, policing practices and sex work environments intersect to shape the working conditions of street-based sex workers, including citizenship and labour rights, violence, and ill health. The findings of this dissertation lend further support to calls for the full decriminalization of sex work.

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Background: In recent years, Thailand has intensified policing efforts as a strategy to address a continuing epidemic of illicit drug use. Thailand’s “war on drugs” campaign of 2003 received international criticism due to extensive human rights violations. However, few studies have since investigated the impacts of drug policing on people who inject drugs (IDU) in this setting. Drawing on the Risk Environment Framework, this dissertation sought to: explore IDUs’ lived experiences with police; identify the prevalence and correlates of experiencing beatings and drug testing by police; examine the relationship between exposures to policing and syringe sharing; and assess changes in the availability of illicit drugs among IDU in Bangkok, Thailand.Methods: Between June 2009 and June 2012, a community-recruited sample of IDU in Bangkok participated in a serial cross-­sectional mixed-­methods study and completed interviewer-­administered questionnaires and semi-structured in-­depth interviews. Audio-­recorded interviews were transcribed verbatim and a thematic analysis was conducted to document the character of IDUs’ encounters with police. A variety of multivariate regression techniques were used to estimate independent relationships between exposures to specific policing tactics and indicators of drug-­related harm, as well as to examine a temporal trend of street-­level availability of illicit drugs.Results: Respondents’ narratives indicated that drug policing involved numerous forms of human rights infringements and negatively influenced healthcare access among IDU in Bangkok. Reports of beatings and drug testing by police were common (38% and 67%, respectively) and were independently associated with various indicators of drug-­related harm, including syringe sharing and barriers to healthcare. Street-­level availability of illicit drugs increased significantly between 2009 and 2011.Conclusions: The findings indicate that the over-reliance on repressive drugpolicing is not suppressing the illegal drug market and is instead contributing to police-­perpetrated abuses, the perpetuation of risky injection behaviour, and an impediment to healthcare among IDU in Bangkok. These findings raise concern about the ongoing policing practices and point to the need for providing greater police oversight, as well as a shift toward more balanced approaches to drug control in this setting.

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In the public imagination, street youth are frequently defined through their relationships with place. Whether because they are viewed as innocent victims or violent criminals, young people who are homeless, destitute and visibly addicted to drugs are often understood to be out-of-place in the public spaces of city centers. This thesis is based on ethnographic fieldwork with a group of street-entrenched youth in Greater Vancouver conducted from January 2008 to January 2013. It included the creation of photography by youth exploring their sense of place in the city over time. Merging phenomenological perspectives on place-making with a focus on the processes of political economy and power that make some place worlds more enduring than others, I demonstrate that sense of place among youth who occupy the margins of urban space is far more complicated than conventional understandings imply. My findings reveal that, among youth, the “local” drug scene was produced in tension with a broader social spatial landscape of power, political economy and possibility, in which various remembered and imagined places were also implicated. In the context of this wider landscape-in-motion, involvement in Vancouver’s inner city drug scene could be articulated as both a sense of belonging and dislocation, “being in the center of something” and “getting lost in the city.” The drug scene could be a frontier of economic opportunity, in which anyone could attempt to stake a claim through activities like street-based drug dealing. And, it could be the site of a strictly enforced moral logic of violence and organized crime. The overarching objective of this thesis is to characterize these complex understandings, experiences and affects, and how they intersected with the regimes of living youth enacted on the streets. I conclude by highlighting that in order to meaningfully address youth’s initiation into and sustained involvement in “risky” forms of drug use and crime in settings like Vancouver, intervention at the level of policy is urgently needed in order to address social suffering across young people’s lives, and the wider geographies they implicate.

