The Transmission of Gun and Other Weapon-Involved Violence Within Social Networks

Community exposure to gun homicide and adolescents' educational aspirations

INTRODUCTION

Witnessing violence and violent victimization have detrimental effects on adolescents' emotional functioning and ability to envision and plan for their futures. However, research is limited on the impact of violence that occurs in adolescents' communities-whether or not it was witnessed or experienced firsthand. This paper investigated the associations between community exposure to gun homicide and adolescents' high school and college graduation aspirations.

METHODS

We analyzed data from the Future of Families and Child Wellbeing Study (N = 3031), a cohort study of children born 1998-2000 in 20 large US cities, merged with incident-level data on deadly gun violence from the Gun Violence Archive (2014-2017). Outcomes were reported by adolescents (girls and boys) during wave 6 (2014-2017) of the study, conducted when the children were 15 years of age. We employed ordinary least squares regression, ordered logistic regression, and multilevel stratification to examine the average and heterogeneous impacts of community exposure to gun homicide on adolescents' educational aspirations.

RESULTS

Community exposure to gun homicide was associated with reduced high school graduation aspirations, particularly among adolescents with the lowest risk of exposure to gun homicide. Gun homicide exposure was also associated with increased college graduation aspirations; this association was concentrated among adolescents with moderate-high risk of exposure.

CONCLUSIONS

Given the importance of education for job opportunities and the better health that accompanies education and occupational attainment, preventing early exposure to gun violence and providing institutional supports to help adolescents facing adversity realize their goals is essential to their long-term health and success.

Costs of Summer Youth Employment to Prevent Violence: an Analysis and Implementer's Tool

Gun homicide rates have risen 35% across the USA since the start of the COVID-19 pandemic. One promising intervention to prevent violent crime is summer youth employment programs (SYEPs), which provide youth with meaningful workplace experiences, prosocial engagements, and developmental opportunities during the summer months, when many otherwise lack structure. This paper presents a cost analysis of violence prevention-focused SYEPs to help implementers understand the costs generally and in their own community contexts-to advocate for adoption and secure funding of, effectively budget for, and successfully implement SYEPs. Researchers use an ingredient-based costing approach and provide a template for implementers to use and adapt for their context. SYEPs with the goal of reaching youth who are justice-involved or at risk of being victims or perpetrators of violence can cost $3331 per youth assisted, with 54% of this cost directly paid to youth through stipends. Cost per youth is driven by the intensity of the mentoring and support that community organizations provide to the program participants. Knowing the cost per youth assisted can inform further analysis, implementation, and expansion of SYEPs.

Using social network analysis to examine gun violence

Research has found gun violence is a social contagion that spreads from one individual to another. To understand the social networks of violence, previous research has used social network analysis, a tool that explores the relationships between social actors. Most of the prior research uses coarrest data and incident reports to produce social networks. The current study incorporates the use of an underused data source, ballistic evidence, to better understand gun violence. The aim was to identify drivers of gun violence and to examine network concentration. Specifically, National Integrated Ballistic Information Network (NIBIN) leads and associated criminal incidents in combination with all incident reports were collected from a large urban county in the Pacific Northwest between 2015 and 2017. Social network analysis was conducted to produce a NIBIN network to demonstrate the connections between incidents where the same firearm was used. Social network analysis was also conducted to identify individuals who were the most involved in gun violence. Results reveal gun violence is very interconnected as many of the same firearms were discharged in multiple different incidents with several other individuals involved, indicating a connection between these individuals. This demonstrates the utility of using ballistic evidence beyond using only incident and coarrest data because it provides more information that directly relates to gun violence and the transfer of guns. Additionally, this can be very useful for law enforcement agencies to identify who is integral in the gun violence networks that can be helpful for prevention and intervention strategies.

Would restricting firearm purchases due to alcohol- and drug-related misdemeanor offenses reduce firearm homicide and suicide? An agent-based simulation

Background

Substance-related interactions with the criminal justice system are a potential touchpoint to identify people at risk for firearm violence. We used an agent-based model to simulate the change in firearm violence after disqualifying people from owning a firearm given prior alcohol- and drug-related misdemeanors.

