Incidence and determinants of initiation into cocaine injection and correlates of frequent cocaine injectors

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.

Social determinants of ethno-racial inequalities in substance use: a decomposition of national survey data

BACKGROUND

Similar to the US, mortality due to suicide and the use of opioids, alcohol, and other substances (so-called "Deaths of Despair"), is rising in Canada and has been disproportionately observed among Whites compared to other racial and ethnic groups. This study aimed to assess the determinants of the ethno-racial differences in the use of substances that underlie these deaths.

METHODS

Using nationally representative data from the Canadian Community Health Survey (2003, 2015-2016, 2018 cycles), a decomposition analysis was performed to estimate the contribution of psychosocial determinants, including age, sex, marital status, immigration, education, income, rurality, and affective health on inequalities between White and non-White populations in illicit substance, opioid, and problematic alcohol use and combined use (≥ 2) of substances.

RESULTS

Overall, White respondents reported higher levels (by 5% to 10%) of substance use than non-White peers. Over 30% of the ethno-racial inequalities in illicit substance, problematic alcohol, and polysubstance use are explained by the protective role of immigration among those who are not White, whose low levels of substance use lower the prevalence in the non-White population overall. Among those born in Canada, no ethno-racial differences in substance use were observed.

CONCLUSION

Social determinants, particularly immigrant status, explain a substantial proportion of ethno-racial inequalities in substance use in Canada. The jump in substance use between racialized populations who immigrated to Canada and those Canadian-born highlights the importance of exploring within-group variability in deaths of despair risk and considering how intersecting forces including systemic racism shape substance use patterns across generations.

Homelessness, unstable housing, and risk of HIV and hepatitis C virus acquisition among people who inject drugs: a systematic review and meta-analysis

BACKGROUND

People who inject drugs (PWID) are at increased risk for HIV and hepatitis C virus (HCV) infection and also have high levels of homelessness and unstable housing. We assessed whether homelessness or unstable housing is associated with an increased risk of HIV or HCV acquisition among PWID compared with PWID who are not homeless or are stably housed.

METHODS

In this systematic review and meta-analysis, we updated an existing database of HIV and HCV incidence studies published between Jan 1, 2000, and June 13, 2017. Using the same strategy as for this existing database, we searched MEDLINE, Embase, and PsycINFO for studies, including conference abstracts, published between June 13, 2017, and Sept 14, 2020, that estimated HIV or HCV incidence, or both, among community-recruited PWID. We only included studies reporting original results without restrictions to study design or language. We contacted authors of studies that reported HIV or HCV incidence, or both, but did not report on an association with homelessness or unstable housing, to request crude data and, where possible, adjusted effect estimates. We extracted effect estimates and pooled data using random-effects meta-analyses to quantify the associations between recent (current or within the past year) homelessness or unstable housing compared with not recent homelessness or unstable housing, and risk of HIV or HCV acquisition. We assessed risk of bias using the Newcastle-Ottawa Scale and between-study heterogeneity using the I2 statistic and p value for heterogeneity.

FINDINGS

We identified 14 351 references in our database search, of which 392 were subjected to full-text review alongside 277 studies from our existing database. Of these studies, 55 studies met inclusion criteria. We contacted the authors of 227 studies that reported HIV or HCV incidence in PWID but did not report association with the exposure of interest and obtained 48 unpublished estimates from 21 studies. After removal of duplicate data, we included 37 studies with 70 estimates (26 for HIV; 44 for HCV). Studies originated from 16 countries including in North America, Europe, Australia, east Africa, and Asia. Pooling unadjusted estimates, recent homelessness or unstable housing was associated with an increased risk of acquiring HIV (crude relative risk [cRR] 1·55 [95% CI 1·23-1·95; p=0·0002]; I2= 62·7%; n=17) and HCV (1·65 [1·44-1·90; p<0·0001]; I2= 44·8%; n=28]) among PWID compared with those who were not homeless or were stably housed. Associations for both HIV and HCV persisted when pooling adjusted estimates (adjusted relative risk for HIV: 1·39 [95% CI 1·06-1·84; p=0·019]; I2= 65·5%; n=9; and for HCV: 1·64 [1·43-1·89; p<0·0001]; I2= 9·6%; n=14). For risk of HIV acquisition, the association for unstable housing (cRR 1·82 [1·13-2·95; p=0·014]; n=5) was higher than for homelessness (1·44 [1·13-1·83; p=0·0036]; n=12), whereas no difference was seen between these outcomes for risk of HCV acquisition (1·72 [1·48-1·99; p<0·0001] for unstable housing, 1·66 [1·37-2·00; p<0·0001] for homelessness).

