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BACKGROUND. While preliminary evidence has begun to document intentional use of one substance to reduce the use of another, the phenomenon of drug substitution among people who use illicit opioids remains understudied. Therefore, we sought to estimate the prevalence and correlates of intentional substance use to reduce illicit opioid use among persons who use drugs (PWUD). METHODS. We analysed data from three prospective cohorts of PWUD in Vancouver, Canada, using multivariable generalized estimating equations (GEE). RESULTS. Between June 2012 and June 2016, 1527 participants were recruited and contributed 4991 interviews. Of those, 336 (22%) illicit opioid-using participants self-reported substitution to reduce illicit opioid use at least once during study period contributing 467 (9.4%) interviews. Among those interviews, substances substituted for opioids were alcohol (15 participants, 3.2%), stimulants (235, 50.3%), cannabis (129, 27.6%), benzodiazepines (21, 4.5%), and others (20, 4.3%). In multivariable GEE model adjusted for socio-demographic factors, reporting substitution to reduce illicit opioid use was positively associated with greater likelihood of daily cannabis use (Adjusted Odds Ratio = 1.56, 95% Confidence Interval: 1.24–1.96]. CONCLUSIONS. While daily cannabis use was associated with reporting opioid substitution attempts, additional study is needed to examine potential of cannabis/cannabinoids to reduce illicit opioid use.

Background:Post-traumatic stress disorder sharply increases the risk of depression and suicide. Individuals living with post-traumatic stress disorder frequently use cannabis to treat associated symptoms. We sought to investigate whether cannabis use modifies the association between post-traumatic stress disorder and experiencing a major depressive episode or suicidal ideation.Methods:We used data from the 2012 Canadian Community Health Survey-Mental Health, a nationally representative cross-sectional survey of non-institutionalized Canadians aged ⩾15 years. The relationship between post-traumatic stress disorder and each outcome was modelled using logistic regression with an interaction term for cannabis and post-traumatic stress disorder, controlling for demographic characteristics, mental health, and substance use comorbidities. The ratio of odds ratios and relative excess risk due to interaction was calculated to measure interaction on the multiplicative and additive scales, respectively.Results:Among 24,089 eligible respondents, 420 (1.7%) reported a current clinical diagnosis of post-traumatic stress disorder. In total, 106 (28.2%) people with post-traumatic stress disorder reported past-year cannabis use, compared to 11.2% of those without post-traumatic stress disorder ( p 0.05).Conclusions:This study provides preliminary epidemiological evidence that cannabis use may contribute to reducing the association between post-traumatic stress disorder and severe depressive and suicidal states. There is an emerging need for high-quality experimental investigation of the efficacy of cannabis/cannabinoids for the treatment of post-traumatic stress disorder.

Objectives. To characterize the prevalence and reasons for the use of cannabis as a strategy to reduce the harms arising from other substances. Methods. We drew data about recent cannabis use and intentions from 3 prospective cohort studies of marginalized people who use drugs based in Vancouver, Canada, from June 2016 to May 2018. The primary outcome was “use of cannabis for harm reduction,” defined as using cannabis for substitution for licit or illicit substances such as heroin or other opioids, cocaine, methamphetamine, or alcohol; treating withdrawal; or coming down off other drugs. Results. Approximately 1 in 4 participants reported using cannabis for harm reduction at least once during the study period. The most frequent reasons included substituting for stimulants (50%) and substituting for illicit opioids (31%). Conclusions. The use of cannabis for harm reduction is a common strategy among people who use drugs in our setting. Further research into the factors associated with this strategy is needed. Better characterization of the risks and benefits of substitution strategies, including for opioids and stimulants, may prompt new treatment options for PWUD.

Background The ongoing opioid overdose crisis is driven largely by exposure to illicitly-manufactured fentanyl. Preliminary observational and experimental research suggests that cannabis could potentially play a role in reducing use of prescription opioids among individuals with chronic pain. However, there is limited data on the effects of cannabis on illicit opioid consumption, particularly fentanyl, especially among individuals on opioid agonist therapy (OAT). We sought to assess the longitudinal association between cannabis use and exposure to fentanyl among people on OAT. Methods Data were drawn from two community-recruited prospective cohorts of people who use drugs in Vancouver, Canada. We used generalized linear mixed-effects modeling, adjusted by relevant confounders, to investigate the relationship between cannabis use and recent fentanyl exposure (both assessed by urine drug testing) among participants on OAT between 2016 and 2018. Results Among the 819 participants on OAT who contributed 1989 observations over the study period, fentanyl exposure was common. At the baseline interview, fentanyl was detected in a majority of participants (431, 53 %), with lower prevalence among individuals with urine drug tests positive for tetrahydrocannabinol (47 vs. 56 %, p = 0.028). Over all study interviews, cannabis use was independently associated with reduced likelihood of being recently exposed to fentanyl (Adjusted Prevalence Ratio = 0.91, 95 % Confidence Interval: 0.83 – 0.99). Conclusions Participants on OAT using cannabis had significantly lower risk of being exposed to fentanyl. Our findings reinforce the need for experimental trials to investigate the potential benefits and risks of controlled cannabinoid administration for people on OAT.

