Trajectories of injection drug use over 20 years (1988-2008) in Baltimore, Maryland

Structural and social changes due to the COVID-19 pandemic and their impact on engagement in substance use disorder treatment services: a qualitative study among people with a recent history of injection drug use in Baltimore, Maryland

BACKGROUND

Substance use disorder treatment and recovery support services are critical for achieving and maintaining recovery. There are limited data on how structural and social changes due to the COVID-19 pandemic impacted individual-level experiences with substance use disorder treatment-related services among community-based samples of people who inject drugs.

METHODS

People with a recent history of injection drug use who were enrolled in the community-based AIDS Linked to the IntraVenous Experience study in Baltimore, Maryland participated in a one-time, semi-structured interview between July 2021 and February 2022 about their experiences living through the COVID-19 pandemic (n = 28). An iterative inductive coding process was used to identify themes describing how structural and social changes due to the COVID-19 pandemic affected participants' experiences with substance use disorder treatment-related services.

RESULTS

The median age of participants was 54 years (range = 24-73); 10 (36%) participants were female, 16 (57%) were non-Hispanic Black, and 8 (29%) were living with HIV. We identified several structural and social changes due the pandemic that acted as barriers and facilitators to individual-level engagement in treatment with medications for opioid use disorder (MOUD) and recovery support services (e.g., support group meetings). New take-home methadone flexibility policies temporarily facilitated engagement in MOUD treatment, but other pre-existing rigid policies and practices (e.g., zero-tolerance) were counteracting barriers. Changes in the illicit drug market were both a facilitator and barrier to MOUD treatment. Decreased availability and pandemic-related adaptations to in-person services were a barrier to recovery support services. While telehealth expansion facilitated engagement in recovery support group meetings for some participants, other participants faced digital and technological barriers. These changes in service provision also led to diminished perceived quality of both virtual and in-person recovery support group meetings. However, a facilitator of recovery support was increased accessibility of individual service providers (e.g., counselors and Sponsors).

CONCLUSIONS

Structural and social changes across several socioecological levels created new barriers and facilitators of individual-level engagement in substance use disorder treatment-related services. Multilevel interventions are needed to improve access to and engagement in high-quality substance use disorder treatment and recovery support services among people who inject drugs.

Economic Evaluations of Establishing Opioid Overdose Prevention Centers in 12 North American Cities: A Systematic Review

OBJECTIVES

Overdose prevention centers (OPCs) provide a safe place where people can consume preobtained drugs under supervision so that a life-saving medical response can be provided quickly in the event of an overdose. OPCs are programs that are established in Canada and have recently become legally sanctioned in only a few United States jurisdictions.

METHODS

We conducted a systematic review that summarizes and identifies gaps of economic evidence on establishing OPCs in North America to guide future expansion of OPCs.

RESULTS

We included 16 final studies that were evaluated with the Consolidated Health Economic Evaluation Reporting Standards and Drummond checklists. Eight studies reported cost-effectiveness results (eg, cost per overdose avoided or cost per quality-adjusted life-year), with 6 also including cost-benefit; 5 reported only cost-benefit results, and 3 cost offsets. Health outcomes primarily included overdose mortality outcomes or HIV/hepatitis C virus infections averted. Most studies used mathematical modeling and projected OPC outcomes using the experience of a single facility in Vancouver, BC.

CONCLUSIONS

OPCs were found to be cost-saving or to have favorable cost-effectiveness or cost-benefit ratios across all studies. Future studies should incorporate the experience of OPCs established in various settings and use a greater diversity of modeling designs.

Longitudinal patterns of use of stimulants and opioids in the AIDS linked to the IntraVenous experience cohort, 2005-2019

BACKGROUND

Overdoses involving opioids and stimulants are on the rise, yet few studies have examined longitudinal trends in use of both substances. We sought to describe use and co-use of opioids and stimulants, 2005-2019, in the AIDS Linked to the Intravenous Experience (ALIVE) cohort - a community-based cohort of people with a history of injection drug use living in or near Baltimore, MD.

METHODS

We included 2083 ALIVE participants, who had at least two visits during the study period. Our outcome was based on self-reported use of opioids and stimulants in the prior 6 months. We estimated prevalence of 4 categories of use (neither stimulants nor opioids, only stimulants, only opioids, stimulants and opioids), using a non-parametric multi-state model, accounting for the competing event of death and weighting for informative loss to follow-up. All analyses were stratified by enrollment cohort, with the main analysis including participants who enrolled prior to 2015 and a sub-analysis including participants who enrolled 2015-2018.

RESULTS

In the main analysis, prevalence of using stimulants and opioids decreased from 38 % in 2005 to 12 % 2013 but stabilized from 2014 onwards (13-19 %). The prevalence of using only stimulants (7-11 %) and only opioids (5-10 %) was stable across time. Participants who reported using both were more likely to report homelessness, depression, and other substance use (e.g., marijuana and heavy alcohol use) than participants in the other use categories. On average, 65 % of visits with use of both were followed by a subsequent visit with use of both; of participants transitioning out of using both, 13% transitioned to using neither.

CONCLUSIONS

While use of stimulants and opioids declined in the cohort through 2013, a meaningful proportion of participants persistently used both. More research is needed to understand and develop strategies to mitigate harms associated with persistent use of both stimulants and opioids.

Association of current substance use treatment with future reduced methamphetamine use in an observational cohort of men who have sex with men in Los Angeles

INTRODUCTION

Methamphetamine use is highly prevalent among men who have sex with men (MSM), but knowledge of the long-term dynamics, and how they are affected by substance use treatment, is limited. This study aimed to describe trajectories of methamphetamine use among MSM, and to evaluate the impact of treatment for any kind of substance use on frequency of methamphetamine use.

METHODS

This analysis used data from a cohort of MSM in Los Angeles, CA, who participated in semi-annual study visits from 2014 to 2022. The study characterized trajectories of methamphetamine use using a continuous time multistate Markov model with three states. States were defined using self-reported frequency of methamphetamine use in the past six months: frequent (daily), occasional (weekly or less), and never. The model estimated the association between receiving treatment for any kind of substance use and changes in state of frequency of methamphetamine use.

RESULTS

This analysis included 2348 study visits among 285 individuals who were followed-up for an average of 4.4 years. Among participants who were in the frequent use state, 65 % (n = 26) of those who were receiving any kind of substance use treatment at a study visit had reduced their methamphetamine use at their next visit, compared to 33 % (n = 95) of those who were not receiving treatment. Controlling for age, race/ethnicity, and HIV-status, those who reported receiving current treatment for substance use were more likely to transition from occasional to no use (HR: 1.63, 95 % CI: 1.10-2.42) and frequent to occasional use (HR: 4.25, 95 % CI: 2.11-8.59) in comparison to those who did not report receiving current treatment for substance use.

CONCLUSIONS

Findings from this dynamic modeling study provide a new method for assessing longitudinal methamphetamine use outcomes and add important evidence outside of clinical trials that substance use treatment may reduce methamphetamine use.

Injection cessation and relapse to injection and the associated factors among people who inject drugs in Iran: The Rostam study

BACKGROUND

Drug injection is a major health-related problem worldwide. Injection cessation and relapse to injection could significantly alter the risk of HIV and hepatitis C virus (HCV) among people who inject drugs (PWID). This study aimed to estimate the rate of injection cessation and relapse to injection among PWID in Iran.

METHODS

This cohort study was conducted from 2018 to 2021 in the cities of Kerman and Tehran. Using a respondent-driven sampling (RDS) approach, 118 PWID with a history of injection in the last six months and negative HIV and HCV tests were recruited. Follow-up visits occurred every three months over a period of one year. Participants were interviewed and tested for HIV and HCV using rapid tests. Injection cessation was defined as the no injection of any type of drugs in the last three months. Relapse to injection was defined as re-initiating drug injection among those who had ceased injection. Two separate Cox regression models were applied, and an adjusted hazard ratio (aHR) with a 95% confidence interval (CI) were measured to assess the factors associated with each outcome.

RESULTS

The rate of injection cessation was 26.1 (95% CI: 21.3, 32.0) per 100 person-years, and the rate of relapse to injection was 32.7 (95% CI: 24.7, 43.2) per 100 person-years. At the baseline interview, 39.8% (n = 47) of participants reported injection cessation in the past three months before the interview. In the multivariable Cox regression analysis, the rate of relapse to injection was greater among women (aHR = 1.58; 95% CI: 1.01, 2.52), and those with higher monthly income (aHR = 1.63; 95% CI: 1.03, 2.59). However, there was no significant variable that predicted injection cessation.

CONCLUSION

Injection cessation was common among PWID in Iran, however, one-third relapsed to injection shortly after cessation. Harm reduction programs should include comprehensive strategies to reduce the probability of relapse among PWID who achieve injection cessation.

Trends in self-reported non-fatal overdose and patterns of substance use before and during the COVID-19 pandemic in a prospective cohort of adults who have injected drugs - Baltimore, Maryland, 2014-2022

BACKGROUND

Overdose deaths increased during the COVID-19 pandemic in the United States. Less is known about drug use behavior changes during the same time period. We examined differences in non-fatal overdose and drug use behaviors before and after the start of the COVID-19 pandemic in a community-recruited cohort of adults who have injected drugs.

METHODS

721 participants attended 7401 visits between Jan 2014 and Mar 2022. Outcomes (non-fatal overdose, drug route of administration, type of drugs used) were assessed via self-report in the last six months. We compared pre-pandemic (Jan 2014-Mar 2020) to inter-pandemic (Dec 2020-Mar 2022) prevalence of each outcome using Cohcrane-Maentel-Haeszel odds ratios (CMH-OR). We then estimated probabilities for transitioning between specific behaviors from participants' last pre-pandemic visit to their first inter-pandemic visit.