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Background: Growing awareness of the role social, structural, and environmental factors in producing harm among people who inject drugs (IDU) has underscored the need for safer environment interventions. However, emerging evidence underscores how current interventions are insufficient to bring about more significant reductions in drug-related harm. To date, there have been few studies examining how contextual forces operating within the wider risk environment shape the socio-spatial relations of IDU in relation to safer environment interventions and health care settings. This dissertation seeks to address this gap by examining the socio-spatial dynamics within three settings in Vancouver, Canada: the street-based drug scene; an ‘unsanctioned’ supervised drug consumption room (DCR); and, hospitals.Methods: This dissertation used an ethno-epidemiological approach, and the individual studies were undertaken in connection with ongoing prospective cohort studies of current and former drug users. Ethnographic fieldwork, including participant-observation, in-depth interviews and qualitative mapping exercises, sought to characterize the socio-spatial relations of IDU in relation to the abovementioned settings.Results: Study findings underscored how contextual forces shaped the socio-spatial relations of IDU, and thus access to and engagement with safer environment interventions and hospital settings. First, findings highlighted the role of gendered power relations within the street-based drug scene in shaping the spatial practices of highly vulnerable IDU, and constraining their access to a supervised injection facility. Second, findings demonstrated how, by permitting assisted injections, the DCR created a ‘legitimate place’ for IDU who require help injecting, and enabled them to enact risk reduction. Finally, social (e.g., stigmatization) and structural (e.g., abstinence-based drug policies) factors within hospital settings were found to produce considerable suffering (e.g., inadequate pain management) and contribute to discharges from hospital against medical advice.Conclusions: The collective findings of this dissertation demonstrate how the socio-spatial relations of IDU, and the contextual forces that impact upon them, are key determinants of drug-related harm and access to interventions and hospital services. These findings point to the need to modify and scale up existing safer environment interventions, and expand these into hospital settings, to mitigate the impacts of contextual forces on IDU and better address their health needs.

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Background: Given the limited understanding of the epidemiology of methamphetamine (MA) use among street-involved youth and injection drug users (IDU), this thesis sought to: systematically characterise the evidence base demonstrating associations between MA use and adverse health outcomes among young people; examine the incidence and predictors of MA injection initiation among a cohort of IDU in Vancouver; describe the prevalence and correlates of MA use among sexual minority drug users; determine whether frequent MA injection predicts emergency department (ED) utilisation; and finally, explore the pathways through which MA use drives injection-related risk behaviour including syringe sharing.Methods: Street-involved youth and IDU participating in three open prospective cohort studies were asked to complete semi-annual interviewer-administered questionnaires, provide blood samples for HIV testing, and consent to hospital database linkages. A variety of longitudinal techniques were used to investigate the association between self-reported MA-related outcomes (e.g., initiation, frequent use) and individual, social, and structural determinants of interest.Results: A systematic review identified consistent associations between MA use and a number of health outcomes, including depression, suicidal ideation, and psychosis. Scientific evidence to suggest an association between MA use and a number of previously suggested harms (e.g., infectious disease transmission, dental problems) is equivocal. Some subpopulations, including sexual minority drug users, are more likely to use MA, which appears to exacerbate exposure to HIV-related risks and other vulnerabilities. Longitudinal analysis revealed that young people, non-injection stimulant users, homeless individuals, and those involved in the city’s open drug scene are most likely to initiate MA injection. The injection of MA, particularly frequently, was associated with a number of health and behavioural outcomes, including an increased hazard of ED utilisation and syringe sharing. Barriers to accessing harm reduction and HIV prevention services likely account for many of these relationships. Conclusions: Methamphetamine use is increasingly common among street youth and IDU in Vancouver. Its use and resultant harms appear to be driven by intersecting individual, social, and structural factors. Comprehensive interventions that are based upon sound scientific evidence and that address existing health and social inequities among marginalised populations are required.

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Background: Given the limited contextual understanding of the HIV risk environment of survival sex workers in resource rich settings, the objectives of this thesis were: To explore the role of social and structural violence and gendered power relations in mediating women’s negotiation of HIV prevention; To examine the relationship between drug sharing with clients and the negotiation of sexual and drug transmission risk; To model the impact of early sexual abuse on subsequent HIV infection; To investigate the relationshipbetween environmental and structural factors and the negotiation of condom use with clients.Methods: Qualitative and quantitative data were drawn from a community-basedresearch project partnership in Vancouver, Canada. Women engaged in street-based sex work were invited through targeted peer outreach and time-space sampling to participate in interview-administered questionnaires, HIV screening, and social mapping. Additionally, women were purposively sampled to participate in focus group discussions about the contextual factors shaping HIV prevention.Results: Analysis of the narratives of sex workers revealed the paramount role ofsocial and structural violence in mediating women’s agency and access to resources and ability to practice HIV prevention. Drug sharing with clients was shown to be an important risk marker for elevated violence and unprotected sex. Early sexual abuse before 12 years was independently associated with HIV infection, and any sexual abuse before 18 years was associated with suicidalideations and generational vulnerability to sex work. Finally, structural andenvironmental barriers, including violence, displacement, and servicing clients inpublic spaces, were shown to elevate women’s sexual HIV risk through being pressured into unprotected sex by a client. Conclusions: The findings support the urgent need for social and environmental-structural HIV prevention efforts, in particular legal reforms, concomitantly with gender-sensitive harm reduction, that facilitate sex worker’sability to negotiate condom use in safer sex work environments.

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