Objectives. To evaluate the impact of frequent cannabis use on injection cessation and injection relapse among people who inject drugs (PWID). Methods. Three prospective cohorts of PWID from Vancouver, Canada, provided the data for these analyses. We used extended Cox regression analysis with time-updated covariates to analyze the association between cannabis use and injection cessation and injection relapse. Results. Between 2005 and 2018, at-least-daily cannabis use was associated with swifter rates of injection cessation (adjusted hazard ratio [AHR] = 1.16; 95% confidence interval [CI] = 1.03, 1.30). A subanalysis revealed that this association was only significant for opioid injection cessation (AHR = 1.26; 95% CI = 1.12, 1.41). At-least-daily cannabis use was not significantly associated with injection relapse (AHR = 1.08; 95% CI = 0.95, 1.23). Conclusions. We observed that at-least-daily cannabis use was associated with a 16% increase in the hazard rate of injection cessation, and this effect was restricted to the cessation of injection opioids. This finding is encouraging given the uncertainty surrounding the impact of cannabis policies on PWID during the ongoing opioid overdose crisis in many settings in the United States and Canada.

Despite high rates of cannabis use during medication-based treatment of opioid use disorder (MOUD), uncertainty remains around how cannabis influences treatment outcomes. We sought to investigate the relationship between cannabis use during MOUD and a number of patient outcomes. We searched seven databases for original peer-reviewed studies documenting the relationship between cannabis use and at least one primary outcome (opioid use, treatment adherence, or treatment retention) among patients enrolled in methadone-, buprenorphine-, or naltrexone-based therapy for OUD. In total, 41 articles (including 23 methadone, 7 buprenorphine, 6 naltrexone, and 5 mixed modalities) were included in this review. For each primary outcome area, there was a small number of studies that produced findings suggestive of a supportive or detrimental role of concurrent cannabis use, but the majority of studies reported that cannabis use was not statistically significantly associated with the outcome. No studies of naltrexone treatment demonstrated significantly worse outcomes for cannabis users. We identified methodological shortcomings and future research priorities, including exploring the potential role of adjunct cannabis use for improving opioid craving and withdrawal during MOUD. While monitoring for cannabis use may help guide clinicians towards an improved treatment plan, cannabis use is unlikely to independently threaten treatment outcomes.

In an article in CMAJ , Fitzcharles and colleagues[1][1] raise a number of important concerns stemming from the need for more rigorous research into therapeutic applications of cannabinoids. Unfortunately, their arguments are undermined by their unsubstantiated claims about the relative risks of

BackgroundCannabis use is common among marginalized people who use illicit drugs (PWUD) but reasons for use remain poorly investigated. We sought to explore how different intentions for cannabis use relate to social, structural, and behavioural factors among PWUD in Vancouver, Canada.MethodsWe used data from cannabis-using participants in two community-recruited prospective cohort studies of PWUD. Using latent class analysis, we identified discrete cannabis-using groups based on self-reported intentions for use. Generalized estimating equations were used to examine correlates of class membership.ResultsBetween June 2016 and December 2018, 2,686 observations from 897 participants cannabis-using PWUD were analyzed. Four latent classes of cannabis use emerged: Class 1 (31.6%), characterized by non-medical purposes; Class 2 (37.5%), characterized by non-pain therapeutic use (e.g., stress, nausea/loss of appetite, and insomnia); characterized by Class 3 (21.9%) predominantly pain relief; and Class 4 (9.0%), characterized by a wide range of therapeutic uses in addition to pain management, including insomnia, stress, nausea/loss of appetite, and harm reduction. Class-specific structural, substance-, and health-related differences were observed, including indicators of better physical and mental health among the "recreational" class, despite evidence of more structural vulnerabilities (e.g., homelessness, incarceration).ConclusionsOur findings demonstrate a wide spectrum of motivations for cannabis use among PWUD. We observed important health-related differences between latent classes, demonstrating possible unmet healthcare needs among PWUD reporting therapeutic cannabis use. These findings inform ongoing policy surrounding access to cannabis for harm reduction purposes and applications of medical cannabis for PWUD.