INTERPRETATION

Homelessness and unstable housing are associated with increased risk of HIV and HCV acquisition among PWID. Our findings support the development of interventions that simultaneously address homelessness and unstable housing and HIV and HCV transmission in this population.

FUNDING

National Institute for Health Research, National Institute on Drug Abuse, National Institute of Allergy and Infectious Diseases, and Commonwealth Scholarship Commission.

Examining the Association Between Psychiatric Disorders and Cocaine Binges: Results From the COSMO Study

OBJECTIVES

Although cocaine binges and mental health problems have both been identified as significant risk factors for different health hazards, little is known about the relationship between mental health and cocaine binging. Hence, the aim of this study is to examine the association between psychiatric disorders and cocaine binge.

METHODS

Participants were part of a prospective cohort study of individuals who either smoke or inject cocaine. The dependent variable, namely a cocaine binge within the past month, was defined as the repetitive use of large quantities of cocaine until the individual was unable to access more of the drug or was physically unable to keep using. Psychiatric disorders were assessed using the Composite International Diagnostic Interview and the Diagnostic Interview Schedule questionnaires. Logistic regression models were performed to examine the association between cocaine binging and psychiatric disorders, adjusting for potential confounders.

RESULTS

Of the 492 participants, 24.4% reported at least 1 cocaine binging episode during the prior month. Among the study population, 48.0% met the criteria for antisocial personality disorder (ASPD), 45.5% for anxiety disorders, and 28.2% for mood disorders. Participants with ASPD were more likely to binge (adjusted odds ratio 1.73, 95% confidence interval 1.10-2.73), whereas those with a mood disorder were not. The association between anxiety disorders and cocaine binging was significant only in univariate analyses.

CONCLUSION

ASPD increased the odds of reporting cocaine binge in our study population. These results highlight the need for a better understanding of the specific dimensions of ASPD that contribute to the increased risk of unsafe drug use behaviors.

Incarceration history and risk of HIV and hepatitis C virus acquisition among people who inject drugs: a systematic review and meta-analysis

BACKGROUND

People who inject drugs (PWID) experience a high prevalence of incarceration and might be at high risk of HIV and hepatitis C virus (HCV) infection during or after incarceration. We aimed to assess whether incarceration history elevates HIV or HCV acquisition risk among PWID.

METHODS

In this systematic review and meta-analysis, we searched MEDLINE, Embase, and PsycINFO databases for studies in any language published from Jan 1, 2000 until June 13, 2017 assessing HIV or HCV incidence among PWID. We included studies that measured HIV or HCV incidence among community-recruited PWID. We included only studies reporting original results and excluded studies that evaluated incident infections by self-report. We contacted authors of cohort studies that met the inclusion or exclusion criteria, but that did not report on the outcomes of interest, to request data. We extracted and pooled data from the included studies using random-effects meta-analyses to quantify the associations between recent (past 3, 6, or 12 months or since last follow-up) or past incarceration and HIV or HCV acquisition (primary infection or reinfection) risk among PWID. We assessed the risk of bias of included studies using the Newcastle-Ottawa Scale. Between-study heterogeneity was evaluated using the I2 statistic and the P-value for heterogeneity.

FINDINGS

We included published results from 20 studies and unpublished results from 21 studies. These studies originated from Australasia, western and eastern Europe, North and Latin America, and east and southeast Asia. Recent incarceration was associated with an 81% (relative risk [RR] 1·81, 95% CI 1·40-2·34) increase in HIV acquisition risk, with moderate heterogeneity between studies (I2=63·5%; p=0·001), and a 62% (RR 1·62, 95% CI 1·28-2·05) increase in HCV acquisition risk, also with moderate heterogeneity between studies (I2=57·3%; p=0·002). Past incarceration was associated with a 25% increase in HIV (RR 1·25, 95% CI 0·94-1·65) and a 21% increase in HCV (1·21, 1·02-1·43) acquisition risk.

INTERPRETATION

Incarceration is associated with substantial short-term increases in HIV and HCV acquisition risk among PWID and could be a significant driver of HCV and HIV transmission among PWID. These findings support the need for developing novel interventions to minimise the risk of HCV and HIV acquisition, including addressing structural risks associated with drug laws and excessive incarceration of PWID.

FUNDING

Engineering and Physical Sciences Research Council, National Institute for Health Research, National Institutes of Health.