Methods

We created a population of 800,000 agents reflecting a 15% sample of the adult New York City population.

Results

Disqualification from purchasing firearms for 5 years after an alcohol-related misdemeanor conviction reduced population-level rates of firearm homicide by 1.0% [95% CI 0.4–1.6%] and suicide by 3.0% [95% CI 1.9–4.0%]. Disqualification based on a drug-related misdemeanor conviction reduced homicide by 1.6% [95% CI 1.1–2.2%] and suicide by 4.6% [95% CI 3.4–5.8%]. Reductions were generally 2 to 8 times larger for agents meeting the disqualification criteria.

Conclusions

Denying firearm access based on a history of drug and alcohol misdemeanors may reduce firearm violence among the high-risk group. Enactment of substance use-related firearms denial criteria needs to be balanced against concerns about introducing new sources of disenfranchisement among already vulnerable populations.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40621-022-00381-x.

Simulating the bounds of plausibility: Estimating the impact of high-risk versus population-based approaches to prevent firearm injury

BACKGROUND

Firearm violence remains a persistent public health threat. Comparing the impact of targeted high-risk versus population-based approaches to prevention may point to efficient and efficacious interventions. We used agent-based modeling to conduct a hypothetical experiment contrasting the impact of high-risk (disqualification) and population-based (price increase) approaches on firearm homicide in New York City (NYC).

METHODS

We simulated 800,000 agents reflecting a 15% sample of the adult population of NYC. Three groups were considered and disqualified from all firearm ownership for five years, grouped based on prevalence: low prevalence (psychiatric hospitalization, alcohol-related misdemeanor and felony convictions, 0.23%); moderate prevalence (drug misdemeanor convictions, domestic violence restraining orders, 1.03%); and high prevalence (all other felony/misdemeanor convictions, 2.30%). Population-level firearm ownership was impacted by increasing the price of firearms, assuming 1% price elasticity.

RESULTS

In this hypothetical scenario, to reduce firearm homicide by 5% in NYC, 25% of the moderate prevalence group, or 12% of the high prevalence group needed to be effectively disqualified; even when all of the low prevalence group was disqualified, homicide did not decrease by 5%. An 18% increase in price similarly reduced firearm homicide by 5.37% (95% CI 4.43-6.31%). Firearm homicide declined monotonically as the proportion of disqualified individuals increased and/or price increased. A combined intervention that both increased price and effectively disqualified "high-risk" groups achieved approximately double the reduction in homicide as any one intervention alone. Increasing illegal firearm ownership by 20%, a hypothetical response to price increases, did not meaningfully change results.

CONCLUSION

A key takeaway of our study is that adopting high-risk versus population-based approaches should not be an "either-or" question. When individual risk is variable and diffuse in the population, "high-risk approaches" to firearm violence need to focus on relatively prevalent groups and be highly efficacious in disarming people at elevated risk to achieve meaningful reductions in firearm homicide, though countering issues of social justice and stigma should be carefully considered. Similar reductions can be achieved with population-based approaches, such as price increases, albeit with fewer such countering issues.

Promotion of behavioural change for health in a heterogeneous population

Public health policy often involves implementing cost-efficient, large-scale interventions. When mandating or forbidding a specific behaviour is not permissible, public health professionals may draw on behaviour change interventions to achieve socially beneficial policy objectives. Interventions can have two main effects: (i) a direct effect on people initially targeted by the intervention; and (ii) an indirect effect mediated by social influence and by the observation of other people's behaviour. However, people's attitudes and beliefs can differ markedly throughout the population, with the result that these two effects can interact to produce unexpected, unhelpful and counterintuitive consequences. Public health professionals need to understand this interaction better. This paper illustrates the key principles of this interaction by examining two important areas of public health policy: tobacco smoking and vaccination. The example of antismoking campaigns shows when and how public health professionals can amplify the effects of a behaviour change intervention by taking advantage of the indirect pathway. The example of vaccination campaigns illustrates how underlying incentive structures, particularly anticoordination incentives, can interfere with the indirect effect of an intervention and stall efforts to scale up its implementation. Recommendations are presented on how public health professionals can maximize the total effect of behaviour change interventions in heterogeneous populations based on these concepts and examples.