Objectives Childhood trauma is common among street-involved youth and is associated with injection drug use. Illicit 3,4-Methylenedioxymethamphetamine (MDMA) use is also common among street-involved youth, and data suggest this substance has clinical utility in management of post-traumatic stress disorder (PTSD) and associated harms. Despite this, little is known about co-occurring patterns of MDMA use and injection drug use. Methods Data were derived from a prospective cohort of street-involved youth using illicit drugs in Vancouver, Canada. Using multivariable generalized estimating equation logistic regression, we examined the association between MDMA use and the use of injection drugs, adjusting for confounders such as polysubstance use and sociodemographic factors. Results 4941 surveys from 1208 participants between September 2005 and May 2015 were included. Of these, 829 (68.6%) were male, 815 (67.5%) reported white ethnicity, and median age was 21.7 years. Overall, 599 (49.6%) participants reported MDMA use, 544 (45.0%) reported injection drug use, and 244 (20.2%) reported concurrent MDMA and injection drug use at least once during the study period. In multivariable analyses, regular MDMA use was significantly negatively associated with injection drug use (Adjusted Odds Ratio [AOR] = 0.57, 95% CI: 0.46–0.69). Discussion After accounting for socio-demographic factors and polysubstance use, periods of reported regular MDMA use were negatively associated with reported injection drug use among this cohort. These findings suggest that, unlike the use of most other non-injection drugs, illicit MDMA use does not appear to promote injection drug use but rather is associated with a reduced likelihood of injection drug use.

Background and aims Cannabis use is common among people on opioid agonist treatment (OAT), causing concern for some care providers. However, there is limited and conflicting evidence on the impact of cannabis use on OAT outcomes. Given the critical role of retention in OAT in reducing opioid-related morbidity and mortality, we aimed to estimate the association of at least daily cannabis use on the likelihood of retention in treatment among people initiating OAT. As a secondary aim we tested the impacts of less frequent cannabis use. Design Data were drawn from two community-recruited prospective cohorts of people who use illicit drugs (PWUD). Participants were followed for a median of 81 months (interquartile range = 37-130). Setting Vancouver, Canada. Participants This study comprised a total of 820 PWUD (57.8% men, 59.4% of Caucasian ethnicity, 32.2% HIV-positive) initiating OAT between December 1996 and May 2016. The proportion of women was higher among HIV-negative participants, with no other significant differences. Measurements The primary outcome was retention in OAT, defined as remaining in OAT (methadone or buprenorphine/naloxone-based) for two consecutive 6-month follow-up periods. The primary explanatory variable was cannabis use (at least daily versus less than daily) during the same 6-month period. Confounders assessed included: socio-demographic characteristics, substance use patterns and social-structural exposures. Findings In adjusted analysis, at least daily cannabis use was positively associated with retention in OAT [adjusted odds ratio (aOR) = 1.21, 95% confidence interval (CI) = 1.04-1.41]. Our secondary analysis showed that compared with non-cannabis users, at least daily users had increased odds of retention in OAT (aOR = 1.20, 95% CI = 1.02-1.43), but not less than daily users (aOR = 1.00, 95% CI = 0.87-1.14). Conclusions Among people who use illicit drugs initiating opioid agonist treatment in Vancouver, at least daily cannabis use was associated with approximately 21% greater odds of retention in treatment compared with less than daily consumption.

