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Background: We sought to analyze the association between cannabis use to manage stimulant cravings and self-reported changes in stimulant use among structurally marginalized people who use unregulated drugs (PWUD)., Methods: The data for this secondary analysis was collected from a cross-sectional questionnaire administered to people who concurrently use cannabis and unregulated stimulants in Vancouver, Canada. We used logistic regression models to analyze the association between cannabis use to manage stimulant cravings and self-reported changes in the frequency of stimulant use., Results: In total, 297 individuals were included in the present study. Cannabis use to manage stimulant cravings was reported by 134 (45.1 %) participants and 104 (77.6 %) of these participants reported decreasing their stimulant use during periods of cannabis use. In the multivariable logistic regression analysis, cannabis use to manage stimulant cravings (adjusted Odds Ratio [aOR] = 0.24, 95 % confidence interval [CI]: 0.10, 0.56) was significantly associated with self-reported reductions in stimulant use. In the sub-analyses, cannabis use to manage stimulant cravings was significantly associated with reduced stimulant use among people who used crystal methamphetamine daily (aOR = 0.08, 95 % CI: 0.02-0.37) and was not significantly associated with reduced stimulant use among people who used crack/cocaine daily (aOR = 0.33, 95 % CI: 0.04-2.86)., Conclusions: These findings indicate that cannabis use to manage stimulant cravings is a common harm reduction strategy and suggest that this may be an effective strategy to reduce stimulant use among some PWUD., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

Background: While exposure to traumatic events and subsequent post-traumatic stress disorder (PTSD) are common among people who use drugs (PWUD), little is known about gender-based differences associated with PTSD in this population. We explore gender-based differences in factors associated with a probable PTSD diagnosis in a cohort of PWUD from Vancouver, Canada., Methods: Data were collected through the Vancouver Injection Drug Users Study (VIDUS) and the AIDS Care Cohort to Evaluate Exposure to Survival Services (ACCESS), two community-recruited cohorts of PWUD. Participants were administered the PTSD Checklist for DSM-5. Multivariable logistic regression was used to investigate social-structural factors and substance use patterns and behaviours associated with a probable PTSD diagnosis, stratified by self-identified gender. PTSD symptom clusters and brief descriptions of the worst traumatic event experienced were also reported., Results: Between December 2016 and December 2018, of 797 eligible participants, 295 (37.0%) identified as women. PTSD was more commonly reported in women compared to men (53.2% vs. 31.5%, p < 0.001). In multivariable analysis involving men, no correlates were associated with PTSD. In multivariable analysis involving women, PTSD was positively associated with exposure to violence (AOR: 3.66; 95%CI: 1.14-11.72), daily stimulant use (AOR: 2.32; 95%CI: 1.32-4.08) and heavy alcohol use (AOR: 3.84; 95%CI: 1.84-8.00), and negatively associated with being in a stable relationship (AOR: 0.46; 95%CI: 0.25-0.84)., Conclusions: Gender-based differences in PTSD diagnosis among a cohort of PWUD point to the need to develop gender-focused and trauma-informed health and social services to meet the immediate needs of PWUD living with PTSD., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Background: Opioid agonist therapy (OAT) models are generally provided without consideration of how pre-treatment characteristics may be associated with outcome. Therefore, we aimed to first characterize longitudinal trajectories of opioid use before initiating OAT. Then we explored the impact of OAT on opioid use across these pre-treatment trajectories., Methods: Data were derived from three prospective cohort studies involving people who use drugs in Vancouver, Canada. Latent class growth analysis was applied to identify opioid use trajectories based on individual-level observations three years before starting OAT. Multivariable generalized linear mixed model was used to examine whether engaging in OAT was associated with lower risk of illicit opioid use among participants with different pre-treatment opioid use trajectories., Results: 