Background : In Baja California, Mexico, high risk populations of male clients of female sex workers (FSWs) are at risk for acquiring HIV and experiencing harms related to substance use, while residents of rural communities are susceptible to the harms of drug-related gang violence. Nevertheless, factors related to HIV- related risk behavior, drug use, and gang violence remain under-studied in these vulnerable populations. Aims : The aims of this dissertation were : (1) to examine two methods of measuring unprotected sex among male clients of female sex workers in Tijuana, Mexico; (2) to examine the correlates of self-efficacy for condom use among male clients of female sex workers in Tijuana, Mexico; and (3) to examine the association between drug-scene familiarity and exposure to gang violence among residents in a rural farming community in Baja California, Mexico. Methods : In Chapter 2, 394 male clients of FSWs in Tijuana, Mexico were interviewed, and the results of measuring unprotected sex using dichotomous and count dependent variable approaches were compared. Chapter 3 examined quantitative survey data from Tijuana to identify socio-cognitive factors associated with self efficacy for condom use among 393 male clients. In Chapter 4, 169 residents in a small, rural community in Baja California completed surveys collecting information on drugs and gang violence. Results : In Chapter 2, the results of modeling the two analytic approaches measuring unprotected sex among male clients of FSWs showed that each approach identified several unique correlates that were not identified by the other. Chapter 3 identified psychosocial and psychosexual factors that may influence self-efficacy for condom use among male clients of FSWs. Chapter 4 found that exposure to gang violence was common and was associated with drug scene familiarity, suggesting a close relationship between drugs and gang violence in this community. Conclusions : Results from these preliminary analyses have important implications for the development of interventions to increase self-efficacy for condom use in order to influence safer sex among male clients of FSWs in Tijuana, and for interventions to prevent drug- and violence- related harms in rural communities in Baja California

Abstract Objective To assess factors associated with drug-related harms related to policing among injection drug users (IDUs) in Tijuana, Mexico. Methods IDUs who were over 18 years old and had injected drugs within the last six months were recruited via respondent-driven sampling and underwent questionnaires and testing for HIV (human immunodeficiency virus), syphilis and TB (tuberculosis). Random effects logistic regression was used to simultaneously model factors associated with five drug-related harms related to policing practices in the prior six months (i.e., police led them to rush injections; affected where they bought drugs; affected locations where they used drugs; feared that police will interfere with their drug use; receptive syringe sharing). Results Of 727 IDUs, 85% were male; median age was 38 years. Within the last 6 months, 231 (32%) of IDUs reported that police had led them to rush injections, affected where they bought or used drugs or were very afraid police would interfere with their drug use, or shared syringes. Factors independently associated with drug-related harms related to policing within the last six months included: recent arrest, homelessness, higher frequencies of drug injection, use of methamphetamine, using the local needle exchange program and perceiving a decrease in the purity of at least one drug. Conclusions IDUs who experienced drug-related harms related to policing were those who were most affected by other micro and macro influences in the physical risk environment. Police education programs are needed to ensure that policing practices do not exacerbate risky behaviors or discourage protective behaviors such as needle exchange program use, which undermines the right to health for people who inject drugs.

We examined correlates of ever injecting drugs in Mexico among residents of San Diego, California. From 2007 to 2010, injecting drug users (IDUs) in San Diego underwent an interviewer-administered survey. Logistic regression identified correlates of injection drug use in Mexico. Of 302 IDUs, 38% were Hispanic, 72% male and median age was 37; 27% ever injected in Mexico; 43% reported distributive syringe sharing there. Factors independently associated with ever injecting drugs in Mexico included being younger at first injection, injecting heroin, distributive syringe sharing at least half of the time, and transporting drugs over the last 6 months. One-quarter of IDUs reported ever injecting drugs in Mexico, among whom syringe sharing was common, suggesting possible mixing between IDUs in the Mexico-US border region. Prospective studies should monitor trends in cross-border drug use in light of recent Mexican drug policy reforms partially decriminalizing drug possession.