A Within-Individual Examination of the Predictors of Gun Carrying During Adolescence and Young Adulthood Among Young Men

Although prior studies have identified several risk factors for gun carrying, no prior longitudinal studies have examined a comprehensive set of explanatory factors together in within-individual change models or examined whether the predictors of gun carrying change across adolescence and early young adulthood. The present study fills these gaps by examining the predictive utility of several risk factors for gun carrying, and by examining whether any of the associations vary by age. The sample included 1216 young men who were arrested for the first time during adolescence (approximately 15 years old) and interviewed regularly for 5 years (until approximately 20 years old) after the first arrest. The outcome was youth-self-reported gun carrying and the risk factors included several variables consistent with various explanations for gun carrying (psychosocial maturity deficits; antisocial behavioral style; socialization; victimization). Research questions were addressed with fixed effects dynamic panel models (within-individual change models). Results showed that the most robust predictors of gun carrying were increased exposure to guns and gun-related violence and increased engagement in other antisocial and illegal behavior. The results emphasize the specific etiology of gun carrying and the potential social contagion effect of gun-related events. Overall, the study points to the need for prevention and intervention programs to specifically target the reduction of the real and perceived prevalence of gun-related events in young men's lives.

Non-fatal gun violence and community health behaviors: A neighborhood analysis in Philadelphia

Research shows that community violence is associated with an array of negative health outcomes, yet no study has examined the specific association between different types of gun violence and collective health behaviors in local neighborhoods. Using data from neighborhoods in the city of Philadelphia, this study examines the association between total, fatal, and non-fatal gun violence and measures of physical inactivity, obesity, sleep, and smoking. We find the rate of non-fatal shootings is associated with a composite measure of health behaviors, net of all neighborhood-level covariates and general community violence. Ancillary analyses show that non-fatal shootings are particularly associated with physical inactivity and obesity. Notably, fatal shootings are not associated with any behavioral health measure after accounting for nonlethal shootings. The results support improved data collection efforts to measure non-fatal shootings across the U.S. and greater attention to the collective health consequences of gun violence in local communities.

Simulating the Suicide Prevention Effects of Firearms Restrictions Based on Psychiatric Hospitalization and Treatment Records: Social Benefits and Unintended Adverse Consequences

Objectives. To estimate the number of lives saved from firearms suicide with expansions of gun restrictions based on mental health compared with the number who would be unnecessarily restricted. Methods. Agent-based models simulated effects on suicide mortality resulting from 5-year ownership disqualifications in New York City for individuals with any psychiatric hospitalization and, more broadly, anyone receiving psychiatric treatment. Results. Restrictions based on New York State Office of Mental Health-identified psychiatric hospitalizations reduced suicide among those hospitalized by 85.1% (95% credible interval = 36.5%, 100.0%). Disqualifications for anyone receiving psychiatric treatment reduced firearm suicide rates among those affected and in the population; however, 244 820 people were prohibited from firearm ownership who would not have died from firearm suicide even without the policy. Conclusions. In this simulation, denying firearm access to individuals in psychiatric treatment reduces firearm suicide among those groups but largely will not affect population rates. Broad and unfeasible disqualification criteria would needlessly restrict millions at low risk, with potential consequences for civil rights, increased stigma, and discouraged help seeking.