RESULTS

Comparing pre-pandemic visits to inter-pandemic visits, the prevalence of non-fatal overdose did not change (CMH-OR 1.06, 95% CI 0.75-1.50); the prevalence of injection (CMH-OR 0.13, 95% CI 0.1-0.17) and non-injection (CMH-OR 0.51, 95% CI 0.42-0.61) drug use declined. More than a third (35.7%) of persons using both injection and non-injection drugs pre-pandemic transitioned to exclusive non-injection use during the pandemic. By contrast, few (4.0%) persons using non-injection drugs exclusively pre-pandemic transitioned to injecting during the pandemic.

CONCLUSION

Among adults who have injected drugs, the start of the COVID-19 pandemic was associated with a reduced drug use prevalence and transitions from injection to non-injection use. Average overdose prevalence was unchanged, but these behavior changes may have helped mitigate overdose harm.

Trajectories of drug treatment and illicit opioid use in the AIDS Linked to the IntraVenous Experience cohort, 2014-2019

BACKGROUND

Medication for opioid use disorder (MOUD) is an effective intervention to combat opioid use disorder and overdose, yet there is limited understanding of engagement in treatment over time in the community, contextualized by ongoing substance use. We aimed to identify concurrent trajectories of methadone prescriptions, buprenorphine prescriptions, and illicit opioid use among older adults with a history of injection drug use.

METHODS

We used data on 887 participants from the AIDS Linked to the IntraVenous Experience cohort, who were engaged in the study in 2013 and attended ≥1 visit during follow-up (2014-2019). Outcomes were self-reported MOUD prescription and illicit opioid use in the last 6 months. To identify concurrent trajectories in all 3 outcomes, we used group-based multi-trajectory modeling. We examined participant characteristics, including sociodemographics, HIV status, and other substance use, overall and by cluster.

RESULTS

We identified 4 trajectory clusters: (1) no MOUD and no illicit opioid use (43%); (2) buprenorphine and some illicit opioid use (11%); (3) methadone and no illicit opioid use (28%); and (4) some methadone and illicit opioid use (18%). While prevalence of each outcome was stable across time, transitions on/off treatment or on/off illicit opioid use occurred, with the rate of transition varying by cluster. The rate of transition was highest in Cluster 3 (0.74/person-year) and lowest in Cluster 1 (0.18/person-year). We saw differences in participant characteristics by cluster, including that the buprenorphine cluster had the highest proportion of people with HIV and participants who identified as non-Hispanic Black.

CONCLUSIONS

Most participants had discontinued illicit opioid use and were also not accessing MOUD. Trajectories defined by engagement with buprenorphine or methadone had distinct sociodemographic and behavioral characteristics, indicating that tailored interventions to expand access to both types of treatment are likely needed to reduce harms associated with untreated opioid use disorder.

Health Outcomes by Neighborhood (HON): Effects of Neighborhood, Social Instability, and Health Factors on 12-Month Trajectories of Substance-Use Disorder Symptoms

BACKGROUND

Previous studies have shown that environment and health can influence drug use trajectories and the effects of substance use disorder (SUD) treatments. We hypothesized that trajectories of drug use-related problems, based on changes in DSM-5 symptoms, would vary by type(s) of drugs used, health factors, and neighborhood characteristics.

METHODS

We assessed mental and physical health, stress, social instability, neighborhood characteristics (disorderliness and home value), and DSM-5 symptom counts at two study visits, 12 months apart, in a community sample (baseline N = 735) in Baltimore, MD. Three prominent categories of drug-use trajectory were identified with K-means cluster analysis of symptom counts: Persistent (4 or more symptoms at both visits or at Visit 2), Improved (decrease from 4 or more symptoms at Visit 1 to 3 or fewer symptoms at Visit 2), and Low-Stable (3 or fewer symptoms at both visits). Baseline health and neighborhood measures were tested as predictors of trajectory in mediation and moderation models.

RESULTS

Among people with current opioid- and/or stimulant-use, odds of an Improved trajectory were (1) decreased with neighborhood disorder and social instability, or (2) increased with home value and social instability. Odds of a Low-Stable trajectory were decreased by social instability and stress but increased in those who were older or self-identified as white.

CONCLUSIONS

Trajectories of drug use-related problems are influenced by sociodemographic variables, neighborhood factors, and health. Assessing DSM-5 symptom counts as an outcome measure may be valuable in monitoring or predicting long-term trajectories and treatment effectiveness.

Trends in fatal and nonfatal overdose by race among people who inject drugs in Baltimore, Maryland from 1998 to 2019

OBJECTIVE

The objective of this study was to examine trends in fatal and nonfatal overdose in a community-based sample of current and former people who inject drugs (PWID).

METHODS

Data from 4826 current and former PWID from the AIDS Linked to the IntraVenous Experience (ALIVE) observational cohort study in Baltimore, Maryland, were used to characterize fatal and nonfatal overdose rates from 1998 to 2019. Poisson regression was used to examine factors associated with nonfatal overdose and differences by race among 1052 PWID between 2014 and 2019.

RESULTS

Fatal overdose rates reached a high of 13 per 1000 person-years in 2018. Among 1052 current and former PWID, of whom 75% were Black and one-third were female, the nonfatal overdose rate of 529 per 1000 person-years in 2019 was 8 times higher than 2014 (incidence rate ratio [IRR]=7.76, 95% CI: 3.35, 18.0). The annual adjusted increase in nonfatal overdose rate was 53% among Black PWID (IRR=1.53, 95% CI: 1.34, 1.75), compared to 14% among White PWID (IRR=1.14, 95% CI: 0.88, 1.46). Urban residence, opioid use, depressive symptoms, and hepatitis C infection were positively associated with nonfatal overdose among Black PWID. Recent injection drug use and tranquilizer use was associated with increased overdose among Black and White PWID.

CONCLUSIONS

Rates of fatal and nonfatal overdose were high and increased from 2014 to 2019 among current and former PWID, with the most dramatic increases in nonfatal overdose observed among Black PWID. These findings highlight the urgent need for additional resources to reduce the differential harms associated with opioids by race.

Is the relapse concept in studies of substance use disorders a 'one size fits all' concept? A systematic review of relapse operationalisations

ISSUES

Relapse is a theoretical construct and empirical object of inquiry. It is unclear how relapse is operationalised with regard to the various phases in substance use disorders (SUD). The aim was to investigate relapse operationalisations in SUDs studies after short- and long-term abstinence and remission, recovery and slip/lapse.

APPROACH

Systematic review using the following databases: Epistemonikos, Cochrane Central Register of Controlled Trials (CENTRAL and DARE), MEDLINE, EMBASE, Google Scholar, CINAHL, Web of Science and PsycINFO. Search returned 3426 articles, with 276 meeting the following inclusion criteria: empirical study published in English in a peer-reviewed journal; samples meet diagnostic criteria for dependence syndrome or moderate-severe drug use disorder or alcohol use disorder; reports relapse, abstinence, recovery, remission, slip or lapse. Review protocol registration: PROSPERO (CRD42020154062).

KEY FINDINGS

Thirty-two percent of the studies had no definition of 'relapse'. Most relapse operationalisations were defined according to measure (26%), time (17%), use (26%) and amount and frequency (27%). Of the 16 studies with a follow-up duration of up to 2 years, one (6%) contained a definition of 'long-term abstinence'. Of the 64 studies with a follow-up duration of more than 2 years, four (6%) contained a definition of 'long-term abstinence'. Of those, one (2%) mentioned 'early relapse' and one (2%) mentioned 'late relapse'.

IMPLICATIONS

Future research is needed to explore the possible difference between early and late relapse. Moreover, working to increase consensus on relapse operationalisations in SUD research is warranted.

CONCLUSIONS

We identified no consensus on relapse operationalisations nor agreement on the differentiation between early and late relapse. The clinical utility of current relapse operationalisations seems low and may compromise knowledge accumulation about relapse and implementation of research into treatment.

Assessing Drug Consumption Rooms and Longer Term (5 Year) Impacts on Community and Clients

BACKGROUND

Drug consumption rooms (DCRs) and supervised injecting facilities (SIFs) provide a safe environment in which people who inject drugs (PWIDs) can inject under hygienic and supervised conditions. Numerous reviews have documented the benefits of these facilities; however, there is a lack of clarity surrounding their long-term effects.

PURPOSE

To conduct, with a systematic approach, a literature review, of published peer-reviewed literature assessing the long-term impacts of DCRs/SIFs.

METHODS

A systematic search of the PubMed and Embase database was performed using the keywords: ("SUPERVISED" OR "SAFE*") AND ("CONSUMPTION" OR "INJECT*" OR "SHOOTING") AND ("FACILITY*" OR "ROOM*" OR "GALLERY*" OR "CENTRE*" OR "CENTER*" OR "SITE*"). Included studies were original articles reporting outcomes for five or more years and addressed at least one of the following client or community outcomes; (i) drug-related harms; (ii) access to substance use treatment and other health services; (iii) impact on local PWID population; (iv) impact on public drug use, drug-related crime and violence; and (v) local community attitudes to DCRs.

RESULTS

Four publications met our inclusion criteria, addressing four of the five outcomes. Long-term data suggested that while the health of PWID naturally declined over time, DCRs/SIFs helped reduce injecting-related harms. The studies showed that DCRs/SIFs facilitate drug treatment, access to health services and cessation of drug injecting. Local residents and business owners reported less public drug use and public syringe disposal following the opening of a DCR/SIF.

CONCLUSION

Long-term evidence on DCRs/SIFs is consistent with established short-term research demonstrating the benefits of these facilities. A relative paucity of studies was identified, with most evidence originating from Sydney and Vancouver. The overall body of evidence would be improved by future studies following outcomes over longer periods and being undertaken in a variety of jurisdictions and models of DCRs/SIFs.