Risk Factors Associated With Skin and Soft Tissue Infections Among Hospitalized People Who Inject Drugs

OBJECTIVES

Skin and soft tissue infections (SSTIs) are common among people who inject drugs (PWID), and can lead to serious morbidity and costly emergency room and hospital utilization. A range of high-risk injection practices may contribute to these infections. The goal of the current study was to examine risk practices that were associated with SSTIs in a sample of hospitalized PWID.

METHODS

PWID (N = 143; 40.6% female) were recruited from inpatient medical units at a large urban hospital and completed a baseline interview that focused on infection risk. Measures included demographics, substances used/injected, and self-report of SSTIs (ie, abscesses, ulcers, or cellulitis) within the past year. The Bacterial Infections Risk Scale for Injectors-a 7-item index-assessed specific behaviors expected to increase the risk of acquiring SSTIs (eg, injection without skin cleaning, intramuscular injection).

RESULTS

The sample was 58% Caucasian and averaged 38.7 (SD = 10.7) years of age. Ninety-three participants (65%) reported at least 1 SSTI within the past year. Using a logistic regression model, the Bacterial Infections Risk Scale for Injectors (odds ratio 1.87, P = 0.004) and total number of injections over the past 3 months (odds ratio 2.21, P = 0.002) were associated with past year SSTIs.

CONCLUSIONS

In conclusion, rates of past-year SSTIs were high in this sample of hospitalized PWID. Results suggest that interventions should target specific injection practices to reduce infection risk.

The costs of crime associated with stimulant use in a Canadian setting

BACKGROUND

Costs attributable to criminal activity are a major component of the economic burden of substance use disorders, yet there is a paucity of empirical evidence on this topic. Our aim was to estimate the costs of crime associated with different forms and intensities of stimulant use.

METHODS

Retrospective cohort study, including individuals from three prospective cohorts in Vancouver, Canada, measured biannually (2011-2015), reporting stimulant use at baseline assessment. Monthly crime costs included policing, court, corrections, and criminal victimization (2016 CAD). We estimated monthly crime costs associated with mutually exclusive categories of crack, cocaine, methamphetamine, and polystimulant use, stratified by daily/non-daily use, relative to stimulant abstinence, as well as the independent effects of treatment (opioid agonist (OAT) and other addiction treatment). We used a two-part model, capturing the probability of criminal activity and costs of crime with generalized linear logistic and gamma regression models, respectively, controlling for age, gender, education, homelessness, mental health issues, employment, prior incarceration, alcohol and opioid use.

RESULTS

The study sample included 1599 individuals (median age 39, 65.9% male) assessed over 5299 biannual interviews. Estimates of associated monthly crime costs ranged from $5449 [95% C.I.: $2180, $8719] for non-daily polystimulant use, to $8893 [$4196, $13,589] for daily polystimulant use. Cost differences between daily/non-daily use, injection/non-injection, and stimulant type were not statistically significant. Drug treatment was not associated with lower monthly crime costs in our sample.

CONCLUSIONS

Substantial crime-related costs were associated with stimulant use, emphasizing the urgency for development and implementation of efficacious treatment regimens.

Methadone maintenance therapy and viral suppression among HIV-infected opioid users: The impacts of crack and injection cocaine use

BACKGROUND

Methadone maintenance therapy (MMT) is associated with improved HIV treatment outcomes among people who use drugs (PWUD). The extent to which these benefits are sustained in the context of ongoing cocaine use is unclear. We assessed differential impacts of MMT on HIV viral load (VL) suppression in relation to discrete patterns of cocaine use.

METHODS

Data was drawn from ACCESS, a prospective cohort of HIV-positive PWUD in Vancouver, Canada. Generalized linear mixed-effects were used to model the independent effect of MMT on VL suppression across strata of frequency of cocaine injection and crack smoking (≥daily versus <daily), after adjustment for confounders.

RESULTS

The analysis included 397 HIV-positive opioid users who completed ≥1 study interview between 2005 and 2014. At baseline, 304 (77%) reported participation in MMT, 37 (9%) ≥daily cocaine injection, and 158 (40%) ≥daily crack smoking. In adjusted analyses, MMT remained independently associated with increased odds of VL suppression in both strata of crack smokers (AOR=3.11, 95% CI: 1.86-5.21 and AOR=1.48, 95%CI: 1.04-2.09, for ≥daily and <daily smokers, respectively), and among <daily cocaine injectors (AOR=1.88, 95%CI 1.38-2.56), but not among ≥daily cocaine injectors (AOR=1.37, 95%CI 0.53-3.49). Longer retention on MMT was positively associated with VL suppression in all strata of cocaine injection and crack smoke.

