Faculty Bibliography

Agent-based modeling is a computational approach in which agents with a specified set of characteristics interact with each other and with their environment according to predefined rules. We review key areas in public health where agent-based modeling has been adopted, including both communicable and noncommunicable disease, health behaviors, and social epidemiology. We also describe the main strengths and limitations of this approach for questions with public health relevance. Finally, we describe both methodologic and substantive future directions that we believe will enhance the value of agent-based modeling for public health. In particular, advances in model validation, comparisons with other causal modeling procedures, and the expansion of the models to consider comorbidity and joint influences more systematically will improve the utility of this approach to inform public health research, practice, and policy.

Alcohol and marijuana are two of the most prevalent psychoactive substances and each may result in distinct psychosocial and physical sexual experiences and different sexual risk behaviors. With marijuana becoming more accepted in the US along with more liberal state-level policies, it is important to examine and compare users' psychosocial and physical sexual experiences and sexual risk behavior associated with these drugs. In this study, we interviewed 24 adults who recently used marijuana before sex. Participants were 50 % female and all self-identified as heterosexual and HIV-negative. Using thematic analysis, we compared self-reported psychosocial and physical sexual experiences of alcohol and marijuana. Participants described differences between drugs with regard to psychosocial (e.g., partner interactions and contexts before sex, partner choice, perceived attractiveness of self and others, disinhibition, and feelings of regret after sex) and physical sexual experiences (e.g., sexual dysfunction, dose effects, sensations of body/sex organs, length and intensity of sex, and orgasm). Alcohol use was commonly associated with social outgoingness and use facilitated connections with potential sexual partners; however, alcohol was more likely than marijuana to lead to atypical partner choice or post-sex regret. Both alcohol and marijuana had a variety of negative sexual effects, and the illegality of marijuana reportedly facilitated intimate encounters. While sexual experiences tended to be similar across males and females, we did find some variation by gender. Results can inform prevention and harm reduction programming that will allow us to design more realistic programs and to craft interventions, which guide potential users to make safer choices.

BACKGROUND:Associations have been observed between an aggregate viral load measure, the community viral load, and new HIV diagnoses. The community viral load aggregates viral loads within chosen geographic areas, restricting inferences about HIV acquisition risk to these areas. We develop a more precise metric, the network viral load (NVL), to measure the composite viral load within a risk network of a HIV-negative individual. METHODS:We examined the relationship between NVL and HIV infection among young men who have sex with men in Chicago, United States. Networks were generated using respondent-driven sampling. NVL was defined as the prevalence of viremic individuals in one's risk network, characterized as those with a viral load ≥20 k copies per milliliter. Permutation tests were conducted to account for dependency. RESULTS:After controlling for total connections, age, substance use during sex, syphilis diagnosis (previous 12 months), and frequency of condomless anal sex (previous 6 months), we found a positive association between NVL and HIV infection. Compared with a network with all HIV-seronegative members, the odds of HIV infection with an NVL of <10% viremia were 1.85 (95% confidence interval: 1.18 to 2.92) times higher and those with an NVL of ≥10% viremia were 2.73 (95% confidence interval: 1.54 to 4.85) times higher. CONCLUSIONS:We found a positive association between NVL and HIV seroprevalence. Although limited in its ability to infer causality, NVL could have substantial public health implications for persons most at risk for HIV infection, given that this novel metric avoids overreliance on individual level behavior or broad community indices.

BACKGROUND:Most recent research on adolescent drug use has focused on alcohol, tobacco, and marijuana. Less is known about the recent epidemiology of adolescent cocaine use, which has serious health consequences. PURPOSE:To describe recent trends in cocaine use by U.S. high school students, and identify differences in lifetime and repeated use across sex and racial/ethnic groups. METHODS:We used data from the national Youth Risk Behavior Surveys (YRBS) from 1999 to 2015. We estimated the prevalence of lifetime cocaine use (LCU) and repeated lifetime cocaine use (RLCU) across years by race/ethnicity and sex and tested for linear and quadratic trends. RESULTS:The prevalence of LCU decreased from 1999 to 2015 (9.54%-5.19%). RLCU also decreased (5.13%-2.84%). Despite the overall decline, LCU and RLCU both rose between 2009-2015 (LCU:2.78%-5.19%, RLCU:1.58%-2.84%). Boys had higher rates of LCU and RLCU than girls (LCU:6.42% vs 4.65%; RLCU:3.69% vs 2.18%). American Indian/Alaskan Native, Native Hawaiian/Pacific Islander, and Hispanic adolescents had the highest overall prevalence of LCU. Black adolescents' LCU patterns differed from other racial/ethnic groups. The prevalence of LCU among Black boys increased over time, while the prevalence for Black girls remained consistently low. CONCLUSIONS:Adolescent cocaine use is less common today than in the 1990s. However, rates of adolescent cocaine use have risen across all racial/ethnic groups in the past few years. Public health efforts should address at risk groups with particularly high or rising rates of cocaine use.