Injecting frequency trajectories and hepatitis C virus acquisition: Findings from a cohort of people who inject drugs in Montréal, Canada

BACKGROUND

Frequent injecting increases hepatitis C (HCV) acquisition risk among people who inject drugs (PWID). However, few studies have examined how temporal fluctuations in injecting frequency may effect HCV infection risk. Thus, this study examined HCV incidence according to injecting frequency trajectories followed by PWID over one year in Montréal, Canada.

METHODS

At three-month intervals from March 2011 to June 2016, HCV-uninfected PWID (never infected or cleared infection) enrolled in the Hepatitis Cohort (HEPCO) completed interviewer-administered questionnaires and HCV testing. At each visit, participants reported the number of injecting days (0-30 days) for each of the past three months. In previous work, using group-based trajectory modeling, we identified five injecting frequency trajectories followed by participants over one year (months 1-12 of follow-up), including sporadic, infrequent, increasing, decreasing, and frequent injecting. In this study, we estimated group-specific HCV incidence (months 1-63 of follow-up) using posterior probabilities to assign participants to their most likely trajectory group.

RESULTS

Of 386 participants (mean age=40, 82% male, 48% never HCV-infected), 72 acquired HCV during 893 person-years of follow-up. HCV incidence for the whole study sample was 8.1 per 100 person-years (95%CI=6.4-10.1). Trajectory group-specific HCV incidences were highest for those injecting drugs with decreasing (23.9, 14.4-37.5) or increasing frequency (16.0, 10.1-24.3), intermediate for those injecting at consistently high frequency (10.2, 5.4-17.8), and lowest for those injecting infrequently (3.9, 2.2-6.5) or sporadically (4.3, 2.2-7.6).

CONCLUSION

Results suggest that PWID at highest HCV risk are those injecting at high frequency, either transitorily (increasing, decreasing injecting) or consistently (frequent injecting). This study highlights changes in injecting frequency as a potentially important dimension to consider among the factors leading to HCV acquisition. Clinical and public health interventions tailored to PWID with different injecting frequency profiles may contribute to HCV prevention.

Social and structural determinants of injecting-related bacterial and fungal infections among people who inject drugs: protocol for a mixed studies systematic review

INTRODUCTION

Injecting-related bacterial and fungal infections are a common complication among people who inject drugs (PWID), associated with significant morbidity and mortality. Invasive infections, including infective endocarditis, appear to be increasing in incidence. To date, preventive efforts have focused on modifying individual-level risk behaviours (eg, hand-washing and skin-cleaning) without much success in reducing the population-level impact of these infections. Learning from successes in HIV prevention, there may be great value in looking beyond individual-level risk behaviours to the social determinants of health. Specifically, the risk environment conceptual framework identifies how social, physical, economic and political environmental factors facilitate and constrain individual behaviour, and therefore influence health outcomes. Understanding the social and structural determinants of injecting-related bacterial and fungal infections could help to identify new targets for prevention efforts in the face of increasing incidence of severe disease.

METHODS AND ANALYSIS

This is a protocol for a systematic review. We will review studies of PWID and investigate associations between risk factors (both individual-level and social/structural-level) and the incidence of hospitalisation or death due to injecting-related bacterial infections (skin and soft-tissue infections, bacteraemia, infective endocarditis, osteomyelitis, septic arthritis, epidural abscess and others). We will include quantitative, qualitative and mixed methods studies. Using directed content analysis, we will code risk factors for these infection-related outcomes according to their contributions to the risk environment in type (social, physical, economic or political) and level (microenvironmental or macroenvironmental). We will also code and present risk factors at each stage in the process of drug acquisition, preparation, injection, superficial infection care, severe infection care or hospitalisation, and outcomes after infection or hospital discharge.

ETHICS AND DISSEMINATION

As an analysis of the published literature, no ethics approval is required. The findings will inform a research agenda to develop and implement social/structural interventions aimed at reducing the burden of disease.

PROSPERO REGISTRATION NUMBER

CRD42021231411.

The "black box" of treatment: Patients' perspective on what works in opioid maintenance treatment for opioid dependence

BACKGROUND

A lack of conceptual modeling of how the components of opioid maintenance treatment (OMT) for opioid dependence (OD) work causes it to occasionally be labeled the "black-box" of treatment. This study had a two-fold objective: First, to analyze which factors related to OMT for OD contribute to the abstinence of problematic use of non-prescribed opioids and sustain recovery, from the patients' perspective; second, to understand which changes OMT produced in the individuals' lives might significantly contribute to relapse prevention.

METHODS

We used qualitative methods of design, inquiry, and analysis from a convenience sample of 19 individuals in a Swedish treatment setting.

RESULTS

All the participants reported previous cycles of problematic use of non-prescribed opioids and other non-prescribed psychoactive substances, treatment, abstinence, recovery, and relapse before starting the current OMT program. During the pre-treatment stage, specific events, internal processes, and social environments enhanced motivation toward abstinence and seeking treatment. During the treatment stage, participants perceived the quality of the human relationships established with primary social groups as important as medication and the individual plan of care in sustaining recovery. From the participants' perspective, OMT was a turning point in their life course, allowing them a sense of self-fulfillment and the reconstruction of personal and social identity. However, they still struggled with the stigmatization produced by a society that values abstinence-oriented over medication-assisted treatments.

CONCLUSION

OMT is not an isolated event in individuals' lives but rather a process occurring within a specific social context. Structural factors and the sense of acceptance and belonging are essential in supporting the transformation. Treatment achievements and the risk for relapse vary over time, so the objectives of the treatment plan must account for characteristics of the pre-treatment stage and the availability and capacity of individuals to restructure their social network, besides the opioid maintenance treatment and institutional social care.

Socioeconomic stability is associated with lower injection frequency among people with distinct trajectories of injection drug use

BACKGROUND

Little is known about how socioeconomic circumstances relate to injection frequencies among people who inject drugs (PWID) with diverse trajectories of injection. We aimed to characterize trajectories of injection drug use in a community-based sample of PWID over 7.5 years and to investigate the extent to which two modifiable factors reflecting socioeconomic stability-stable housing and stable income-relate to injection frequencies across distinct trajectories.

METHODS

HEPCO is an open, prospective cohort study of PWID living in Montréal with repeated follow-up at three-month or one-year intervals. Self-reported data on injection frequency, housing and income are collected at each visit. Injection frequency was defined as the number of injection days (0-30), reported for each of the past three months. Using group-based trajectory modeling, we first estimated average trajectories of injection frequency. Then, we estimated the trajectory group-specific average shift upward or downward associated with periods of stable housing and stable income relative to periods when these conditions were unstable.

RESULTS

Based on 19,527 injection frequency observations accrued by 529 participants followed over 2011-2019 (18.3% female, median age: 41), we identified five trajectories of injection frequency: three characterized by sustained injection at different frequencies (28% infrequent; 19% fluctuating; 19% frequent), one by a gradual decline (12%), and another by cessation (28%). Periods of stable housing and stable income were each independently associated with a lower injection frequency, on average, in all five trajectory groups (2.2-7.5 fewer injection days/month, depending on the factor and trajectory group).

CONCLUSION

Trajectories of injection drug use frequency were diverse and long-lasting for many PWID. Despite this diversity, socioeconomic stability was consistently associated with a lower injection frequency, emphasizing the close relationship between access to fundamental necessities and injection patterns in all PWID, irrespective of whether they are on a path to cessation or sustained injecting.

Migration Patterns from an Open Illicit Drug Scene and Emergency Department Visits among People Who Use Illicit Drugs in Vancouver, Canada

BACKGROUND

People who use illicit drugs (PWUD) experience various adverse health outcomes leading to increased healthcare service utilization. PWUD are also a highly mobile population which poses challenges to healthcare delivery. The objective of this study was to identify migration patterns from the Downtown Eastside (DTES), an urban illicit drug scene in Vancouver and to estimate the impact of different migration patterns on two outcomes: a) emergency department (ED) visits and b) ED visits resulting in inpatient admission among PWUD.

METHODS

Three prospective cohorts of PWUD in Vancouver were linked with regional ED data. We defined the optimal number of trajectory groups that best represented distinct patterns of migration from Vancouver's DTES using a latent class growth analysis. Then, generalized estimating equations were used to estimate the effect of migration patterns on the two ED outcomes.

RESULTS

Four distinct migration trajectory patterns were identified among the 1210 included participants: PWUD who consistently lived in the DTES, those who migrated out of DTES early, those who migrated out of DTES late, and those who frequently revisited the DTES. Participants who frequently revisited the DTES had higher odds of an ED visit (adjusted odds ratio = 1.62; 95% confidence interval: 1.28-2.06). There was no significant association between migration patterns and inpatient admission.

CONCLUSIONS

We found that PWUD who frequently revisited the DTES were more likely to have utilized the ED, suggesting that there may be a subgroup of PWUD who are at increased risk of experiencing negative health outcomes.Supplemental data for this article is available online at 10.1080/10826084.2021.1958849.

Long term pre-treatment opioid use trajectories in relation to opioid agonist therapy outcomes among people who use drugs in a Canadian setting

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.

Beyond abstinence and relapse: cluster analysis of drug-use patterns during treatment as an outcome measure for clinical trials

RATIONALE

Many people being treated for opioid use disorder continue to use drugs during treatment. This use occurs in patterns that rarely conform to well-defined cycles of abstinence and relapse. Systematic identification and evaluation of these patterns could enhance analysis of clinical trials and provide insight into drug use.

OBJECTIVES

To evaluate such an approach, we analyzed patterns of opioid and cocaine use from three randomized clinical trials of contingency management in methadone-treated participants.