Background Reforms to the legal status of medical and non-medical cannabis are underway in many jurisdictions, including Canada, as are renewed efforts to scale-up HIV treatment-as-prevention (TasP) initiatives. It has been suggested that high-intensity cannabis use may be associated with sub-optimal HIV treatment outcomes. Thus, using data from a setting with a community-wide treatment-as-prevention (TasP) initiative coinciding with increasing access to medical cannabis, we sought to investigate the possible impact of high-intensity cannabis use on HIV clinical outcomes. Methods Data was derived from the ACCESS study, a prospective cohort of HIV-positive people who use illicit drugs (PWUD) in Vancouver, Canada. Cohort data was confidentially linked to comprehensive clinical profiles, including records of all antiretroviral therapy (ART) dispensations and longitudinal plasma HIV-1 RNA viral load (VL) monitoring. We used generalized estimating equations (GEEs) to estimate the longitudinal bivariable and multivariable relationships between at least daily cannabis use and two key clinical outcomes: overall engagement in ART care, and achieving a non-detectable VL among ART-exposed participants. Results Between December 2005 and June 2015, 874 HIV-positive PWUD (304 [35%] non-male) were included in this study. In total, 788 (90%) were engaged in HIV care at least once over the study period, of whom 670 (85%) achieved non-detectable VL at least once. In multivariable analyses, ≥ daily cannabis use did not predict lower odds of ART care (Adjusted Odds Ratio [AOR]: 1.02, 95% confidence interval [CI]: 0.77–1.36) or VL non-detectability among ART-exposed (AOR: 0.96, 95% CI: 0.75–1.21). Upon testing for potential interactions, ≥ daily cannabis use was found to be negatively associated with ART engagement during periods of binge alcohol use ( p 0.05). Conclusion With the exception of frequent cannabis use during periods of binge alcohol use, our results showed no statistically significant impact of daily cannabis use on the likelihood of ART care or VL non-detectability among ART-exposed HIV-positive PWUD. These findings are reassuring in light of the impending legalization of cannabis in Canada and ongoing efforts to expand TasP initiatives.

Objectives Prescription opioid (PO) injection among people who use illicit drugs (PWUD) is an ongoing concern, yet little is known about drug use trajectories associated with initiating PO injection, including potential associations with heroin use. This study aimed to identify predictors of PO injection initiation among PWUD, and examine trends in heroin use before and after initiating PO injection. Methods Data were merged from three cohorts of PWUD recruited between September 2005 and November 2015. Predictors of PO injection initiation were identified using extended Cox regression models. Trends in heroin use pre- and post-initiation were examined with McNemar’s test and compared to matched controls with linear growth curve models. Results Among 1580 participants, 247 initiated PO injection yielding an incidence density of 3.9 (95% Confidence Interval [CI]: 3.4–4.4) per 100 person-years. In a multivariable analysis, independent predictors of PO injection initiation included heroin injection (Adjusted Hazard Ratio [AHR] = 4.39, 95% CI: 3.24–5.95) and non-injection PO use (AHR = 1.99, 95% CI: 1.25–3.17). In a sub-analysis, compared to matched controls, PO injection corresponded with elevated heroin use post-initiation ( p ≤ 0.05). Discussion In this study, heroin use and non-injection PO use strongly predicted PO injection initiation. Those who initiated PO injecting had elevated heroin use patterns post-initiation compared to controls. These findings suggest that transitioning to PO injection does not appear to be a substitute for heroin use among PWUD. These findings highlight the importance of addressing PO injection in harm reduction and treatment settings.

Background Ecological research suggests that increased access to cannabis may facilitate reductions in opioid use and harms, and medical cannabis patients describe the substitution of opioids with cannabis for pain management. However, there is a lack of research using individual-level data to explore this question. We aimed to investigate the longitudinal association between frequency of cannabis use and illicit opioid use among people who use drugs (PWUD) experiencing chronic pain. Methods and findings This study included data from people in 2 prospective cohorts of PWUD in Vancouver, Canada, who reported major or persistent pain from June 1, 2014, to December 1, 2017 (n = 1,152). We used descriptive statistics to examine reasons for cannabis use and a multivariable generalized linear mixed-effects model to estimate the relationship between daily (once or more per day) cannabis use and daily illicit opioid use. There were 424 (36.8%) women in the study, and the median age at baseline was 49.3 years (IQR 42.3–54.9). In total, 455 (40%) reported daily illicit opioid use, and 410 (36%) reported daily cannabis use during at least one 6-month follow-up period. The most commonly reported therapeutic reasons for cannabis use were pain (36%), sleep (35%), stress (31%), and nausea (30%). After adjusting for demographic characteristics, substance use, and health-related factors, daily cannabis use was associated with significantly lower odds of daily illicit opioid use (adjusted odds ratio 0.50, 95% CI 0.34–0.74, p < 0.001). Limitations of the study included self-reported measures of substance use and chronic pain, and a lack of data for cannabis preparations, dosages, and modes of administration. Conclusions We observed an independent negative association between frequent cannabis use and frequent illicit opioid use among PWUD with chronic pain. These findings provide longitudinal observational evidence that cannabis may serve as an adjunct to or substitute for illicit opioid use among PWUD with chronic pain., M-J Milloy and colleagues investigate use of cannabis and illicit opioids among people who use drugs reporting chronic pain., Author summary Why was this study done? High numbers of people who use (illicit) drugs (PWUD) experience chronic pain, and previous research shows that illicit use of opioids (e.g., heroin use, non-prescribed use of painkillers) is a common pain management strategy in this population. Previous research has suggested that some patients might substitute opioids (i.e., prescription painkillers) with cannabis (i.e., marijuana) to treat pain. Research into cannabis as a potential substitute for illicit opioids among PWUD is needed given the high risk of opioid overdose in this population. We conducted this study to understand if cannabis use is related to illicit opioid use among PWUD who report living with chronic pain in Vancouver, Canada, where cannabis is abundant and the rate of opioid overdose is at an all-time high. What did the researchers do and find? Using data from 2 large studies of PWUD in Vancouver, Canada, we analyzed information from 1,152 PWUD who were interviewed at least once and reported chronic pain at some point between June 2014 and December 2017. We used statistical modelling to estimate the odds of daily opioid use for (1) daily and (2) occasional users of cannabis relative to non-users of cannabis, holding other factors (e.g., sex, race, age, use of other drugs, pain severity) equal. For participants who reported cannabis use, we also analyzed their responses to a question about why they were using cannabis (e.g., for intoxication, for pain relief) We found that people who used cannabis every day had about 50% lower odds of using illicit opioids every day compared to cannabis non-users. People who reported occasional use of cannabis were not more or less likely than non-users to use illicit opioids on a daily basis. Daily cannabis users were more likely than occasional cannabis users to report a number of therapeutic uses of cannabis including for pain, nausea, and sleep. What do these findings mean? Although more experimental research (e.g., randomized controlled trial of cannabis coupled with low-dose opioids to treat chronic pain among PWUD) is needed, these findings suggest that some PWUD with pain might be using cannabis as a strategy to alleviate pain and/or reduce opioid use.

