Differing approaches to risk reduction needed for cocaine or heroin injectors

A study of injection drug users in Montreal has found significant differences between cocaine and heroin users, not only in personal and drug-taking behaviours, but between their social and drug-using networks as well, suggesting that prevention efforts could be tailored to address these differences. The study was published in the November 1^st edition of the Journal of Acquired Immune Deficiency Syndromes.

Many behaviour patterns in injection drug users (IDUs) depend greatly on their drug of choice. Those who predominantly use heroin, an opiate with a long-lasting "high", tend to inject less frequently but more regularly over the long term. In contrast, IDUs who use cocaine (a short-acting stimulant) are much more likely to inject frequently, take part in "binge" use, share needles, and live more chaotic and socially disadvantaged lives. Among IDUs, cocaine users are at greater risk for contracting HIV, hepatitis C virus (HCV) and other blood-borne diseases.

These differences in IDU drug-using behaviours of IDUs have been well-established by previous research. The objective of the current study was to further explore the social networks of IDUs – the characteristics of the people with whom they interact socially and in shared drug-taking, and the ways in which those interactions vary. This was a cross-sectional study of actively drug-using adults who had injected drugs at least once in the past six months, recruited from three large syringe exchange programs and two methadone clinics in Montréal, Canada between April 2004 and January 2005.

The relatively few (14) initially recruited participants who reporting speedballing (regularly using a mixture of cocaine and heroin) were excluded from analysis, leaving a sample of 282 participants who predominantly used one drug or the other (half the time or more). Most people in this sample (83%) were accessed via syringe exchange programs. Participants from methadone clinics had to have recently begun treatment; other studies have indicated that injection and risk behaviours may change only minimally shortly after methadone treatment is begun. Participants' mean age was 33 years, 73% were male, 90% were white, 88% were single, and 42% lived in unstable housing conditions. By self-report, 19% were HIV-positive (only), 64% were HCV-positive (only), and 19% were co-infected.

Of these 282, 228 (81%) used cocaine as their primary drug and 54 (19%) used heroin. Cocaine users were more likely to be men (77% vs. 57%, p = 0.004), be unstably housed (47% vs. 21%, p

Social contacts were defined as people with whom the participants had had significant contact with in the past month, in which the contact person had played an important role in the participant's life. Contacts were classified into three categories: IDU (drug dealers and drug-sharing partners), sexual (partners and clients), and socially supportive roles (including friends, co-workers, and family members). The categories were not mutually exclusive. Participants then provided information about the people who they had (anonymously) named as their social contacts.

Cocaine users had slightly larger networks (mean 4.22 vs. 3.30, p

The authors suggest that larger socially supportive networks may be more likely to encourage harm reduction, while larger networks of drug-using peers are more likely to encourage risky injecting. In this study, "the size of the social support network seemed to be less important than the mere presence of social support": having any socially supportive contacts was associated with lower risk behaviour than for those who had none. The size of IDU networks, conversely, appeared to matter: larger risks were associated with larger numbers of IDU contacts rather than simply a nonzero number.

The investigators note that the study was cross-sectional, that multiple drug use may obscure the either-or distinction between drugs of choice, and that respondent-reported characteristics of their peer networks may have been limited in accuracy. However, they conclude that their findings "stress the importance of considering risk influences beyond those of individual IDUs." They suggest that heroin-using IDUs "more easily formed networks though which harm reduction behaviours could be transmitted", while "interventions for cocaine injectors could require alternate strategies such as individually based education".