METHODS

Sequences of drug test results were analyzed with unsupervised machine-learning techniques, including hierarchical clustering of categorical results (i.e., whether any samples were positive during each week) and K-means longitudinal clustering of quantitative results (i.e., the proportion positive each week). The sensitivity of cluster membership as an experimental outcome was assessed based on the effects of contingency management. External validation of clusters was based on drug craving and other symptoms of substance use disorder.

RESULTS

In each clinical trial, we identified four clusters of use patterns, which can be described as opioid use, cocaine use, dual use (opioid and cocaine), and partial/complete abstinence. Different clustering techniques produced substantially similar classifications of individual participants, with strong above-chance agreement. Contingency management increased membership in clusters with lower levels of drug use and fewer symptoms of substance use disorder.

CONCLUSIONS

Cluster analysis provides person-level output that is more interpretable and actionable than traditional outcome measures, providing a concrete answer to the question of what clinicians can tell patients about the success rates of new treatments.

Impact of migration from an illicit drug scene on hospital outcomes among people who use illicit drugs in Vancouver, Canada

INTRODUCTION AND AIMS

People who use illicit drugs (PWUD) are vulnerable to an array of negative health outcomes, and increased hospital services utilisation. PWUD are also a transient population which poses challenges to the provision of optimal health care. The objective of this study was to identify out-migration patterns from Vancouver's Downtown Eastside (DTES), a neighbourhood where services for PWUD are concentrated, and to estimate the impact of these patterns on hospitalisation events among PWUD.

DESIGN AND METHODS

Data were collected through three prospective cohorts of PWUD in Vancouver, which were linked with health administrative data. Latent class growth analysis was used to define migration trajectory groups. Poisson regression was used to estimate the effect of migration patterns on hospitalisation events.

RESULTS

A total of 1180 participants were included in the study. Four latent classes were identified: early migration out (243, 20.6%); frequent revisit (112, 9.5%); late migration out (219, 18.6%); and consistently living in the DTES (606, 51.4%). Compared with those who consistently lived in the DTES, participants in the early migration out group had lower hospitalisation events (adjusted rate ratio = 0.65; 95% confidence interval: 0.48-0.90).

DISCUSSION AND CONCLUSION

We found that PWUD who migrated out of the DTES early had lower hospitalisation events compared to those who consistently lived in the DTES, which may be a function of lesser addiction severity among this trajectory group. These findings underscore a need to provide transitional health and social service supports for other trajectory groups in an effort to minimise hospitalisation for preventable causes.

Patterns of Drug and Alcohol Use and Injection Equipment Sharing Among People With Recent Injecting Drug Use or Receiving Opioid Agonist Treatment During and Following Hepatitis C Virus Treatment With Direct-acting Antiviral Therapies: An International Study

BACKGROUND

In many settings, recent or prior injection drug use remains a barrier to accessing direct-acting antiviral treatment (DAA) for hepatitis C virus (HCV) infection. We examined patterns of drug and alcohol use and injection equipment sharing among people with recent injecting drug use or receiving opioid agonist treatment (OAT) during and following DAA-based treatment.

METHODS

SIMPLIFY and D3FEAT are phase 4 trials evaluating the efficacy of DAA among people with past 6-month injecting drug use or receiving OAT through a network of 25 international sites. Enrolled in 2016-2017, participants received sofosbuvir/velpatasvir (SIMPLIFY) or paritaprevir/ritonavir/dasabuvir/ombitasvir ± ribavirin (D3FEAT) for 12 weeks and completed behavioral questionnaires before, during, and up to 2 years posttreatment. The impact of time in HCV treatment and follow-up on longitudinally measured longitudinally measured behaviors was estimated using generalized estimating equations.

RESULTS

At screening, of 190 participants (mean age, 47 years; 74% male), 62% reported any past-month injecting 16% past-month injection equipment sharing, and 61% current OAT. Median alcohol use was 2 (Alcohol Use Disorders Identification Test-Consumption; range, 1-12). During follow-up, opioid injecting (odds ratio [OR], 0.95; 95% confidence interval [CI], 0.92-0.99) and sharing (OR, 0.87; 95% CI, 0.80-0.94) decreased, whereas no significant changes were observed for stimulant injecting (OR, 0.98; 95% CI, 0.94-1.02) or alcohol use (OR, 0.99; 95% CI, 0.95-1.04).

CONCLUSIONS

Injecting drug use and risk behaviors remained stable or decreased following DAA-based HCV treatment. Findings further support expanding HCV treatment to all, irrespective of injection drug use.

CLINICAL TRIALS REGISTRATION

SIMPLIFY, NCT02336139; D3FEAT, NCT02498015.

Trajectories of heroin use predict relapse risk among heroin-dependent patients: A 5-year follow-up study

OBJECTIVES

The relationship between past drug use trajectory and long-term relapse risk after rehabilitation among heroin-dependent patients remain understudied. The primary objectives were to identify longitudinal heroin use patterns of heroin-dependent patients, to determine the associative factors with trajectories and to investigate the impact of trajectory groups on relapse after finishing compulsory rehabilitation programs.

MATERIALS AND METHODS

A total of 564 heroin-dependent patients were recruited from 4 compulsory rehabilitation facilities in Shanghai, China between 2007 and 2008. The baseline data was linked to participants' follow-up data on relapse from official records. Group-based trajectory model was used to identify distinctive drug use trajectory groups. The association between the identified group and heroin relapse risk was then analyzed to understand the role of past drug use trajectory on relapse.

RESULTS

Five trajectory groups were identified in this cohort: (1) Rapid Decrease (9.9%); (2) Persistent High (32.0%); (3) Slow Decrease (34.1%); (4) Gradual Increase (4.5%); (5) Persistent Low (19.5%). Gender, age, education, and impulsivity were found to be different between the five groups. During the 5 years after discharged from the compulsory program, 291 (59.0%) individuals relapsed. Multivariate logistic regression analysis showed that the persistent high group (OR: 2.77 [1.46-5.24]), slow decrease group (OR: 2.31 [1.32-4.06]) and gradual increase group (OR: 3.50 [1.18-10.39]) was positively associated with the heroin relapse risk when compared to the persistent low group.

CONCLUSIONS

Heroin use trajectories vary among heroin-dependent patients in China. The trajectories of heroin use before compulsory rehabilitation are associated with subsequent long-term relapse risk.

Characterizing latent classes of social support among persons who inject drugs

BACKGROUND

Social network members influence risk and health behaviors, yet little is known about the support that persons who inject drugs (PWID) receive from their closest ties.

METHODS

970 participants from the AIDS Linked to the IntraVenous Experience (ALIVE) study completed a social network survey between April 2016 and June 2017 about their five closest ties. Our analysis: 1) identified latent classes of support received by participants; 2) determined whether class membership differed by current (≤12 months) vs. former (>12 months) injection drug use; 3) compared classes of support by individual and network characteristics.

RESULTS

970 participants listed 3,388 network members. We identified three support classes: (1) Moderate (n = 249): probabilities of support <0.40; (2) High (n = 366): probabilities of support 0.58-0.82; (3) Very high (n = 355): probabilities of support 0.91-0.99. In adjusted analysis compared to moderate support, the odds of high and very high support increased as the mean age of network members increased (Adjusted Odds Ratio [AOR]:1.03; 95 % CI: 1.01, 1.05) and as the number of network members with whom they interacted daily increased (AOR-high: 1.33; 95 % CI:1.14, 1.56 and AOR-very high: 1.54; 95 % CI: 1.30, 1.83). While current injection drug use was associated with lower unadjusted odds of high and very high support, the associations were not statistically significant in adjusted analysis.

CONCLUSIONS

Support was higher among networks of older ties and more frequent interaction, but differences did not appear to be driven by injection drug use status. Findings point to the importance of the closest social ties.

Associations between housing stability and injecting frequency fluctuations: findings from a cohort of people who inject drugs in Montréal, Canada

BACKGROUND

The relationship between housing stability and drug injecting is complex, as both outcomes fluctuate over time. The objectives were to identify short-term trajectories of housing stability and injecting frequency among people who inject drugs (PWID) and examine how patterns of injecting frequency relate to those of housing stability.

METHODS

At three-month intervals, PWID enrolled between 2011 and 2016 in the Hepatitis Cohort completed an interviewer-administered questionnaire and were tested for hepatitis C and HIV infections. At each visit, participants reported, for each of the past three months, the accommodation they lived in the longest (stable/unstable) and the number of injecting days (0-30). Group-based dual trajectory modeling was conducted to identify housing stability and injecting frequency trajectories evolving concomitantly over 12 months and estimate the probabilities of following injecting trajectories conditional upon housing trajectories.

RESULTS

386 participants were included (mean age 40.0, 82 % male). Three housing stability trajectories were identified: sustained (53 %), declining (20 %), and improving (27 %). Five injecting frequency trajectories were identified: sporadic (26 %), infrequent (34 %), increasing (15 %), decreasing (11 %), and frequent (13 %). PWID with improving housing were less likely to increase injecting (8 %) compared to those with sustained (17 %) or declining housing (17 %).

CONCLUSIONS

Improving housing was associated with a lower probability of increasing injecting compared to declining housing, while sustained housing stability was associated with a higher probability of increasing injecting compared to improving housing. Therefore, policies to improve PWID's access to stable housing are warranted and may reduce, to some extent, drug injecting and related harms.

Estimating the size of crack cocaine users in France: Methods for an elusive population with high heterogeneity

BACKGROUND

Despite several sources corroborating an expanding market and increased visibility and greater diversity in users' profiles, very little is known about the number of crack cocaine users in France.

METHOD

The estimates rely on a single data source capture-recapture method. Annual data are extracted from treatment centres nationwide. To account for heterogeneity, we use an innovative zero-truncated geometric, regression-based estimator controlling for individual and centre characteristics. We use the well-known Zelterman estimator as a benchmark.