464 participants were included in the study between September 2005 and November 2018. Two pre-treatment opioid use trajectories were identified: high frequency users (246, 53.0%) and gradually increasing frequency users (218, 47.0%). We observed different strengths of association between OAT engagement and illicit opioid use among high frequency users (adjusted odds ratio [AOR] = 0.36, 95% Confidence Interval [CI]: 0.20 - 0.63) and gradually increasing frequency users (AOR = 0.91, 95% CI: 0.53 - 1.56). Unstable housing, any stimulant use, experiencing violence, drug dealing, sex work involvement, and incarceration were independently and positively associated with ongoing illicit opioid use., Conclusions: Distinct pre-treatment opioid use trajectories are likely to influence treatment outcomes. Research is required to determine if tailored strategies specific to people with different pre-treatment opioid use patterns have potential to improve outcomes of OAT., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Background: Despite the acute drug-related and behavioural risk factors for experiencing a drug overdose, few remote childhood experiences have been examined as risk factors for subsequent later life overdose risk. Parental heavy drinking has been associated with some later life negative outcomes, but little is known regarding the impact on drug overdoses, especially among people who inject drugs. Given the current overdose crisis in North America, we sought to evaluate the impact of parental heavy drinking on later life non-fatal overdose among people who inject drugs in Vancouver, Canada., Methods: Data were derived from two prospective cohort studies of community-recruited people who inject drugs in Vancouver between December 2012 and May 2016. We employed multivariable generalized estimating equations to examine the relationship between parental heavy drinking and non-fatal overdose in the past six months., Results: Among 327 eligible participants, 111 (33.9%) reported parental heavy drinking and 95 (29.1%) reported a non-fatal overdose at least once during the study period. In a multivariable analysis, experiencing parental heavy drinking remained independently associated with non-fatal overdose (adjusted odds ratio: 1.69; 95% confidence interval: 1.07-2.66) after adjustment for a range of socio-demographic and drug using confounders., Conclusions: These findings suggest long-term negative impacts of parental heavy drinking, on subsequent risk taking or other mechanisms associated with overdose. Current overdose prevention efforts may benefit from the evaluation of life course vulnerabilities that may be amenable to earlier interventions., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Background: No effective pharmacotherapies exist for the treatment of crack cocaine use disorders. Emerging data suggests that cannabinoids may play a role in reducing cocaine-related craving symptoms. This study investigated the intentional use of cannabis to reduce crack use among people who use illicit drugs (PWUD)., Methods: Data were drawn from three prospective cohorts of PWUD in Vancouver, Canada. Using data from participants reporting intentional cannabis use to control crack use, we used generalized linear mixed-effects modeling to estimate the independent effect of three pre-defined intentional cannabis use periods (i.e., before, during and after first reported intentional use to reduce crack use) on frequency of crack use., Results: Between 2012 and 2015, 122 participants reported using cannabis to reduce crack use, contributing a total of 620 observations. In adjusted analyses, compared to before periods, after periods were associated with reduced frequency of crack use (Adjusted Odds Ratio [AOR]=1.89, 95% Confidence Interval [CI]: 1.02-3.45), but not the intentional use periods (AOR=0.85, 95% CI: 0.51-1.41). Frequency of cannabis use in after periods was higher than in before periods (AOR=4.72, 95% CI: 2.47-8.99), and showed a tendency to lower frequency than in intentional cannabis use periods (AOR=0.56, 95% CI: 0.32-1.01)., Conclusions: A period of intentional cannabis use to reduce crack use was associated with decreased frequency of crack use in subsequent periods among PWUD. Further clinical research to assess the potential of cannabinoids for the treatment of crack use disorders is warranted., (Copyright © 2017. Published by Elsevier Ltd.)