A Longitudinal Study of Gun Violence Attitudes: Role of Childhood Aggression and Exposure to Violence, and Early Adolescent Bullying Perpetration and Victimization

This prospective study examined the effects of early childhood physical aggression and violence exposure on bullying victimization/perpetration and attitudes toward guns and violence in early adolescence (EA) in a high-risk sample. Participants included 216 mother-child dyads from an ongoing longitudinal study using multi-method assessments (e.g., classroom observations, laboratory assessment, parent-, teacher-, and child self-reports). Results supported a developmental pathway from early adversity (i.e., prenatal substance use) to aggression at kindergarten age to bullying perpetration and gun violence attitudes (aggressive responses to shame) in EA. Higher peer victimization was also associated with aggressive responses to shame in EA. Results are discussed in light of the complexity of the motives for aggression and the need for prevention and early intervention.

Youth exposure to violence involving a gun: evidence for adverse childhood experience classification

Adverse childhood experiences (ACEs) have historically included child maltreatment, household dysfunction, and other critical issues known to impact children negatively. Although youth experiences with violence are broadly captured in some ACE measures, youth exposure to violence involving a gun has not been included specifically in the operationalizing, and therefore scientific study, of ACEs. There are numerous implications of this omission, including limiting access to ACE interventions that are currently available and resources for individuals who have been exposed to gun violence. Thus, and given the persistent prevalence of gun violence in the US, we conducted a systematic review of the literature over the past two decades on the assessment of and response to ACEs and gun violence. Eighty-one journal articles across four search engines met our inclusion criteria. Our findings provide evidence that youth gun violence exposure should be classified as an ACE. In addition to increasing access to resources for youth affected by gun violence, these findings may improve the likelihood of funding and research into gun violence, with direct implications for prevention and intervention efforts.

Assessing the impact of alcohol taxation on rates of violent victimization in a large urban area: an agent-based modeling approach

AIMS

To use simulation to estimate the impact of alcohol taxation on drinking, non-fatal violent victimization and homicide in New York City (NYC). We simulate the heterogeneous effects of alcohol price elasticities by income, level of consumption and beverage preferences, and examine whether taxation can reduce income inequalities in alcohol-related violence.

DESIGN

Agent-based modeling simulation.

SETTING

NYC, USA.

PARTICIPANTS

Adult population aged 18-64 years in the year 2000 in the 59 community districts of NYC. The population of 256 500 agents approximates a 5% sample of the NYC population.

MEASUREMENTS

Agents were parameterized through a series of rules that governed alcohol consumption and engagement in violence. Six taxation interventions were implemented based on extensive reviews and meta-analyses, increasing universal alcohol tax by 1, 5 and 10%, and beer tax by 1, 5 and 10%.

FINDINGS

Under no tax increase, approximately 12.2% [95% credible interval (prediction interval, PI) = 12.1-12.3%] were heavy drinkers. Taxation decreased the proportion of heavy drinkers; a 10% tax decreased heavy drinking to 9.6% (95% PI = 9.4-9.8). Beer taxes had the strongest effect on population consumption. Taxation influenced those in the lowest income groups more than the highest income groups. Alcohol-related homicide decreased from 3.22 per 100 000 (95% PI = 2.50-3.73) to 2.40 per 100 000 under a 10% universal tax (95% PI = 1.92-2.94). This translates into an anticipated benefit of ~1200 lives/year.

CONCLUSION

Reductions in alcohol consumption in a large urban environment such as New York City can be sustained with modest increases in universal taxation. Alcohol tax increases also have a modest effect on alcohol-related violent victimization. Taxation policies reduce income inequalities in alcohol-related violence.

Firearm Violence in Wilmington

Firearm related assault injuries disproportionately affect young men of color related to a variety of social & ecological vulnerabilities. Delaware, and particularly the city of Wilmington, has experienced a disproportionately high number of these injuries, and this article follows the public health approach in defining the scope of the problem, establishing what is known about the pathophysiology and transmission of injury, describing the effectiveness of newer prevention programs in both public safety and public health, and highlighting important constraints and considerations for program evaluation and research.

Global Mortality From Firearms, 1990-2016

Importance

Understanding global variation in firearm mortality rates could guide prevention policies and interventions.

Objective

To estimate mortality due to firearm injury deaths from 1990 to 2016 in 195 countries and territories.