RESULTS

The number of crack cocaine users received in treatment centres increased dramatically, from 3388 in 2010 to 5143 in 2017 (+52%). The estimated number of crack cocaine users is believed to have tripled over the course of the same period (from 9775, 95% CI [8288-11530] to 28983 [24876-33766], respectively), with prevalences below 1‰, similar to other European countries. The coverage rate (observed number/estimated number of users) decreased in a similar fashion, indicating lower utilization. In particular, females and younger users are underestimated by data from treatment centres.

CONCLUSION

The prevalence of crack cocaine use is fairly low but steadily increasing. The diversity in users' profiles is a challenge to prevention and public health policies that should expand their scope to a more inclusive perspective of what defines crack cocaine users. Our method overcomes several methodological issues (data sources, data linkage, heterogeneity) and can be easily applied to a wide range of settings.

Trajectories of injection drug use among people who use drugs in Vancouver, Canada, 1996-2017: growth mixture modeling using data from prospective cohort studies

BACKGROUND AND AIMS

Injection drug use patterns are known to change over time, although such long-term changes have not been well described. We sought to characterize longitudinal trajectories of injection drug use and identify associated factors.

DESIGN

Data were derived from the Vancouver Injection Drug Users Study and AIDS Care Cohort to evaluate the Exposure to Survival Services study, two prospective cohorts involving people who inject drugs in Vancouver, Canada between 1996 and 2017. Growth mixture modeling was applied to identify distinct injection drug use trajectories. Multinomial logistic regression was used to identify baseline factors associated with each trajectory.

SETTING

Canada.

PARTICIPANTS

A total of 2057 participants who reported having used illicit drugs via injection in the past 6 months at the baseline visit were included in the study. The median time since first injection drug use at baseline was 14.8 years (quartile 1-quartile 3: 6.5-24.3).

MEASUREMENTS

Information regarding self-reported injection drug use during the past 6 months was collected at baseline and semi-annually thereafter via interviewer-administered questionnaires.

FINDINGS

Participants were followed for a median of 113.4 months (quartile 1-quartile 3: 63.4-161.7). Five trajectories were identified: persistent high frequency injection (507, 24.6%); high frequency injection with late decrease (374, 18.2%); gradual cessation (662, 32.2%); early cessation with late relapse (227, 11.0%); and early cessation (287, 14.0%). Factors found to be associated with distinct trajectories included: daily heroin injection, binge injection drug use, age, not being in a stable relationship and year of study enrollment.

CONCLUSIONS

People who used drugs in Vancouver, Canada from 1996 to 2017 appeared to follow five drug use trajectories, ranging from persistent high frequency use to early cessation. Almost 25% of participants remained high-frequency injectors over the study period.

Longitudinal migration patterns from an open illicit drug scene among people who use illicit drugs in Vancouver, Canada

The objective of this study was to identify migration patterns from an open illicit drug scene (the Downtown Eastside [DTES] neighborhood) and describe factors associated with these migration patterns. Data were derived from three cohorts of people who use illicit drugs in Vancouver, Canada. Defined using latent class growth analysis, we identified four distinct migration trajectory groups: 1) consistently living in the DTES (47.8%); 2) early migration out, with a median time of migrating out of DTES of 5.3 months (21.5%); 3) late migration out, with a median time of migrating out of DTES of 38.0 months (20.1%); and 4) frequent revisit back-and-forth to DTES (10.6%). In a multivariable model, compared to the "consistently living in the DTES" group, factors associated with the "frequent revisit" group included being enrolled in non-pharmacological addiction treatment and having an HCV-positive serostatus. Factors associated with the "early migration out" group included being enrolled in detoxification or in other non-pharmacological addiction treatment, later calendar year, being on income assistance, living in a single room occupancy hotel, and having an HCV-positive serostatus. These findings point to the need for appropriate distribution of services in order to meet the needs of this population.

Trajectories of heroin use: A 15-year retrospective study of Mexican-American men who were affiliated with gangs during adolescence

BACKGROUND

Heroin use is a public health concern in the United States. Despite the unique etiology and patterns of heroin use among U.S. Latinos, long-term heroin trajectories and health consequences among Latinos are not well understood. This study aims to document the distinct heroin use trajectories for a group of street-recruited (non-treatment), young adult Mexican American men living in a disadvantaged community who were affiliated with gangs during their youth.

METHODS

One-time interviews conducted between 2009-2012 in San Antonio, TX collected retrospective data from a sample of 212 Mexican American young adult men who reported using heroin at least once. Group-based trajectory modeling was applied to determine discrete developmental trajectories of heroin use. ANOVA, Chi square tests, and multinomial logistic regression examined current (past year) social and health indicators among each trajectory group.

RESULTS

Five discrete heroin trajectories groups were identified: low use (n = 65); late accelerating (n = 31); early decelerating (n = 26); late decelerating (n = 38); and stably high (n = 52). Varying social and health consequences were found among the trajectory groups.

CONCLUSION

This study describes the unique heroin use trajectories and social and health outcomes among a high-risk subgroup of Mexican American men. The findings suggest that early intervention and intervention available in easy to access non-treatment spaces may be especially useful for groups of people who use relatively less heroin.

Opioid agonist treatment scale-up and the initiation of injection drug use: A dynamic modeling analysis

BACKGROUND

Injection drug use (IDU) is associated with multiple health harms. The vast majority of IDU initiation events (in which injection-naïve persons first adopt IDU) are assisted by a person who injects drugs (PWID), and as such, IDU could be considered as a dynamic behavioral transmission process. Data suggest that opioid agonist treatment (OAT) enrollment is associated with a reduced likelihood of assisting with IDU initiation. We assessed the association between recent OAT enrollment and assisting IDU initiation across several North American settings and used dynamic modeling to project the potential population-level impact of OAT scale-up within the PWID population on IDU initiation.

METHODS AND FINDINGS

We employed data from a prospective multicohort study of PWID in 3 settings (Vancouver, Canada [n = 1,737]; San Diego, United States [n = 346]; and Tijuana, Mexico [n = 532]) from 2014 to 2017. Site-specific modified Poisson regression models were constructed to assess the association between recent (past 6 month) OAT enrollment and history of ever having assisted an IDU initiation with recently assisting IDU initiation. Findings were then pooled using linear mixed-effects techniques. A dynamic transmission model of IDU among the general population was developed, stratified by known factors associated with assisting IDU initiation and relevant drug use behaviors. The model was parameterized to a generic North American setting (approximately 1% PWID) and used to estimate the impact of increasing OAT coverage among PWID from baseline (approximately 21%) to 40%, 50%, and 60% on annual IDU initiation incidence and corresponding PWID population size across a decade. From Vancouver, San Diego, and Tijuana, respectively, 4.5%, 5.2%, and 4.3% of participants reported recently assisting an IDU initiation, and 49.4%, 19.7%, and 2.1% reported recent enrollment in OAT. Recent OAT enrollment was significantly associated with a 45% lower likelihood of providing recent IDU initiation assistance among PWID (relative risk [RR] 0.55 [95% CI 0.36-0.84], p = 0.006) compared to those not recently on OAT. Our dynamic model predicts a baseline mean of 1,067 (2.5%-97.5% interval [95% I 490-2,082]) annual IDU initiations per 1,000,000 individuals, of which 886 (95% I 406-1,750) are assisted by PWID. Based on our observed statistical associations, our dynamic model predicts that increasing OAT coverage from approximately 21% to 40%, 50%, or 60% among PWID could reduce annual IDU initiations by 11.5% (95% I 2.4-21.7), 17.3% (95% I 5.6-29.4), and 22.8% (95% I 8.1-36.8) and reduce the PWID population size by 5.4% (95% I 0.1-12.0), 8.2% (95% I 2.2-16.9), and 10.9% (95% I 3.2-21.8) relative to baseline, respectively, in a decade. Less impact occurs when the protective effect of OAT is diminished, when a greater proportion of IDU initiations are unassisted by PWID, and when average IDU career length is longer. The study's main limitations are uncertainty in the causal pathway between OAT enrollment and assisting with IDU initiation and the use of a simplified model of IDU initiation.

CONCLUSIONS

In addition to its known benefits on preventing HIV, hepatitis C virus (HCV), and overdose among PWID, our modeling suggests that OAT scale-up may also reduce the number of IDU initiations and PWID population size.

Engagement in treatment for depression among people who inject drugs in Baltimore, Maryland

INTRODUCTION

Mental health care may mitigate negative consequences related to substance use and bolster engagement in care for drug dependence. Despite the increased risk of depression among people who inject drugs (PWID), the longitudinal relationship of depression symptoms with depression and drug treatment utilization in this population remains uncharacterized.

METHODS

Data on depressive symptoms and depression treatment from current and former PWID in the ALIVE (AIDS Linked to the IntraVenous Experience) community-based cohort who had ≥3 study visits from July 2005 to June 2016 were included. We used logistic regression analysis with generalized estimating equations to examine factors associated with depression treatment in the 12 months following reported major depressive symptoms (CES-D ≥ 23) in the absence of treatment. We further examined the association between depression, depression treatment, and subsequent engagement in drug treatment among those with active substance use or alcohol dependence.

RESULTS

Of the 1544 participants, 34% were female, the median age was 51 years, and 91% were African-American. PWID reported major depressive symptoms at 22% of study visits. In adjusted analysis, acute emergency care, suicidal ideation, and recent alcohol or drug treatment were positively associated with initiating depression treatment. Depression was positively associated with subsequent treatment for substance dependence among those actively using (aOR = 1.30, 95% CI: 1.10-1.53).

CONCLUSIONS

PWID experience a high burden of depressive symptoms with significant unmet need of treatment for depression. Our findings suggest that mental health providers should bolster connections to chronic disease and alcohol and drug treatment providers.