CONCLUSIONS

Exposure to MMT was associated with increased odds of VL suppression among HIV- positive opioid users regardless of crack use. However, this beneficial effect of MMT was lost among frequent cocaine injectors with shorter retention on MMT.

The role of living context in prescription opioid injection and the associated risk of hepatitis C infection

BACKGROUND AND AIMS

Prescription opioid injection (POI) is a leading risk factor for hepatitis C virus (HCV). Residential context relates to high‐risk injection behaviour. This study assessed whether residence in the inner city (versus surrounding areas in Montréal Island) modified the effects of correlates of POI or the relationship between POI and HCV incidence.

DESIGN

Prospective cohort study.

SETTING

Montréal, Canada.

PARTICIPANTS

A total of 854 people who inject drugs (18% female, 25% age < 30 years), living on Montréal Island, were interviewed every 3–6 months from 2004 to 2012.

MEASUREMENTS

Study visits included HCV antibody testing and an interviewer‐administered questionnaire. Generalized estimating equations were used to test whether place of residence modified the effects of correlates of POI. Cox regression was used to test whether place of residence modified the relationship between POI and HCV incidence.

FINDINGS

At baseline, inner‐city participants were more likely to report POI in the past month (40 versus 25%, P < 0.001). The association between POI and heroin injection, syringe sharing and sharing of injecting equipment varied according to place of residence and was greater in the inner city. The hazard of HCV infection associated with POI was greater among inner‐city participants compared to those in the surrounding areas [adjusted hazard ratio (HR) = 3.38, 95% confidence interval (CI) = 1.88–6.07 versus HR = 1.26, 95% CI = 0.65–2.42, P = 0.025].

CONCLUSIONS

Among people who inject prescription opioids in Montréal, Canada, those who live in inner‐city areas are more likely to engage in injecting‐related risk behaviours and have a higher risk of hepatitis C virus infection than those who live in the suburbs.

Factors associated with being asked to initiate someone into injection drug use

AIMS

Injection drug use initiation typically involves an established person who injects drugs (PWID) helping the injection-naïve person to inject. Prior to initiation, PWID may be involved in behaviors that elevate injection initiation risk for non-injectors such as describing how to inject and injecting in front of injection-naïve people. In this analysis, we examine whether PWID who engage in either of these behaviors are more likely to be asked to initiate someone into drug injection.

METHODS

Interviews with PWID (N = 602) were conducted in California between 2011 and 2013. Multivariate analysis was conducted to determine factors associated with being asked to initiate someone.

RESULTS

The sample was diverse in terms of age, race/ethnicity, and drug use patterns. Seventy-one percent of the sample had ever been asked to initiate someone. Being asked to initiate someone was associated with having injected in front of non-injectors (Adjusted Odds Ratio [AOR] = 1.80, 95% Confidence Interval [CI] = 1.12, 2.91), having described injection to non-injectors (AOR = 3.63; 95% CI = 2.07, 6.36), and doing both (AOR = 9.56; 95% CI = 4.43, 20.65) as compared to doing neither behavior (referent). Being female (AOR = 1.73; 95% CI = 1.10, 2.73) and non-injection prescription drug misuse in the last 30 days (AOR = 1.69; 95% CI = 1.12, 2.53) were also associated with having been asked to initiate someone.

CONCLUSION

Reducing initiation into injection drug use is an important public health goal. Intervention development to prevent injection initiation should include established PWID and focus on reducing behaviors associated with requests to initiate injection and reinforcing refusal skills and intentions among established PWID.

Factors associated with initiating someone into illicit drug injection

AIMS

Most people who inject drugs (PWID) were first initiated into injection by a current PWID. Few studies have examined PWID who assist others into drug injection. Our goal is to describe the prevalence of and risk factors for initiating someone into injection in the last 12 months.

METHODS

We recruited a cross-sectional sample of PWID (N=605) in California from 2011 to 2013. We examined bivariate and multivariate risk factors for initiating someone into injection with a focus on behaviors that might encourage injection initiation such as injecting in front of non-PWID, describing how to inject to non-PWID, and willingness to initiate someone into drug injection.

RESULTS

Having initiated someone into injection was reported by 34% of PWID overall and 7% in the last 12 months. Forty-four PWID had assisted 431 people into injection in the past year. Factors independently associated with initiating someone into injection in the last 12 months were self-reported likelihood of initiating someone in the future (Adjusted Odds Ratio [AOR]=7.09; 95% Confidence Interval [CI]=3.40, 14.79), having injected another PWID in past month (AOR=4.05; 95% confidence interval [CI]=1.94, 8.47), having described how to inject to non-injectors (2.61; 95% CI=1.19, 5.71), and non-injection powder cocaine use in past month (AOR=4.97; 95% CI=2.08, 11.84) while controlling for study site.