Issues Canada recently introduced a public health-based regulatory framework for non-medical cannabis. This review sought to identify a comprehensive set of indicators to evaluate the public health and safety impact of cannabis regulation in Canada, and to explore the ways in which these indicators may be expected to change in the era of legal non-medical cannabis. Approach Five scientific databases were searched to compile a list of cannabis-related issues of interest to public health and safety. A set of indicators was developed based on topics and themes that emerged. Preliminary evidence from other jurisdictions in the USA and Canada that have legalised medical and/or non-medical cannabis (e.g. Colorado, Washington) was summarised for each indicator, wherever possible. Key findings In total, 28 indicators were identified under five broad themes: public safety; cannabis use trends; other substance use trends; cardiovascular and respiratory health; and mental health and cognition. Preliminary trends from other legalised jurisdictions reveal little consensus regarding the effect of cannabis legalisation on public health and safety harms and an emerging body of evidence to support potential benefits (e.g. reductions in opioid use and overdose). Implications In addition to indicators of commonly discussed challenges (e.g. cannabis-related hospitalisations, cannabis-impaired driving), this review led to the recommendation of several indicators to monitor for possible public health and safety improvements. Conclusion In preparing a comprehensive public health and safety monitoring and evaluation system for cannabis regulation, this review underscores the importance of not only measuring the possible risks but also the potential benefits.

Prescription opioids (POs) are commonly prescribed to patients living with HIV/AIDS, while the illicit use of POs remains a major public health concern throughout Canada and the United States. We sought to identify the prevalence and correlates of PO injection among HIV-positive people who inject drugs (PWID) in Vancouver, Canada, where HIV/AIDS treatment and care is offered at no cost. We examined data from 634 individuals from an ongoing prospective cohort of HIV-positive PWID. Between December 2005 and November 2013, the median prevalence of recent PO injection was 24.2 % [interquartile range (IQR): 21.5–25.8 %]. In a multivariable generalized estimating equation model, Caucasian ethnicity, heroin injection, and drug dealing were positively associated with PO injection, while older age and methadone maintenance treatment were negatively associated with PO injection (all p < 0.05). Engagement on antiretroviral therapy was inversely associated with PO injection in a bivariable analysis, but did not remain significant after adjusting for heroin injection. These findings describe a particularly vulnerable sub-group of PWID who may benefit from targeted efforts to both minimize drug-related risk behaviors and support HIV/AIDS treatment.