Opioid Addiction, Genetic Susceptibility, and Medical Treatments: A Review

Opioid addiction is a chronic and complex disease characterized by relapse and remission. In the past decade, the opioid epidemic or opioid crisis in the United States has raised public awareness. Methadone, buprenorphine, and naloxone have proven their effectiveness in treating addicted individuals, and each of them has different effects on different opioid receptors. Classic and molecular genetic research has provided valuable information and revealed the possible mechanism of individual differences in vulnerability for opioid addiction. The polygenic risk score based on the results of a genome-wide association study (GWAS) may be a promising tool to evaluate the association between phenotypes and genetic markers across the entire genome. A novel gene editing approach, clustered, regularly-interspaced short palindromic repeats (CRISPR), has been widely used in basic research and potentially applied to human therapeutics such as mental illness; many applications against addiction based on CRISPR are currently under research, and some are successful in animal studies. In this article, we summarized the biological mechanisms of opioid addiction and medical treatments, and we reviewed articles about the genetics of opioid addiction, the promising approach to predict the risk of opioid addiction, and a novel gene editing approach. Further research on medical treatments based on individual vulnerability is needed.

Modelling Long-Term Joint Trajectories of Heroin Use and Treatment Utilisation: Findings from the Australian Treatment Outcome Study

BACKGROUND

Heroin is currently contributing to the worst drug addiction epidemic in United States history; recent rates of use, dependence and death have also increased dramatically in parts of Europe. An improved understanding of the long-term relationship between heroin use and treatment utilisation is essential to inform both clinical and public health responses. We aimed to identify i) joint trajectories of heroin use and treatment utilisation, ii) predictors of joint group membership, and iii) outcomes associated with joint group membership; over 10-11 years among a cohort of Australians with heroin dependence.

METHODS

A total of 615 people with heroin dependence were recruited as part of a prospective longitudinal cohort study between 2001 and 02. This analysis focuses on 428 participants (70.1% of the original cohort) for whom complete data were available over 10-11 years.

FINDINGS

Five joint trajectory groups were identified: i) 'long-term stable' (17%: decrease in probability of heroin use alongside high treatment utilisation); ii) 'long-term success' (13%: decrease in heroin use alongside decreased treatment utilisation, until there was maintained abstinence from heroin with no treatment utilisation); iii) 'treatment failure' (12%: no decrease in heroin use alongside high treatment utilisation); iv) 'late success' (9%: gradual decrease in heroin use alongside increased treatment utilisation); and v) 'relapsed' (9%: relapse in heroin use alongside an increase and decrease in treatment utilisation). Few variables were found to predict joint group membership, but group membership was predictive of demographic, substance use and physical and mental health outcomes at 10-11 years.

INTERPRETATION

The role of treatment in recovery from heroin dependence is undeniable; however, a considerable proportion of people are able achieve and maintain abstinence without the need for ongoing treatment. An equally significant proportion will continue to use heroin despite being in long-term treatment.

FUNDING

Australian National Health and Medical Research Council.

The chippers, the quitters, and the highly symptomatic: A 12-month longitudinal study of DSM-5 opioid- and cocaine-use problems in a community sample

BACKGROUND

Individual trajectories of drug use and drug-related problems are highly heterogeneous. There is no standard taxonomy of these trajectories, but one could be developed by defining natural categories based on changes in symptoms of substance-use disorders over time.

METHODS

Our study was conducted in a community sample in Baltimore, Maryland. At baseline, all participants were using opioids and/or cocaine, but none were in treatment. Drug use and symptomatology were assessed again at 12 months (N = 115).

RESULTS

We defined Quitters as participants who had not used for at least 30 days at follow-up (17%). For the remaining participants, we performed longitudinal cluster analysis on DSM symptom-counts, identifying three trajectory clusters: newly or persistently Symptomatic (40%) participants, Chippers (21.5%) with few symptoms, and Converted Chippers (21.5%) with improved symptom counts. Logistic regression showed that profiles of Quitters did not resemble Chippers, but instead resembled Symptomatic participants, having high probability of disorderly home neighborhood, nonwhite race, and negative mood. Quitters tended to have two protective factors: initiating opioid-agonist treatment during the study (r_effect = 0.25, CL95 0.02-0.48) and lack of polydrug use (r_effect = 0.25, CL95 0.004-0.49). Converted Chippers tended to be white, with orderly home neighborhoods and less negative mood (r_effects 0.24 to 0.31, CL95 0.01-0.54).

CONCLUSIONS

Changes in DSM symptomology provided a meaningful measure of individual trajectories. Quitters shared psychosocial characteristics with Symptomatic participants, but not with participants who continued to use with few symptoms. This suggests that Quitters abstained out of necessity, not because their problems were less severe.

Supervised Injection Facility Utilization Patterns: A Prospective Cohort Study in Vancouver, Canada

INTRODUCTION

Although the health and community benefits of supervised injection facilities are well documented, little is known about long-term patterns of utilization of this form of health service. The present study seeks to longitudinally characterize discontinuation of use of a supervised injection facility in Vancouver, Canada.

METHODS

Data were drawn from 2 community-recruited prospective cohorts of people who inject drugs between December 2005 and December 2016. In 2018, extended Cox regression for recurrent events was used to examine factors associated with time to cessation of supervised injection facility use during periods of active injection.

RESULTS

Of 1,336 people who inject drugs that were followed for a median of 50 months, 847 (63.4%) participants reported 1,663 6-month periods of supervised injection facility use cessation while actively injecting drugs (incidence density of 26.6 events per 100 person-years). An additional 2,282 (57.8%) of the total 3,945 6-month periods of supervised injection facility use cessation occurred during periods of injection cessation. In multivariable analyses, enrollment in methadone maintenance therapy (adjusted hazard ratio=1.41) and HIV seropositivity (adjusted hazard ratio=1.23) were positively associated with supervised injection facility use cessation during periods of active injection, whereas homelessness (adjusted hazard ratio=0.59), at least daily heroin injection (adjusted hazard ratio=0.70), binge injection (adjusted hazard ratio=0.68), public injection (adjusted hazard ratio=0.67), nonfatal overdose (adjusted hazard ratio=0.73), difficulty accessing addiction treatment (adjusted hazard ratio=0.69), and incarceration (adjusted hazard ratio=0.70) were inversely associated with this outcome (all p<0.05). The most commonly reported reasons for supervised injection facility use cessation were injection drug use cessation (42.3%) and a preference for injecting at home (30.7%).

CONCLUSIONS

These findings suggest that this supervised injection facility successfully retains people who inject drugs at elevated risk of drug-related harms and indicate that many supervised injection facility clients neither use this service nor inject drugs perpetually.

Short and sporadic injecting cessation episodes as predictors of incident hepatitis C virus infection: findings from a cohort study of people who inject drugs in Montréal, Canada

BACKGROUND AND AIMS

For most people who inject drugs (PWID), drug injecting follows a dynamic process characterized by transitions in and out of injecting. The objective of this investigation was to examine injecting cessation episodes of 1-3-month duration as predictors of hepatitis C virus (HCV) acquisition.

DESIGN

Cohort study.

SETTING

Montréal, Canada.

PARTICIPANTS

A total of 372 HCV-uninfected (HCV RNA-negative, HCV antibody-positive or -negative) PWID (mean age = 39.3 years, 82% male, 45% HCV antibody-positive) enrolled between March 2011 and June 2016.

MEASUREMENTS

At 3-month intervals, participants completed an interviewer-administered questionnaire and were tested for HCV particles (HCV RNA). At each visit, participants indicated whether they injected in each of the past 3 months (defined as three consecutive 30-day periods). Injecting cessation patterns were evaluated on a categorical scale: persistent injecting (no injecting cessation in the past 3 months), sporadic injecting cessation (injecting cessation in 1 of 3 or 2 of 3 months) and short injecting cessation (injecting cessation in 3 of 3 months). Their association with HCV infection risk was examined using Cox regression analyses with time-dependent covariates, including age, gender, incarceration, opioid agonist treatment and other addiction treatments.

FINDINGS

At baseline, 61, 26 and 13% of participants reported persistent injecting, sporadic injecting cessation and short injecting cessation, respectively. HCV incidence was 7.5 per 100 person-years [95% confidence interval (CI) = 5.9-9.5; 916 person-years of follow-up]. In adjusted Cox models, sporadic injecting cessation and short injecting cessation were associated with lower risks of incident HCV infection compared to persistent injecting (adjusted hazard ratios = 0.56, 95% CI = 0.30-1.04 and 0.24, 95% CI = 0.09-0.61), respectively.

CONCLUSION

Short and sporadic injecting cessation episodes were common among a cohort of people who inject drugs in Montréal, Canada. Injecting cessation episodes appear to be protective against hepatitis C virus acquisition, particularly when maintained for at least 3 months.

Young people who inject drugs in India have high HIV incidence and behavioural risk: a cross-sectional study

INTRODUCTION

There are limited data on young people who inject drugs (PWID) from low- and middle-income countries where injection drug use remains a key driver of new HIV infections. India has a diverse injection drug use epidemic and estimates suggest that at least half of PWID are ≤30 years of age. We compared injection and sexual risk behaviours and HIV incidence between younger and older PWID and characterized uptake of HIV testing and harm reduction services to inform targeted HIV prevention efforts.

METHODS

We analysed cross-sectional data from 14,381 PWID recruited from cities in the Northeast and North/Central regions of India in 2013 using respondent driven sampling (RDS). We compared "emerging-adult" (18 to 24 years, 26% of sample) and "young-adult" PWID (25 to 30 years, 30% of sample) to older PWID (>30 years, 44% of sample) using logistic regression to evaluate factors associated with three recent risk behaviours: needle-sharing, multiple sexual partners and unprotected sex. We estimated age-stratified cross-sectional HIV incidence using a validated multi-assay algorithm.