CONCLUSION

Active PWID are important in facilitating the process of drug injection uptake. Interventions to reduce initiation should include efforts to change behaviors and intentions among PWID that are associated with injection uptake among others.

The impact of engagement in street-based income generation activities on stimulant drug use cessation among people who inject drugs

BACKGROUND

Despite the growing prevalence of illicit stimulant drug use internationally, and the widespread involvement of people who inject drugs (IDU) within street-based drug markets, little is known about the impact of different types of street-based income generation activities on the cessation of stimulant use among IDU.

METHODS

Data were derived from an open prospective cohort of IDU in Vancouver, Canada. We used Kaplan-Meier methods and Cox proportional hazards regression to examine the effect of different types of street-based income generation activities (e.g., sex work, drug dealing, and scavenging) on time to cessation of stimulant use.

RESULTS

Between December, 2005 and November, 2012, 887 IDU who use stimulant drugs (cocaine, crack cocaine, or crystal methamphetamine) were prospectively followed-up for a median duration of 47 months. In Kaplan-Meier analyses, compared to those who did not engage in street-based income generation activities, participants who reported sex work, drug dealing, scavenging, or more than one of these activities were significantly less likely to report stimulant drug use cessation (all p<0.001). When considered as time-updated variables and adjusted for potential confounders in a multivariable model, each type of street-based income generation activity remained significantly associated with a slower time to stimulant drug cessation (all p<0.005).

CONCLUSIONS

Our findings highlight the urgent need for strategies to address stimulant dependence, including novel pharmacotherapies. Also important, structural interventions, such as low-threshold employment opportunities, availability of supportive housing, legal reforms regarding drug use, and evidence-based approaches that reduce harm among IDU are urgently required.

Cognitive performance profiles by latent classes of drug use

BACKGROUND AND OBJECTIVES

The relationship between substance use and cognitive deficits is complex and requires innovative methods to enhance understanding. The present study is the first to use LCA to examine associations of drug use patterns with cognitive performance.

METHODS

Cocaine/heroin users (N = 552) completed questionnaires, and cognitive measures. LCA identified classes based on past-month drug use and adjusted for probabilities of group membership when examining cognitive performance. Latent indicators were: alcohol (ALC), cigarettes (CIG), marijuana (MJ), crack smoking (CS), nasal heroin (NH), injection cocaine (IC), injection heroin (IH), and injection speedball (IS). Age and education were included as covariates in model creation.

RESULTS

Bootstrap likelihood ratio test (BLRT) supported a 5-class model. Prevalent indicators (estimated probability of over 50%) for each class are as follows: "Older Nasal Heroin/Crack Smokers" (ONH/CS, n = 166.9): ALC, CIG, NH, CS; "Older, Less Educated Polysubstance" (OLEP, n = 54.8): ALC, CIG, CS, IH, IC, and IS; "Younger Multi-Injectors" (MI, n = 128.7): ALC, CIG, MJ, IH, IC, and IS; "Less Educated Heroin Injectors" (LEHI, n = 87.4): CIG, IH; and "More Educated Nasal Heroin" users (MENH, n = ALC, CIG, NH. In general, all classes performed worse than established norms and older, less educated classes performed worse, with the exception that MENH demonstrated worse cognitive flexibility than YMI.

DISCUSSION AND CONCLUSIONS

This study demonstrated novel applications of a methodology for examining complicated relationships between polysubstance use and cognitive performance.

SCIENTIFIC SIGNIFICANCE

Education and/or nasal heroin use are associated with reduced cognitive flexibility in this sample of inner city drug users.

Binge Drug Use among Street-Involved Youth in a Canadian Setting

BACKGROUND

Binge drug use has been associated with increased risk of HIV infection and other serious health-related harms among adult drug user populations. This study sought to determine the prevalence and correlates of binge drug use among street-involved youth in a Canadian setting.

METHODS

From Sept 2005 to May 2012, data were collected from the At-Risk Youth Study (ARYS), a prospective cohort of street-involved youth aged 14 - 26 who use illicit drugs. Multivariate generalized estimating equations (GEE) was used to identify factors associated with binge drug use.