Design, Setting, and Participants

This study used deidentified aggregated data including 13 812 location-years of vital registration data to generate estimates of levels and rates of death by age-sex-year-location. The proportion of suicides in which a firearm was the lethal means was combined with an estimate of per capita gun ownership in a revised proxy measure used to evaluate the relationship between availability or access to firearms and firearm injury deaths.

Exposures

Firearm ownership and access.

Main Outcomes and Measures

Cause-specific deaths by age, sex, location, and year.

Results

Worldwide, it was estimated that 251 000 (95% uncertainty interval [UI], 195 000-276 000) people died from firearm injuries in 2016, with 6 countries (Brazil, United States, Mexico, Colombia, Venezuela, and Guatemala) accounting for 50.5% (95% UI, 42.2%-54.8%) of those deaths. In 1990, there were an estimated 209 000 (95% UI, 172 000 to 235 000) deaths from firearm injuries. Globally, the majority of firearm injury deaths in 2016 were homicides (64.0% [95% UI, 54.2%-68.0%]; absolute value, 161 000 deaths [95% UI, 107 000-182 000]); additionally, 27% were firearm suicide deaths (67 500 [95% UI, 55 400-84 100]) and 9% were unintentional firearm deaths (23 000 [95% UI, 18 200-24 800]). From 1990 to 2016, there was no significant decrease in the estimated global age-standardized firearm homicide rate (-0.2% [95% UI, -0.8% to 0.2%]). Firearm suicide rates decreased globally at an annualized rate of 1.6% (95% UI, 1.1-2.0), but in 124 of 195 countries and territories included in this study, these levels were either constant or significant increases were estimated. There was an annualized decrease of 0.9% (95% UI, 0.5%-1.3%) in the global rate of age-standardized firearm deaths from 1990 to 2016. Aggregate firearm injury deaths in 2016 were highest among persons aged 20 to 24 years (for men, an estimated 34 700 deaths [95% UI, 24 900-39 700] and for women, an estimated 3580 deaths [95% UI, 2810-4210]). Estimates of the number of firearms by country were associated with higher rates of firearm suicide (P < .001; R2 = 0.21) and homicide (P < .001; R2 = 0.35).

Conclusions and Relevance

This study estimated between 195 000 and 276 000 firearm injury deaths globally in 2016, the majority of which were firearm homicides. Despite an overall decrease in rates of firearm injury death since 1990, there was variation among countries and across demographic subgroups.

The mitigating effects of maternal social support and paternal involvement on the intergenerational transmission of violence

Childhood maltreatment is a strong risk factor for subsequent violence, including violent behaviors in young adulthood and offspring maltreatment after becoming a parent. Little is known about the specific circumstances under which supportive relationships may help disrupt this cycle of violence throughout the life course. We conducted two complementary analyses to assess whether maternal social support in early childhood, and also paternal involvement in middle childhood, could prevent the intergenerational transmission of violence, using data from the Avon Longitudinal Study of Parents and Children (n=11,384). We found that higher levels of maternal social support in the postpartum period reduced the odds of offspring maltreatment at ages 0-8 years (OR=0.95, 95% CI 0.93-0.96). When classifying mothers according to their abuse history, this protective association of social support was observed among mothers with no history of childhood maltreatment and among those with only childhood maltreatment (and not postpartum intimate partner violence [IPV]), but not among mothers who reported IPV since the child's birth. We then extended our analysis of these offspring forward in time and found that paternal involvement at ages 9-10 years was associated with a reduced risk of offspring self-reported violent perpetration at ages 18-20 years (OR=0.85, 95% CI=0.77-0.94). This protective association was generally apparent among all subgroups of children, including those with a history of childhood maltreatment. Together these results highlight the protective influence of supportive relationships against the intergenerational transmission of violence, depending on abuse history, context, and timing, with important implications for the prevention of childhood maltreatment and mitigation of its negative effects.