Background: The evidence to date on whether HIV infection increases the risk of accidental drug overdose among people who inject drugs (PWID) is equivocal. Thus, we sought to estimate the effect of HIV infection on risk of non-fatal overdose among two parallel cohorts of HIV-positive and -negative PWID., Methods: Data were collected from a prospective cohort of PWID in Vancouver, Canada between 2006 and 2013. During biannual follow-up assessments, non-fatal overdose within the previous 6months was assessed. Bivariable and multivariable generalized mixed-effects regression models were used to determine the unadjusted and adjusted associations between HIV status, plasma HIV-1 RNA viral load, and likelihood of non-fatal overdose., Results: A total of 1760 eligible participants (67% male, median age=42, and 42% HIV-positive at baseline) were included. Among 15,070 unique observations, 649 (4.3%) included a report of a non-fatal overdose within the previous 6months (4.4% among seropositive and 4.3% among seronegative individuals). We did not observe a difference in the likelihood of overdose by HIV serostatus in crude (odds ratio [OR]: 1.05, p=0.853) analyses or analyses adjusted for known overdose risk factors (adjusted OR [AOR]: 1.19, p=0.474). In a secondary analysis, among HIV-positive PWID, we did not observe an association between having a detectable viral load and overdose (AOR: 1.03, p=0.862)., Conclusions: Despite the evidence that HIV infection is a risk factor for fatal overdose, we found no evidence for a relationship between HIV disease and non-fatal overdose. However, overdose remains high among PWID, indicating the need for ongoing policy addressing this problem, and research into understanding modifiable risk factors that predict non-fatal overdose., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Background: Though known to have abuse potential, benzodiazepine medications remain widely prescribed. Furthermore, issues related to benzodiazepine use by people who inject drugs (PWID) remain to be fully characterized. We therefore sought to examine the prevalence of and risk factors associated with benzodiazepine use in a street-involved urban population., Methods: Between May 1996 and November 2013, data were derived from two open prospective cohort studies in Vancouver, Canada, restricted to PWID. Multivariable logistic regression with generalized estimating equations (GEE) was used to determine factors independently associated with benzodiazepine use., Results: Over the study period, 2806 individuals were recruited, including 949 (34%) women. Of these, 1080 (38.5%) participants reported benzodiazepine use at least once during the study period. In the multivariable analysis, Caucasian ethnicity, ≥ daily heroin injection, ≥ daily cocaine injection, non-fatal overdose, incarceration, syringe sharing, and unsafe sex were all independently associated with benzodiazepine use. Conversely, older age, homelessness, and ≥ daily crack smoking were negatively associated with benzodiazepine use., Conclusions: Use of benzodiazepines was common in this urban setting and was associated with several markers of addiction severity and significant health and social vulnerabilities including syringe sharing and unsafe sex. These findings underscore the need to promote treatment for benzodiazepine use, safer benzodiazepine prescribing, including greater recognition of the limited indications for evidence-based use of this medication class., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Background: Despite barriers to its use in many settings, opioid agonist therapy with methadone has become the standard of care for treating opioid (e.g. heroin) use disorder. Since people with opioid use disorders have an increased incidence of incarceration, we undertook the present study to evaluate the association between incarceration and methadone maintenance therapy among a cohort of injection drug users in a Canadian setting., Methods: A cohort of people who inject drugs was prospectively followed between May 1996 and May 2013 in Vancouver, Canada. We investigated the relationship between recent incarceration and methadone use using multivariate generalized estimating equation (GEE) logistic regression analysis., Results: Overall, 2758 individuals were recruited during the study period and followed for a median of 64 (interquartile range: 23-106) months. After adjusting for various potential confounders in the multivariate GEE model, being incarcerated remained independently associated with a lower likelihood of having received methadone treatment (Adjusted Odds Ratio: 0.87, 95% confidence interval: 0.81-0.93)., Conclusions: Our study demonstrates that incarceration was independently associated with a significantly lower likelihood of being on methadone. Given the role of methadone in reducing the harms of heroin use, including drug acquisitive crime and recidivism, these data suggest a need to scale-up methadone provision for incarcerated injection drug users., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Introduction: Although people who inject