RESULTS

Of the 987 participants included in this analysis, 41.5% reported binge drug use at baseline, and another 59.1% reported binge drug use at some point during the study. In multivariate GEE analysis, older age (adjusted odds ratio [AOR] = 1.11), homelessness (AOR = 1.67), drug injecting (AOR = 1.63), non-fatal overdose (AOR = 1.98), public injecting (AOR 1.42), being a victim of violence (AOR = 1.38), sex work (AOR = 2.51) and participation in drug dealing (AOR = 2.04) were independently associated with binge drug use in the previous 6 months (all p<0.05).

DISCUSSION

The prevalence of reporting binge drug use among the youth was high in this setting and was independently associated with a range of high-risk activities and markers of vulnerability. Querying high-risk youth about binge drug use may help prioritize those in greatest need of addiction treatment strategies and public health interventions.

Stress modulates illness-course of substance use disorders: a translational review

Childhood trauma and post-childhood chronic/repeated stress could increase the risk of a substance use disorder by affecting five stages of addiction illness-course: (a) initial experimentation with substances; (b) shifting from experimental to regular use; (c) escalation from regular use to abuse or dependence; (d) motivation to quit; and (e) risk of (re-)lapse. We reviewed the human literature on relationships between stress and addiction illness-course. We explored per illness-course stage: (i) whether childhood trauma and post-childhood chronic/repeated stress have comparable effects and (ii) whether effects cut across classes of substances of abuse. We further discuss potential underlying mechanisms by which stressors may affect illness-course stages for which we relied on evidence from studies in animals and humans. Stress and substances of abuse both activate stress and dopaminergic motivation systems, and childhood trauma and post-childhood stressful events are more chronic and occur more frequently in people who use substances. Stressors increase risk to initiate early use potentially by affecting trait-like factors of risk-taking, decision making, and behavioral control. Stressors also accelerate transition to regular use potentially due to prior effects of stress on sensitization of dopaminergic motivation systems, cross-sensitizing with substances of abuse, especially in people with high trait impulsivity who are more prone to sensitization. Finally, stressors increase risk for abuse and dependence, attenuate motivation to quit, and increase relapse risk potentially by intensified sensitization of motivational systems, by a shift from positive to negative reinforcement due to sensitization of the amygdala by corticotropin releasing factor, and by increased sensitization of noradrenergic systems. Stress generally affects addiction illness-course across stressor types and across classes of substances of abuse.

Consumo de sustancias psicoactivas en dos regiones argentinas y su relación con indicadores de pobreza

Se realizó un análisis de base de datos recolectados en la Encuesta Nacional de Prevalencia de Consumo de Sustancias Psicoactivas (ENPreCoSP-2.008) tomando 6.122 casos, con los objetivos de describir las prevalencias de consumo de sustancias psicoactivas; y evaluar la asociación entre la existencia de necesidades básicas insatisfechas y el nivel de ingresos familiares, con el consumo de sustancias psicoactivas en personas entre las edades de 18 a 34 años, residentes en las regiones noroeste (NOA) y noreste (NEA) argentino. Se realizaron análisis descriptivos y regresión logística. Las prevalencias de consumo en la vida, el último año y el último mes fueron mayores en sustancias legales. Así también, el consumo fue mayor en el sexo masculino. Los indicadores de situación de pobreza operaron como factor de riesgo para el consumo de sustancias legales. Los resultados encontrados dan cuenta de situaciones diferenciales en el consumo de sustancias psicoactivas, en relación al género y a las condiciones de pobreza.

Multiple routes of drug administration and HIV risk among injecting drug users

This study assesses relationships between drug administration routes and HIV serostatus, drug use, and sexual behaviors among current injecting drug users (IDUs) in Tallinn, Estonia. We recruited 350 IDUs for a cross-sectional risk behavior survey. Adjusted odds ratios (AORs) were calculated to explore injection risk behavior, sexual behavior, and HIV serostatus associated with multiple route use. Focus groups explored reasons why injectors might use non-injecting routes of administration. Those reporting multiple drug administration routes were less likely to be HIV seropositive (AOR = 0.49, 95% confidence interval [CI] = 0.25-0.97) and had almost twice the odds of having more than one sexual partner (AOR = 1.90, 95% CI = 1.01-3.60) and of reporting having sexually transmitted diseases (AOR = 2.38, 95% CI = 1.02-5.59). IDUs who engage in noninjecting drug use may be reducing their risk of acquiring HIV though sharing injection equipment, but if infected may be a critical group for sexual transmission of HIV to people who do not inject drugs.

Understanding subtypes of inner-city drug users with a latent class approach

AIMS

We empirically identified subtypes of inner-city users of heroin and cocaine based on type of drug used and route of administration.