Motivational Interviewing for Victims of Armed Community Violence: A Nonexperimental Pilot Feasibility Study

OBJECTIVE

The present study aimed to develop a novel, hospital-based motivational interviewing (MI) intervention for victims of armed community violence (MI-VoV) targeting patient-specific risk factors for future violence or violent victimization.

METHOD

This uncontrolled pilot feasibility study examined a sample of patients (n = 71) hospitalized due to violent injury at a Level 1 Trauma Center in [Location Redacted for Masked Review] between January 2013 and May 2014. Patients first participated in a brief assessment to identify risk factors for violence/violent injury. A single MI session then targeted risk behaviors identified for each patient. Proximal outcomes, including motivation for change and behaviors to reduce risk, were examined at 2 weeks and 6-12 weeks post-discharge. Distal outcomes, including fighting, weapon-carrying, and gun-carrying, and other violence risk factors were examined at 6-12 week follow-up.

RESULTS

Ninety-five patients were offered participation, 79 (83.2%) agreed to participate, and 73 (76.8%) completed the risk assessment. Of these, 71 had at least one violence/violent injury risk factor. Behaviors to reduce risk were significantly greater at two-week and 6-12 week follow-up (ps < .05). Fighting, weapon-carrying, gun-carrying were significantly reduced at 6-12 week follow-up (p < .05).

CONCLUSIONS

This intervention appears to be feasible to implement and acceptable to patients. A randomized controlled trial evaluating efficacy appears warranted.

Agent-Based Modeling in Public Health: Current Applications and Future Directions

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.

Reducing Urban Violence: A Contrast of Public Health and Criminal Justice Approaches

BACKGROUND

Cities are investing millions in Cure Violence, a public health approach to reduce urban violence by targeting at-risk youth and redirecting conflict to nonviolent responses. The impact of such a program compared with criminal justice responses is unknown because experiments directly comparing criminal justice and public health approaches to violence prevention are infeasible with observational data. We simulated experiments to test the influence of two interventions on violence: (1) Cure Violence and (2) directed police patrol in violence hot spots.

METHODS

We used an agent-based model to simulate a 5% sample of the New York City (NYC) adult population, with agents placed on a grid representing the land area of NYC, with neighborhood size and population density proportional to land area and population density in each community district. Agent behaviors were governed by parameters drawn from city data sources and published estimates.

RESULTS

Under no intervention, 3.87% (95% CI, 3.84, 3.90) of agents were victimized per year. Implementing the violence interrupter intervention for 10 years decreased victimization by 13% (to 3.35% [3.32, 3.39]). Implementing hot-spots policing and doubling the police force for 10 years reduced annual victimization by about 11% (to 3.46% [3.42, 3.49]). Increasing the police force by 40% combined with implementing the violence interrupter intervention for 10 years decreased violence by 19% (to 3.13% [3.09, 3.16]).

CONCLUSIONS

Combined investment in a public health, community-based approach to violence prevention and a criminal justice approach focused on deterrence can achieve more to reduce population-level rates of urban violence than either can in isolation. See video abstract at, http://links.lww.com/EDE/B298.

At the intersection of criminal justice involvement and sexual orientation: Dynamic networks and health among a population-based sample of young Black men who have sex with men

Mass incarceration of young Black men has a significant impact on their network composition and stability that, in turn, may have major implications for health and well-being. A sub-group of young Black men with criminal justice involvement (CJI) identify as gay, bisexual or are non-identified men who have sex with men (hereafter MSM). This paper focuses on the potential effects of CJI on the composition of Black MSM social and sexual networks, their stability over time, and concomitant health and social outcomes. We use data from the UConnect study, a population-based cohort of young Black MSM 16-29 years of age (n=618) selected using respondent-driven sampling in Chicago from 2013-2016. Both confidant and sexual network name generators and interpreters were administered at 9-month intervals over three waves of data collection. Ego and dyadic-level data were collected on behaviors prevalent among MSM and including factors associated with network CJI, network stability, and health outcomes. Generalized Structural Equation Models (GSEM) were utilized to determine the relationship between CJI network composition, network stability and behaviors prevalent among young Black MSM and their networks. In the UConnect cohort, 46% had at least once been detained, arrested or spent time in jail or prison. In addition, 20% of participants reported incident CJI over the study period. Respondents with a history of CJI were significantly more likely to have CJI homophily in their confidant and sexual networks. Multivariate analyses demonstrate that the association between one's history of CJI, housing instability and drug use is partially explained by one's network CJI. In addition, a higher prevalence of network CJI is associated with increased turnover in the confidant network, and this network instability is also related to important health and social outcomes. This analysis describes the networks of criminal justice involved men among a representative sample of young Black MSM and demonstrates the relationship between CJI network homophily, network stability and their impact on several key health and social outcomes relevant to this population.