RESULTS

Compared to older adults, emerging-adults in the Northeastern states were significantly more likely to share needles (males adjusted odds ratio [aOR] 1.82; females aOR 2.29, p < 0.01), have multiple sexual partners (males aOR 1.56; females aOR 3.75, p < 0.01), and engage in unprotected sex (males aOR 2.29, p < 0.01). In the North/Central states, young-adult males were significantly more likely to needle-share (aOR 1.23, p < 0.05) while emerging-adult males were significantly more likely to have multiple sexual partners (aOR 1.74, p < 0.05). In both regions, emerging-adults had the lowest HIV testing. Participation in harm reduction services was low across all age groups. Annual HIV incidence was higher in emerging- and young-adult PWID in the North/Central region: emerging-adults: 4.3% (95% confidence interval [CI] 3.0, 5.6); young-adults: 4.9% (95% CI 3.7, 6.2); older adults: 2.1% (95% CI 1.4, 2.8).

CONCLUSIONS

Higher HIV incidence and engagement in risky behaviours among younger PWID compared to older PWID, coupled with low utilization of harm reduction services highlight the importance of targeting this population in HIV programming. Age-specific interventions focused on addressing the needs of young PWID are urgently needed to curb the HIV epidemic in this vulnerable population.

Hepatitis C virus prevalence and estimated incidence among new injectors during the opioid epidemic in New York City, 2000-2017: Protective effects of non-injecting drug use

OBJECTIVE

Assess hepatitis C virus (HCV) prevalence and incidence among person who began injecting drugs during the opioid epidemic in New York City (NYC) and identify possible new directions for reducing HCV infection among persons who inject drugs.

METHODS

846 persons who began injecting drugs between 2000 and 2017 were recruited from persons entering Mount Sinai Beth Israel substance use treatment programs. A structured interview was administered and HCV antibody testing conducted. Protective effects of non-injecting drug use were examined among persons who "reversed transitioned" to non-injecting drug use and persons who used non-injected heroin in addition to injecting.

RESULTS

Participants were 79% male, 41% White, 15% African-American, 40% Latinx, with a mean age of 35. Of those who began injecting in 2000 or later, 97 persons (11%) "reverse transitioned" back to non-injecting drug use. Reverse transitioning was strongly associated with lower HCV seroprevalence (30% versus 47% among those who continued injecting, p < 0.005). Among those who continued injecting, HCV seropositivity was inversely associated with current non-injecting heroin use (AOR = 0.72, 95%CI 0.52-0.99). HCV incidence among persons continuing to inject was estimated as 13/100 person-years. HCV seropositive persons currently injecting cocaine were particularly likely to report behavior likely to transmit HCV.

CONCLUSIONS

Similar to other locations in the US, NYC is experiencing high rates of HCV infection among persons who have begun injecting since 2000. New interventions that facilitate substitution of non-injecting for injecting drug use and that reduce transmission behavior among HCV seropositives may provide additional methods for reducing HCV transmission.

6th Canadian Symposium on Hepatitis C Virus: Delivering a cure for hepatitis C infection—What are the remaining gaps?

Estimates are that more than 250,000 people in Canada are chronically infected with hepatitis C virus (HCV), and many more are unaware of their infection status. If untreated, chronic HCV infection can lead to cirrhosis and subsequent complications such as hepatocellular carcinoma. The Canadian Network on Hepatitis C, supported by the Public Health Agency of Canada and the Canadian Institutes of Health Research, has been committed to the scientific study of chronic hepatitis C and to supporting the advocacy work to improve diagnosis and access to HCV care in Canada. Although the treatment of HCV infection has been greatly advanced with direct-acting antivirals, with cure rates as high as 95%, many challenges remain in the implementation of HCV care. These issues include the lack of an effective vaccine, infection screening, treatment failure or resistance, post-cure health issues, limitations of treatment access despite increased provincial subsidization, complex needs of at-risk populations (ie, injection drug users, societal obstacles). At the 6th Canadian Symposium on HCV in March 2017, the theme “Delivering a Cure for Hepatitis C Infection: What Are the Remaining Gaps?” provided a framework in which basic scientists, clinicians, epidemiologists, social scientists, and community members interested in HCV research in Canada could showcase how they are working to address these ongoing challenges.

Predictors of injecting cessation among a cohort of people who inject drugs in Tijuana, Mexico

INTRODUCTION

Little is known about the cessation of injecting drug use (IDU) among people who inject drugs (PWID) in low and middle-income settings, where access to effective interventions for reducing drug use (e.g., opioid substitution treatment; OST), may be limited. We measured the incidence and identified predictors of IDU cessation among a cohort of PWID in Tijuana, Mexico.

METHODS

Data were drawn from 621 participants in Proyecto El Cuete IV, a prospective cohort of PWID recruited in 2011 and interviewed biannually to 2016. A multivariable Extended Cox model was constructed to identify socio-demographic, drug use, risk environment and health-related predictors of IDU cessation (no IDU for ≥six months).

RESULTS

141 participants (23%) reported at least one IDU cessation event during follow-up. The crude IDU cessation rate was 7.3 per 100 person-years (95% Confidence Interval [CI]: 6.2-8.7). IDU cessation was negatively associated with injecting at least daily on average and heroin/methamphetamine co-injection in the past six months, and positively associated with testing HIV positive at baseline, being on methadone maintenance therapy in the past six months, and recent arrest. Concern for personal safety was also independently associated with IDU cessation.

CONCLUSIONS

The rate of IDU cessation among PWID in Tijuana was low. These findings underscore the importance of expansion of services including OST to help reduce drug use and facilitate IDU cessation for those who wish to do so. In this setting, interventions addressing individual-level economic barriers as well as broader social and structural barriers to harm reduction services are integral.

The next wave of hepatitis C virus: The epidemic of intravenous drug use

The epidemic of hepatitis C virus (HCV) began in the 1960s when transmission was primarily the result of blood transfusions. By 1990, when HCV was identified and a serologic test for screening donated blood was implemented, 123 million persons had already become infected worldwide and HCV was the most common cause of cirrhosis, hepatocellular carcinoma and the most common indication for liver transplantation. Approximately 75% of persons with HCV are "baby boomers" born between the years 1945 and 1965. The number of new cases of HCV declined precipitously between 1990 and 2005. The next wave of HCV began in 2005, and transmission is primarily the result of an epidemic of intravenous drug use. New cases of HCV have increased three-fold between 2005 and 2015. Approximately 50% of persons who inject drugs (PWID) have been exposed to HCV, and 25% of these persons are under the age of 25 years. The treatment of chronic HCV in PWID has two goals; treating HCV and preventing the patient from returning to drug use and becoming reinfected. Highly effective oral antiviral agents are now available and can cure HCV in virtually all patients. Treatment can be highly effective in PWID with sustained virologic response rates similar to that observed in a non-drug-using population. Preventing the patient from returning to drug use and becoming reinfected with HCV is more difficult and will require that the medical and social problems associated with intravenous drug use be addressed and resolved.

Post-war prevention: Emerging frameworks to prevent drug use after the War on Drugs

The prevention of drug use is one of the primary goals of the War on Drugs. However, despite investment in high-profile interventions such as social marketing campaigns and enforcement-based deterrence, these efforts have generally failed. With the emergence of novel policy frameworks to control and regulate drug use, a window of opportunity exists to test approaches to drug prevention that take into account existing evidence and the rights of individuals who use drugs. Specifically, there is a growing consensus that entry into drug use is a socially-defined event that individuals experience within particular socio-structural contexts. This understanding, coupled with a distinction between the value of preventing problematic drug use rather than all drug use, provides a useful framework within which to develop effective and rights-based approaches to drug prevention.

Heroin Use and Drug Injection among Youth Also Misusing Prescription Drugs

OBJECTIVES

We identified the prevalence of nonmedical prescription drug use and its relationship to heroin and injection drug use in 4 nationally representative samples of adolescents.

METHODS

We used the most recent data (2009-2015) from the Youth Risk Behavior Surveillance System (Ntotal= 61,132). Prevalence rates and 95% confidence intervals for prescription drug misuse, heroin use, and injection drug use were calculated across time points, sex, and race/ethnicity subgroups. Using odds ratios, we determined the likelihood of youth reporting nonmedical prescription drug use also reporting heroin and drug injection.

RESULTS

In 2015, one in 6 adolescents reported recent prescription drug misuse. High rates of nonmedical prescription drug use persisted or increased among Hispanic boys, black boys, and "other" youth, while declining among white youth. Youth who used prescription drugs nonmedically at least once were 17.5 times more likely to have used heroin (CI: 13.7, 22.4) and 14.6 times more likely to have injected drugs (CI: 11.2, 19.2) in their lifetime.

CONCLUSIONS

Public health programming focused on reducing prescription drug misuse also may reduce youth engagement in heroin and/or injection drug use. Preventive efforts to support communities of color in reducing rates of prescription drug misuse are crucial.

Seroprevalence of HCV and HIV infection among clients of the nation's longest-standing statewide syringe exchange program: A cross-sectional study of Community Health Outreach Work to Prevent AIDS (CHOW)

BACKGROUND

The Community Health Outreach Work to Prevent AIDS (CHOW) Project is the first and longest-standing statewide integrated and funded needle and syringe exchange program (SEP) in the US. Initiated on O'ahu in 1990, CHOW expanded statewide in 1993. The purpose of this study is to estimate the prevalences of hepatitis C virus (HCV) and human immunodeficiency virus (HIV) infection, and to characterize risk behaviors associated with infection among clients of a long-standing SEP through the analysis of the 2012 CHOW evaluation data.