METHOD

The sample was recruited from the communities in Baltimore, MD (SHIELD study) and consisted of 1061 participants who used heroin and or cocaine in the past 6 months on a weekly basis or more. Latent class analysis (LCA) was used to identify subtypes of drug users based on type of drug and route of administration. Logistic regression was used to compare the subtypes on depressive symptoms, injection risk and drug network compositions.

FINDINGS

Inner-city drug users were classified into five subtypes: three subtypes of injection drug users (IDUs) [heroin injecting (n=134; 13%), polydrug and polyroute (n=88, 8%), and heroin and cocaine injecting (n=404, 38%)], and two subtypes with low proportions of IDUs (LIDUs) [heroin snorting (n=275, 26%) and crack smoking (n=160; 14%)]. The polydrug and polyroute subtype had the highest depressive symptoms risk among all subtypes. Injection risk was lowest in the heroin injecting subtype and significantly differed from heroin and cocaine injecting subtype. The IDU subtypes also varied in the drug network compositions. The LIDU subtypes had similar depressive symptoms risk but vastly differed in the drug network compositions.

CONCLUSIONS

Subgroups of inner-city cocaine and heroin users based on type and route of administration differed in their depressive symptoms, injection risk and drug network compositions. Future studies should longitudinally examine factors associated with transitioning across these subtypes to better inform prevention and treatment efforts.

Reduction in overdose mortality after the opening of North America's first medically supervised safer injecting facility: a retrospective population-based study

BACKGROUND

Overdose from illicit drugs is a leading cause of premature mortality in North America. Internationally, more than 65 supervised injecting facilities (SIFs), where drug users can inject pre-obtained illicit drugs, have been opened as part of various strategies to reduce the harms associated with drug use. We sought to determine whether the opening of an SIF in Vancouver, BC, Canada, was associated with a reduction in overdose mortality.

METHODS

We examined population-based overdose mortality rates for the period before (Jan 1, 2001, to Sept 20, 2003) and after (Sept 21, 2003, to Dec 31, 2005) the opening of the Vancouver SIF. The location of death was determined from provincial coroner records. We compared overdose fatality rates within an a priori specified 500 m radius of the SIF and for the rest of the city.

FINDINGS

Of 290 decedents, 229 (79·0%) were male, and the median age at death was 40 years (IQR 32-48 years). A third (89, 30·7%) of deaths occurred in city blocks within 500 m of the SIF. The fatal overdose rate in this area decreased by 35·0% after the opening of the SIF, from 253·8 to 165·1 deaths per 100,000 person-years (p=0·048). By contrast, during the same period, the fatal overdose rate in the rest of the city decreased by only 9·3%, from 7·6 to 6·9 deaths per 100,000 person-years (p=0·490). There was a significant interaction of rate differences across strata (p=0·049).

INTERPRETATION

SIFs should be considered where injection drug use is prevalent, particularly in areas with high densities of overdose.

FUNDING

Vancouver Coastal Health, Canadian Institutes of Health Research, and the Michael Smith Foundation for Health Research.

Transition to and from injecting drug use among regular ecstasy users

There is a scant amount of research investigating injecting drug use among people not selected on the basis of their injecting behaviour, and less attention has been given to stimulant users who may have a different experience with injecting drug use than opioid users who are more commonly studied. The current study aimed to investigate initiation to, and transition from, injecting drug use among a sentinel sample of regular ecstasy users in Australia. Participants were regular ecstasy users recruited across Australia in 2007 who were administered a structured interview that contained questions regarding initiation to injecting, reasons for injecting cessation, and likelihood of future injecting. Among those with a history of injecting drug use, injecting first occurred at a similar age to that of first ecstasy use. The majority did not inject themselves at the first occasion, and two-fifths were under the influence of other drugs at the time. Two-fifths of injectors had not injected in the past 6 months, with many relating this to concerns surrounding stigma. Route of drug administration is clearly not static, and the findings from this study suggest that some who have ceased injecting may still be at risk for future injecting.

Composition, purity and perceived quality of street cocaine in France

BACKGROUND

There is little knowledge about the composition and cocaine content of street cocaine, nor about what users know about it.

METHOD

373 cocaine users were face to face interviewed between May and December 2006 about the last sample of cocaine they had consumed and residual amounts of the substances actually used were analysed using gas phase chromatography coupled to mass spectrometry (GC-MS). Users rated the perceived quality of their product ("good", "average", "poor"), its "estimated percentage of cocaine" and any cutting agents it contained. Price, quantity, place of purchase (street, dealer's premise, appointment), mode of administration (sniffing, injection, smoking) and the supposed nature of the sample (natural, synthetic, no distinction ever made) were also reported. Perceived quality was modelled using multivariate multinomial regression.