Perceived popularity of adolescents who use weapons in violence and adolescents who only carry weapons

Prior research has found that persistently delinquent youth or more violent youth were less popular than their less delinquent peers (Young, 2013). However, recent research has also found that weapon carrying is associated with being more popular in adolescence (Dijkstra et al., 2010). The present paper examines the perceived popularity of adolescents who carry weapons in comparison to those who both carry and use weapons in acts of violence or threatened violence. Data consist of two waves from the National Longitudinal Study of Adolescent to Adult Health. Analyses use OLS regression with lagged predictors. This paper found no differences in number of friends between weapon carriers and weapon users. However, among both male and female gang members, those who did not use or carry weapons (abstainers) named significantly fewer friends than weapon users. Among females, weapon abstainers both named and were named by significantly more people than weapon users. These differences were not observed for males. Implications of these results and directions for future research are discussed.

The Role of Adolescent Friendship Group Integration and Cohesion in Weapon-Related Violent Crime as a Young Adult

Weapon-related violent crime is a serious, complex, and multifaceted public health problem. The present study uses data from Waves I and III of Add Health (n = 10,482, 54% female) to examine how friendship group integration and cohesion in adolescence (ages 12-19) is associated with weapon-related criminal activity as a young adult (ages 18-26). Results indicate that greater cohesion in friendship groups is associated with significantly lower weapon-related criminal activity in young adulthood. In addition, for adolescent girls, a greater number of close friendship ties-an indicator of friendship group integration-is associated with less weapon-related criminal activity in young adulthood. These findings suggest that school-based initiatives to facilitate inclusive and cohesive adolescent peer communities may be an effective strategy to curb weapon-related criminal activity in young adulthood.

The Contagious Spread of Violence Among US Adolescents Through Social Networks

OBJECTIVES

To test the hypothesis that violence among US adolescents spreads like a contagious disease through social networks.

METHODS

Participants were a nationally representative sample of 90 118 US students aged 12 to 18 years who were involved in the National Longitudinal Study of Adolescent Health. Violence was assessed by having participants report the number of times in the preceding 12 months they had been involved in a serious physical fight, had hurt someone badly, and had pulled a weapon on someone.

RESULTS

Participants were 48% more likely to have been involved in a serious fight, 183% more likely to have hurt someone badly, and 140% more likely to have pulled a weapon on someone if a friend had engaged in the same behavior. The influence spread up to 4 degrees of separation (i.e., friend of friend of friend of friend) for serious fights, 2 degrees for hurting someone badly, and 3 degrees for pulling a weapon on someone.

CONCLUSIONS

Adolescents were more likely to engage in violent behavior if their friends did the same, and contagion of violence extended beyond immediate friends to friends of friends.

Epidemiologic Evidence to Guide the Understanding and Prevention of Gun Violence

Gunfire from assaults, suicides, and unintentional shootings exacts an enormous burden on public health globally. The epidemiologic reviews in this special issue enhance our understanding of various forms of gun violence, inform interventions, and help chart directions for future research. The available science, however, is limited to answer many important questions necessary for mounting successful efforts to reduce gun violence. Certain data are lacking, and there are numerous analytical challenges to deriving unbiased estimates of policy impacts. Significant investments in research over the long term are warranted to answer questions central to successful prevention of gun violence.