Prescription opioid injection is a growing concern among people who use illicit drugs. Little is known about the potential health-related harms of injecting prescription opioids. Therefore, the authors undertook a systematic review to identify health outcomes associated with injecting prescription opioids. PubMed, Ovid MEDLINE®, EMBASE, Journals@Ovid, CINAHL, PsycInfo, Web of Science® Core Collection, CAB Direct, and ERIC databases were searched to identify English articles published between January 1990 and February 2015 that matched the inclusion criteria. Potentially relevant articles were those examining a clinical health outcome among people who use illicit drugs, in which a sub-group injects prescription opioids. The International Classification of Diseases (ICD-10) was used to clinically classify health outcomes. In total, 31 studies that met the inclusion criteria were identified and summarized. A modified version of the Downs and Black checklist was used to assess individual study quality and identify sources of bias. Findings supported associations between prescription opioid injection and hepatitis C infection, substance dependence and other mental health indicators, and lower general health. Associations with human immunodeficiency virus, overdose, and cutaneous infection were less consistent and varied according to prescription opioid type(s). Several potential sources of bias were identified as well as a need for more longitudinal research and more rigorous confounding adjustment. The current findings highlight a need to consider the growing popularity of prescription opioid injection in efforts to reduce drug-related harm among people who inject drugs.

A recent editorial in this journal provides a summary of key economic, social, and public health considerations of the forthcoming legislation to legalize, regulate, and restrict access to marijuana in Canada. As our government plans to implement an evidence-based public health framework for marijuana legalization, we reflect and expand on recent discussions of the public health implications of marijuana legalization, and offer additional points of consideration. We select two commonly cited public concerns of marijuana legalization – adolescent usage and impaired driving – and discuss how the underdeveloped and equivocal body of scientific literature surrounding these issues limits the ability to predict the effects of legalization. Finally, we discuss the potential for some potential public health benefits of marijuana legalization – specifically the potential for marijuana to be used as a substitute to opioids and other risky substance use – that have to date not received adequate attention.

Background Despite the popularity of 3,4-methylenedioxymethamphetamine (MDMA; ecstasy) among young people across North America and Europe, MDMA is rarely explored in studies of young people at high risk of injecting drugs. We conducted a study among street-involved youth who use illicit drugs in Vancouver, Canada, to understand if use of MDMA is associated with initiation of injection drugs. Methods We followed injection-naïve participants in the At-Risk Youth Study (ARYS), an ongoing prospective cohort of street-involved youth aged 14–26 who use illicit drugs. Bivariate and multivariate extended Cox models with time-updated variables were used to examine the association between MDMA use and initiation of injection drug use between September 2005 and May 2015. Results Among 483 youth, 306 (63.4%) had a history of MDMA use and 218 (45.1%) had used MDMA in the previous 6 months at baseline. A total of 105 (21.7%) youth initiated injection drug use over the 10-year period, yielding an incidence density of 8.51 (95% confidence interval [CI]: 6.96–10.30) per 100 person-years. MDMA use was not significantly associated with initiating injection drugs at the bivariate (hazard ratio: 0.93, 95% CI: 0.61–1.42) or multivariate (adjusted hazard ratio: 0.88, 95% CI: 0.57–1.35) level, after adjusting for socio-demographic and substance use confounders. Conclusions Amid ongoing frequent use of MDMA among some young people in North America, we did not observe an elevated risk of injection initiation among those who used MDMA in this cohort of street-involved youth.

Although abstinence from drug use is often a key goal of youth substance use treatment, transitioning to less harmful routes and types of drug use is desirable from both a clinical and public health perspective. Despite this, little is known about the trajectories of youth who inject drugs including changes in patterns of non-injection drug use. The At-Risk Youth Study (ARYS) is a longitudinal cohort of street-involved youth who use drugs in Vancouver, Canada. We used linear growth curve modeling to compare changes in non-injection drug use among participants who ceased injecting drugs for at least one 6-month period between September 2005 and May 2015 to matched controls who continued injecting over the same period. Of 387 eligible participants, 173 (44.7%) reported ceasing drug injection at least once. Non-injection drug use occurred during 160 (79.6%) periods of injection cessation. In adjusted linear growth curve analyses, the only non-injection drug use pattern observed to decrease significantly more than controls following injection cessation was daily crack/cocaine use (p = 0.024). With the exception of frequent crack/cocaine use, transitions out of injection drug use did not appear to coincide with increased reductions in patterns of non-injection drug use. Our findings indicate that most (80%) of the observed injection cessation events occurred in the context of ongoing substance use. Given that transitioning out of drug injection represents a significant reduction in risk and harm, efforts supporting vulnerable youth to move away from injecting may benefit from approaches that allow for ongoing non-injection drug use. &nbsp

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.