RESULTS

The median cocaine content was 22%. Altogether, 343 samples contained cocaine, among which 75% contained at least one adulterant. The most frequently occurring were phenacetin (54% of the samples), caffeine (17%), paracetamol (14%), diltiazem and lidocaïne (11%). Users showed relatively poor discrimination concerning cocaine purity, and only 12% reported at least one of the detected adulterants. The major determinants of their perception of cocaine quality were: place of purchase, natural origin, price per gram, actual cocaine content and mode of administration.

CONCLUSION

The composition of street cocaine is largely unknown to users. Users' perceptions of cocaine quality are based partly on false beliefs and certain administration modes. This may contribute to favouring very risky practices. The effects of adulterants on users' health should be investigated.

Assisted injection in outdoor venues: an observational study of risks and implications for service delivery and harm reduction programming

BACKGROUND

Assisted injection and public injection have both been associated with a variety of individual harms including an increased risk of HIV infection. As a means of informing local IDU-driven interventions that target or seek to address assisted injection, we examined the correlates of receiving assistance with injecting in outdoor settings among a cohort of persons who inject drugs (IDU).

METHODS

Using data from the Vancouver Injection Drug Users Study (VIDUS), an observational cohort study of IDU, generalized estimating equations (GEE) were performed to examine socio-demographic and behavioural factors associated with reports of receiving assistance with injecting in outdoor settings.

RESULTS

From January 2004 to December 2005, a total of 620 participants were eligible for the present analysis. Our study included 251 (40.5%) women and 203 (32.7%) self-identified Aboriginal participants. The proportion of participants who reported assisted injection outdoors ranged over time between 8% and 15%. Assisted injection outdoors was independently and positively associated with being female (Adjusted Odds Ratio (AOR) = 1.74, 95% Confidence Intervals (CI): 1.21-2.50), daily cocaine injection (AOR = 1.70, 95% CI: 1.29-2.24), and sex trade involvement (AOR = 1.44, 95% CI: 1.00-2.06) and was negatively associated with Aboriginal ethnicity (AOR = 0.58, 95% CI: 0.41-0.82).

CONCLUSIONS

Our findings indicate that a substantial proportion of local IDU engage in assisted injecting in outdoor settings and that the practice is associated with other markers of drug-related harm, including being female, daily cocaine injecting and sex trade involvement. These findings suggest that novel interventions are needed to address the needs of this subpopulation of IDU.

Community-associated methicillin-resistant Staphylococcus aureus is prevalent in wounds of community-based injection drug users

Injection drug users (IDUs) have an elevated risk for carriage of Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA). Cutaneous injection-related infections are common in IDUs but detailed studies are few. Based on a subsample of 218 individuals from a community-recruited cohort of IDUs at a supervised injection facility, we investigated the microbiology and related antibiotic susceptibility profiles of isolates from 59 wounds. Twenty-seven percent of subjects had at least one wound and 25 (43%) were culture positive for S. aureus alone [14 MRSA and 11 (19%) methicillin-susceptible (MSSA) isolates]. Sixteen of 18 MRSA isolates were classified as community associated (CA) by the presence of genes encoding for PVL. MRSA and MSSA occurred in mixed infection with other organisms on three and six occasions, respectively. All CA-MRSA isolates were susceptible to tetracycline, vancomycin and linezolid but only 13% were susceptible to clindamycin compared to 63% of MSSA isolates. The frequency of CA-MRSA is a cause for concern in wound infection in the IDU setting.

THE FIRST INJECTION EVENT: DIFFERENCES AMONG HEROIN, METHAMPHETAMINE, COCAINE, AND KETAMINE INITIATES

This article describes how the drug type injected at the first injection event is related to characteristics of the initiate, risk behaviors at initiation, and future drug-using trajectories. A diverse sample (n=222) of young injection drug users (IDUs) were recruited from public settings in New York, New Orleans, and Los Angeles during 2004 and 2005. The sample was between 16 and 29 years old, and had injected ketamine at least once in the preceding two years. Interview data was analyzed both quantitatively and qualitatively. Young IDUs initiated with four primary drug types: heroin (48.6%), methamphetamine (20.3%), ketamine (17.1%), and cocaine (14%). Several variables evidenced statistically significant relationships with drug type: age at injection initiation, level of education, region of initiation, setting, mode of administration, patterns of self-injection, number of drugs ever injected, current housing status, and their hepatitis C virus (HCV) status. Qualitative analyses revealed that rationale for injection initiation and subjective experiences at first injection differed by drug type.