Perceived Treatment Need and Latent Transitions in Heroin and Methamphetamine Polydrug Use among People who Inject Drugs in Tijuana, Mexico

ABSTRACT

People who inject drugs (PWID) in Tijuana, Mexico, use heroin and/or methamphetamine. While polydrug use is associated with HIV risk behavior, less is known about the stability of polydrug use patterns over time and how polydrug use is related to perceived treatment need. Within a cohort of PWID in Tijuana (N = 735) we sought to (1) characterize subgroups of polydrug and polyroute use from baseline to six months; (2) determine the probabilities of transitioning between subgroups; and (3) examine whether self-reported need for help for drug use modified these transition probabilities. Latent transition analysis (LTA) identified four latent statuses: heroin-only injection (38% at both baseline and follow-up); co-injection of heroin with methamphetamine (3% baseline, 15% follow-up); injection of heroin and methamphetamine (37% baseline, 32% follow-up); and polydrug and polyroute users who injected heroin and both smoked and injected methamphetamine (22% baseline, 14% follow-up). Heroin-only injectors had the highest probability of remaining in the same latent status at follow-up. The majority reported great or urgent need for treatment (51%) and these PWID had greater odds of transitioning to a higher-risk status at follow-up, emphasizing the need for evidence-based drug treatment options for PWID.

KEYWORDS:

• Heroin
• latent transition analysis
• methamphetamine
• people who inject drugs
• polydrug
• route of administration

Acknowledgments

The authors gratefully acknowledge the contributions to this research by the study participants and staff.

Funding

This research is funded by the National Institutes of Health grant R37 DA019829; M.M. was supported by T32 DA023356 and T32 DA007250, and T.G. was supported by K01 DA034523.