drugs (IDU) remain at a high risk of accidental overdose, interventions that address overdose remain limited. Accordingly there is a continuing need to identify psychological and social factors that shape overdose risk. Despite being reported frequently among IDU, childhood trauma has received little attention as a potential risk factor for overdose. This study aims to evaluate relationships between non-fatal overdose and five forms of childhood maltreatment among a cohort of IDU in Vancouver, Canada., Methods: Data was obtained from two prospective cohorts of IDU between December 2005 and May 2013. Multivariate generalized estimating equations (GEEs) were used to explore relationships between five forms of childhood trauma and non-fatal overdose, adjusting for potential confounders., Results: During the study period, 1697 IDU, including 552 (32.5%) women, were followed up. At baseline, 1136 (67.0%) participants reported at least one form of childhood trauma, while 4-9% reported a non-fatal overdose at each semi-annual follow-up. In multivariate analyses, physical [adjusted odds ratio (AOR): 1.36, 95% confidence interval (CI): 1.08-1.71], sexual (AOR: 1.48, CI: 1.17-1.87), and emotional abuse (AOR: 1.54, CI: 1.22-1.93) and physical neglect (AOR: 1.28, CI: 1.01-1.62) were independently associated with non-fatal overdose (all p<0.05)., Conclusions: Childhood trauma was common among participants, and reporting an experience of trauma was positively associated with non-fatal overdose. These findings highlight the need to provide intensive overdose prevention to trauma survivors and to incorporate screening for childhood trauma into health and social programs tailored to IDU., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Background: Release from prison is associated with a markedly increased risk of both fatal and non-fatal drug overdose, yet the risk factors for overdose in recently released prisoners are poorly understood. The aim of this study was to identify risk and protective factors for non-fatal overdose (NFOD) among a cohort of illicit drug users in Vancouver, Canada, according to recent incarceration., Methods: Prospective cohort of 2515 community-recruited illicit drug users in Vancouver, Canada, followed from 1996 to 2010. We examined factors associated with NFOD in the past six months separately among those who did and did not also report incarceration in the last six months., Results: One third of participants (n=829, 33.0%) reported at least one recent NFOD. Among those recently incarcerated, risk factors independently and positively associated with NFOD included daily use of heroin, benzodiazepines, cocaine or methamphetamine, binge drug use, public injecting and previous NFOD. Older age, methadone maintenance treatment and HIV seropositivity were protective against NFOD. A similar set of risk factors was identified among those who had not been incarcerated recently., Conclusions: Among this cohort, and irrespective of recent incarceration, NFOD was associated with a range of modifiable risk factors including more frequent and riskier patterns of drug use. Not all ex-prisoners are at equal risk of overdose and there remains an urgent need to develop and implement evidence-based preventive interventions, targeting those with modifiable risk factors in this high risk group., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

We examined the impact of crystal methamphetamine injection on HIV RNA suppression among a prospective cohort of HIV-positive injection drug users initiating antiretroviral therapy. A multivariate Cox regression analysis found crystal methamphetamine injection to be negatively associated with viral load suppression (RH=0.63 [95% CI: 0.40-0.98]; p=0.039). This study is the first to our knowledge to demonstrate an association between crystal methamphetamine use and HIV RNA suppression., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

The delivery of antiretroviral therapy (ART) to injection drug users (IDU) may be influenced by provider concerns regarding the potential for increased HIV-related risk behavior following the initiation of HIV treatment. We evaluated whether ART initiation was associated with changes in syringe lending patterns among a long-term prospective cohort of HIV-positive IDU in Vancouver, Canada. Among 380 ART-naïve individuals eligible for this analysis, the median age was 34.2 (interquartile range [IQR] 27.7-40.8), 171 (45.0%) were female, and the median follow-up duration was 60 months (IQR=18-113). Between May 1996 and April 2008, 260 (68.4%) participants initiated ART. In a generalized linear mixed-effects model which compared each individual's likelihood of sharing syringes prior to and following the initiation of ART, syringe lending was not significantly associated with ART initiation in unadjusted (odds ratio=0.72, 95% CI: 0.38-1.36) or adjusted (odds ratio=0.78, 95% CI: 0.42-1.45) analyses. Concerns regarding increased injection risk behaviors following the initiation of ART were not observed in this setting., (Copyright © 2011 Elsevier Ltd. All rights reserved.)