METHODS

A cross-sectional sample of 130 CHOW Project clients was selected from January 1, 2012 through December 31, 2012. Questionnaires captured self-reported exposure information. HIV and HCV antibodies were detected via rapid, point-of-care FDA-approved tests. Log-binomial regressions were used to estimate prevalence proportion ratios (PPRs). A piecewise linear log-binomial regression model containing 1 spline knot was used to fit the age-HCV relationship.

RESULTS

The estimated seroprevalence of HCV was 67.7% (95% confidence interval [CI]=59.5-75.8%). HIV seroprevalence was 2.3% (95% CI=0-4.9%). Anti-HCV prevalence demonstrated age-specific patterns, ranging from 31.6% through 90.9% in people who inject drugs (PWID) <30 to ≥60 years respectively. Age (continuous/year) prior to spline knot at 51.5 years (adjusted PPR [APPR]=1.03; 95% CI=1.02-1.05) and months exchanging syringes (quartiles) (APPR=1.92; 95% CI=1.3-3.29) were independently associated with anti-HCV prevalence.

CONCLUSION

In Hawai'i, HCV prevalence among PWID is hyperendemic demonstrating age- and SEP duration-specific trends. Relatively low HIV prevalence compared with HCV prevalence reflects differences in transmissibility of these 2 blood-borne pathogens and suggests much greater efficacy of SEP for HIV prevention.

Re-examining blood donor deferral criteria relating to injecting drug use

BACKGROUND AND AIMS

Potential Australian blood donors are deferred indefinitely if they report a history of injecting drug use (IDU), or for 12 months if they report having engaged in sexual activity with someone who might have ever injected. Given incremental improvements in blood safety, this study sought to examine whether Australia's IDU-related eligibility criteria reflected current scientific evidence, were consistent with international best practice and, if current IDU-related policies were to be changed, how this should happen.

METHODS

An expert committee was formed to review relevant literature with a focus on issues including: the epidemiology of IDU in Australia and key transfusion-transmissible infections (TTIs) among Australian people who inject drugs (PWID); and, 'non-compliance' among PWID regarding IDU-related blood donation guidelines. International policies relating to blood donation and IDU were also reviewed. Modelling with available data estimated the risk of TTIs remaining undetected if the Blood Service's IDU-related guidelines were changed.

RESULTS

Very few (<1%) Australians engage in IDU, and IDU risk practices are reported by only a minority of PWID. However, the prevalence of HCV remains high among PWID, and IDU remains a key transmission route for various TTIs. Insufficient data were available to inform appropriate estimates of cessation and relapse among Australian PWID. Modelling findings indicated that the risk of not detecting HIV becomes greater than the reference group at a threshold of non-admission of being an active PWID of around 1.8% (0.5-5.1%). Excluding Japan, all Organisation for the Economic Co-operation and Development member countries permanently exclude individuals with a history of IDU from donating.

CONCLUSION

Numerous research gaps meant that the study's expert Review Committee was unable to recommend altering Australia's current IDU-related blood donation guidelines. However, having identified critical knowledge gaps and future areas of research, the review made important steps toward changing the criteria.

Trajectories of heroin use: 10-11-year findings from the Australian Treatment Outcome Study

AIMS

To identify trajectories of heroin use in Australia, predictors of trajectory group membership and subsequent outcomes among people with heroin dependence over 10-11 years.

DESIGN

Longitudinal cohort study.

SETTING

Sydney, Australia.

PARTICIPANTS

A total of 615 participants were recruited between 2001 and 2002 as part of the Australian Treatment Outcome Study (66.2% male; mean age 29 years). The predominance of the cohort (87.0%) was recruited upon entry to treatment (maintenance therapies, detoxification and residential rehabilitation), and the remainder from non-treatment settings (e.g. needle and syringe programmes). This analysis focused upon 428 participants for whom data on heroin use were available over 10-11 years following study entry.

MEASUREMENTS

Structured interviews assessed demographics, treatment history, heroin and other drug use, overdose, criminal involvement, physical health and psychopathology. Group-based trajectory modelling was used to: (i) identify trajectory groups based on use of heroin in each year, (ii) examine predictors of group membership and (iii) examine associations between trajectory group membership and 10-11-year outcomes.

FINDINGS

Six trajectory groups were identified [Bayesian Information Criterion (BIC) = -1927.44 (n = 4708); -1901.07 (n = 428)]. One in five (22.1%) were classified as having 'no decrease' in heroin use, with the probability of using remaining high during the 10-11 years (> 0.98 probability of use in each year). One in six (16.1%) were classified as demonstrating a 'rapid decrease to maintained abstinence'. The probability of heroin use among this group declined steeply in the first 2-3 years and continued to be low (< 0.01). The remaining trajectories represented other fluctuating patterns of use. Few baseline variables were found to predict trajectory group membership, but group membership was predictive of demographic, substance use and physical and mental health outcomes at 10-11 years.

CONCLUSIONS

Long-term trajectories of heroin use in Australia appear to show considerable heterogeneity during a decade of follow-up, with few risk factors predicting group membership. Just more than a fifth continued to use at high levels, while fewer than a fifth become abstinent early on and remained abstinent. The remainder showed fluctuating patterns.

Mitigating the heroin crisis in Baltimore, MD, USA: a cost-benefit analysis of a hypothetical supervised injection facility

Background

In Baltimore, MD, as in many cities throughout the USA, overdose rates are on the rise due to both the increase of prescription opioid abuse and that of fentanyl and other synthetic opioids in the drug market. Supervised injection facilities (SIFs) are a widely implemented public health intervention throughout the world, with 97 existing in 11 countries worldwide. Research has documented the public health, social, and economic benefits of SIFs, yet none exist in the USA. The purpose of this study is to model the health and financial costs and benefits of a hypothetical SIF in Baltimore.

Methods

We estimate the benefits by utilizing local health data and data on the impact of existing SIFs in models for six outcomes: prevented human immunodeficiency virus transmission, Hepatitis C virus transmission, skin and soft-tissue infection, overdose mortality, and overdose-related medical care and increased medication-assisted treatment for opioid dependence.

Results

We predict that for an annual cost of $1.8 million, a single SIF would generate $7.8 million in savings, preventing 3.7 HIV infections, 21 Hepatitis C infections, 374 days in the hospital for skin and soft-tissue infection, 5.9 overdose deaths, 108 overdose-related ambulance calls, 78 emergency room visits, and 27 hospitalizations, while bringing 121 additional people into treatment.

Conclusions

We conclude that a SIF would be both extremely cost-effective and a significant public health and economic benefit to Baltimore City.

Social causation and neighborhood selection underlie associations of neighborhood factors with illicit drug-using social networks and illicit drug use among adults relocated from public housing

Theories of social causation and social influence, which posit that neighborhood and social network characteristics are distal causes of substance use, are frequently used to interpret associations among neighborhood characteristics, social network characteristics and substance use. These associations are also hypothesized to result from selection processes, in which substance use determines where people live and who they interact with. The potential for these competing selection mechanisms to co-occur has been underexplored among adults. This study utilizes path analysis to determine the paths that relate census tract characteristics (e.g., economic deprivation), social network characteristics (i.e., having ≥ 1 illicit drug-using network member) and illicit drug use, among 172 African American adults relocated from public housing in Atlanta, Georgia and followed from 2009 to 2014 (7 waves). Individual and network-level characteristics were captured using surveys. Census tract characteristics were created using administrative data. Waves 1 (pre-relocation), 2 (1st wave post-relocation), and 7 were analyzed. When controlling for individual-level sociodemographic factors, residing in census tracts with prior economic disadvantage was significantly associated with illicit drug use at wave 1; illicit drug use at wave 1 was significantly associated with living in economically-disadvantaged census tracts at wave 2; and violent crime at wave 2 was associated with illicit drug-using social network members at wave 7. Findings from this study support theories that describe social causation and neighborhood selection processes as explaining relationships of neighborhood characteristics with illicit drug use and illicit drug-using social networks. Policies that improve local economic and social conditions of neighborhoods may discourage substance use. Future studies should further identify the barriers that prevent substance users from obtaining housing in less disadvantaged neighborhoods.

From Long-Term Injecting to Long-Term Non-Injecting Heroin and Cocaine Use: The Persistence of Changed Drug Habits

OBJECTIVES

Transitioning from injecting to non-injecting routes of drug administration can provide important individual and community health benefits. We assessed characteristics of persons who had ceased injecting while continuing to use heroin and/or cocaine in New York City.

METHODS

We recruited subjects entering Mount Sinai Beth Israel detoxification and methadone maintenance programs between 2011 and 2015. Demographic information, drug use histories, sexual behaviors, and "reverse transitions" from injecting to non-injecting drug use were assessed in structured face-to-face interviews. There were 303 "former injectors," operationally defined as persons who had injected at some time in their lives, but had not injected in at least the previous 6 months. Serum samples were collected for HIV and HCV testing.

RESULTS

Former injectors were 81% male, 19% female, 17% White, 43% African-American, and 38% Latino/a, with a mean age of 50 (SD=9.2), and were currently using heroin and/or cocaine. They had injected drugs for a mean of 14 (SD=12.2) years before ceasing injection, and a mean of 13 (SD=12) years had elapsed since their last injection. HIV prevalence among the sample was 13% and HCV prevalence was 66%. The former injectors reported a wide variety of reasons for ceasing injecting. Half of the group appeared to have reached a point where relapse back to injecting was no longer problematic: they had not injected for three or more years, were not deliberately using specific techniques to avoid relapse to injecting, and were not worried about relapsing to injecting.

CONCLUSIONS

Former injectors report very-long term behavior change toward reduced individual and societal harm while continuing to use heroin and cocaine. The behavior change appears to be self-sustaining, with full replacement of an injecting route of drug administration by a non-injecting route of administration. Additional research on the process of long-term cessation of injecting should be conducted within a "combined prevention and care" approach to HIV and HCV infection among persons who use drugs.