BACKGROUND:Historical shifts have taken place in the last twenty years in marijuana policy. The impact of medical marijuana laws (MML) on use of substances other than marijuana is not well understood. We examined the relationship between state MML and use of marijuana, cigarettes, illicit drugs, nonmedical use of prescription opioids, amphetamines, and tranquilizers, as well as binge drinking. METHODS:Pre-post MML difference-in-difference analyses were performed on a nationally representative sample of adolescents in 48 contiguous U.S. states. Participants were 1,179,372U.S. 8th, 10th, and 12th graders in the national Monitoring the Future annual surveys conducted in 1991-2015. Measurements were any self-reported past-30-day use of marijuana, cigarettes, non-medical use of opioids, amphetamines and tranquilizers, other illicit substances, and any past-two-week binge drinking (5+ drinks per occasion). RESULTS:Among 8th graders, the prevalence of marijuana, binge drinking, cigarette use, non-medical use of opioids, amphetamines and tranquilizers, and any non-marijuana illicit drug use decreased after MML enactment (0.2-2.4% decrease; p-values:<0.0001-0.0293). Among 10th graders, the prevalence of substance use did not change after MML enactment (p-values: 0.177-0.938). Among 12th graders, non-medical prescription opioid and cigarette use increased after MML enactment (0.9-2.7% increase; p-values: <0.0001-0.0026). CONCLUSIONS:MML enactment is associated with decreases in marijuana and other drugs in early adolescence in those states. Mechanisms that explain the increase in non-medical prescription opioid and cigarette use among 12th graders following MML enactment deserve further study.

"10:10 a.m., September 11, 2001" -- "Becoming an 'Other'" -- "Remember" -- "Little things"

Firearm violence frequently involves alcohol, but there are no studies of misuse of alcohol and risk for future violence among firearm owners. We examined the association between prior convictions for alcohol-related crimes, chiefly driving under the influence (DUI), and risk of subsequent arrest among 4066 individuals who purchased handguns in California in 1977. During follow-up through 1991, 32.8% of those with prior alcohol-related convictions and 5.7% of those with no prior criminal history were arrested for a violent or firearm-related crime; 15.9% and 2.7%, respectively, were arrested for murder, rape, robbery or aggravated assault. Prior alcohol-related convictions were associated with a fourfold to fivefold increase in risk of incident arrest for a violent or firearm-related crime, a relative increase greater than that seen for age, sex or prior violence. Prior convictions for alcohol-related crime may be an important predictor of risk for future criminal activity among purchasers of firearms.

INTRODUCTION AND AIMS/OBJECTIVE:Given a scenario of intense discussion about the legal situation of cannabis users worldwide, this paper aims to investigate the role of cannabis within a drug use sequencing pattern. DESIGN AND METHODS/METHODS:Data came from a representative sample of college students from 27 Brazilian capitals (n = 12 711). We analysed the patterns of transition from/to the first use of cannabis to/from the first use of alcohol, tobacco and seven other illegal drugs. Survival analysis methods were used to analyse age of onset data on all potential drug pairs. Drugs that were not specified as the target drug pair tested in each survival model were included as time-varying covariates in all models. RESULTS:We found significant transitions from alcohol [adjusted hazard ratio (aHR) = 1.41, 95% confidence interval (CI) 1.15-1.73, P < 0.001] and inhalants (aHR = 1.56, 95% CI 1.26-1.93, P < 0.001) to cannabis. Moreover, we found significant transitions from cannabis to alcohol (aHR = 2.40, 95% CI 1.47-3.91, P < 0.001), cocaine (aHR = 7.47, 95% CI = 4.26-13.09, P < 0.001), prescription opioids (aHR = 2.16, 95% CI 1.29-3.63, P < 0.01) and tranquilisers (aHR = 1.51, 95% CI 1.11-2.06, P < 0.01). DISCUSSION AND CONCLUSIONS/CONCLUSIONS:Overall, our findings point to a strategic role of cannabis within drug first use sequence pattern. We had an important and unexpected finding-the bi-directional relationship between alcohol and cannabis. In addition, the first use of cannabis still precedes the first use of cocaine and non-medical use of tranquilisers and prescription opioids. [Castaldelli-Maia JM, Nicastri S, Cerdá M, Kim JH, Oliveira LG, Andrade AG, Martins, SS. In-transition culture of experimentation with cannabis in Latin American college students: A new role within a potential drug use sequencing pattern. Drug Alcohol Rev 2017;00:000-000].

Ukraine has one of the largest HIV epidemics in Europe, historically driven by people who inject drugs (PWID). The epidemic showed signs of stabilization in 2012, but the recent war in eastern Ukraine may be reigniting virus spread. We investigated the movement of HIV-infected people within Ukraine before and during the conflict. We analyzed HIV-1 subtype-A pol nucleotide sequences sampled during 2012-2015 from 427 patients of 24 regional AIDS centers and used phylogeographic analysis to reconstruct virus movement among different locations in Ukraine. We then tested for correlations between reported PWID behaviors and reconstructed patterns of virus spread. Our analyses suggest that Donetsk and Lugansk, two cities not controlled by the Ukrainian government in eastern Ukraine, were significant exporters of the virus to the rest of the country. Additional analyses showed that viral dissemination within the country changed after 2013. Spearman correlation analysis showed that incoming virus flow was correlated with the number of HIV-infected internally displaced people. Additionally, there was a correlation between more intensive virus movement and locations with a higher proportion of PWID practicing risky sexual behaviors. Our findings suggest that effective prevention responses should involve internally displaced people and people who frequently travel to war-affected regions. Scale-up of harm reduction services for PWID will be an important factor in preventing new local HIV outbreaks in Ukraine.