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Most homicides in the United States are committed using a handgun, but little research examines gun carrying over critical stages of the life course and changing contexts of violence. Notably, although most of the handgun homicides are committed by adults, most research on concealed gun carrying focuses on adolescents in single cohort studies. Using more than 25 years of longitudinal multicohort data from Chicago, 1994-2021, we show that pathways of concealed gun carrying are distinct between adolescence and adulthood. Adolescent carrying is often age-limited and responsive to direct exposure to gun violence (witnessing and victimization), while adult carrying is a persistent behavior that is less tied to direct exposure. The onset of concealed carry is also a strong predictor of later gun use (shooting or brandishing), and we find distinct patterns of gun use between individuals who first carry in adolescence versus adulthood. We discuss the implications of these dual pathways for research and policies on firearm use.

Importance: The past quarter-century has seen both sharp declines and increases in firearm violence in the United States. Yet, little is known about the age of first exposure to firearm violence and how it may differ by race, sex, and cohort., Objective: To examine race, sex, and cohort differences in exposure to firearm violence in a representative longitudinal study of children who grew up in periods with varying rates of firearm violence in the United States and to examine spatial proximity to firearm violence in adulthood., Design, Setting, and Participants: This population-based representative cohort study included multiple cohorts of children followed-up from 1995 through 2021 in the Project on Human Development in Chicago Neighborhoods (PHDCN). Participants included Black, Hispanic, and White respondents from 4 age cohorts of Chicago, Illinois, residents, with modal birth years of 1981, 1984, 1987, and 1996. Data analyses were conducted from May 2022 to March 2023., Main Outcomes and Measures: Firearm violence exposure, including age when first shot, age when first saw someone shot, and past-year frequency of fatal and nonfatal shootings within 250 m of residence., Results: There were 2418 participants in wave 1 (in the mid-1990s), and they were evenly split by sex, with 1209 males (50.00%) and 1209 females (50.00%). There were 890 Black respondents, 1146 Hispanic respondents, and 382 White respondents. Male respondents were much more likely than female respondents to have been shot (adjusted hazard ratio [aHR], 4.23; 95% CI, 2.28-7.84), but only moderately more likely to have seen someone shot (aHR, 1.48; 95% CI, 1.27-1.72). Compared with White individuals, Black individuals experienced higher rates of all 3 forms of exposure (been shot: aHR, 3.05; 95% CI, 1.22-7.60; seen someone shot: aHR, 4.69; 95% CI, 3.41-6.46; nearby shootings: adjusted incidence rate ratio [aIRR], 12.40; 95% CI, 6.88-22.35), and Hispanic respondents experienced higher rates of 2 forms of violence exposure (seen someone shot: aHR, 2.59; 95% CI, 1.85-3.62; nearby shootings: aIRR, 3.77; 95% CI, 2.08-6.84). Respondents born in the mid-1990s who grew up amidst large declines in homicide but reached adulthood during city and national spikes in firearm violence in 2016 were less likely to have seen someone shot than those born in the early 1980s who grew up during the peak of homicide in the early 1990s (aHR, 0.49; 95% CI, 0.35-0.69). However, the likelihood of having been shot did not significantly differ between these cohorts (aHR, 0.81; 95% CI, 0.40-1.63)., Conclusions and Relevance: In this longitudinal multicohort study of exposure to firearm violence, there were stark differences by race and sex, yet the extent of exposure to violence was not simply the product of these characteristics. These findings on cohort differences suggest changing societal conditions were key factors associated with whether and at what life stage individuals from all race and sex groups were exposed to firearm violence.

Background: Lead exposure remains highly prevalent worldwide despite decades of research highlighting its link to numerous adverse health outcomes. In addition to well-documented effects on cognition, there is growing evidence of an association with antisocial behavior, including aggression, conduct problems, and crime. An updated systematic review on this topic, incorporating study evaluation and a developmental perspective on the outcome, can advance the state of the science on lead and inform global policy interventions to reduce exposure., Objectives: We aim to evaluate the link between lead exposure and antisocial behavior. This association will be investigated via a systematic review of human epidemiological and experimental nonhuman mammalian studies., Methods: The systematic review protocol presented in this publication is informed by recommendations for the conduct of systematic reviews in toxicology and environmental health research (COSTER) and follows the study evaluation approach put forth by the U.S. EPA Integrated Risk Information System (IRIS) program., Data Sources: We will search the following electronic databases for relevant literature: PubMed, BIOSIS and Web of Science. Search results will be stored in EPA's Health and Environmental Research Online (HERO) database., Study Eligibility and Criteria: Eligible human epidemiological studies will include those evaluating any population exposed to lead at any lifestage via ingestion or inhalation exposure and considering an outcome of antisocial behavior based on any of the following criteria: psychiatric diagnoses (e.g., oppositional defiant disorder (ODD), conduct disorder (CD), disruptive behavior disorders (DBD)); violation of social norms (e.g., delinquency, criminality); and aggression. Eligible experimental animal studies will include those evaluating nonhuman mammalian studies exposed to lead via ingestion, inhalation, or injection exposure during any lifestage. The following outcomes will be considered relevant: aggression; antisocial behavior; and altered fear, anxiety, and stress response., Study Appraisal and Synthesis Methods: Screening will be conducted with assistance from an artificial intelligence application. Two independent reviewers for each data stream (human, animal) will screen studies with highest predicted relevance against pre-specified inclusion criteria at the title/abstract and full-text level. Study evaluation will be conducted using methods adapted from the U.S. EPA IRIS program. After data extraction, we will conduct a narrative review and quantitative meta-analysis on the human epidemiological studies as well as a narrative review of the experimental animal studies. We will evaluate the strength of each evidence stream separately and then will develop a summary evidence integration statement based on inference across evidence streams., Competing Interests: Declaration of Competing Interest All authors except H.H. declare they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Howard Hu reports a relationship with lead exposure litigation (various) that includes: consulting or advisory and paid expert testimony., (Published by Elsevier Ltd.)

Collective efficacy is a prominent explanation for neighborhood crime concentrations. Just as crime is concentrated in particular neighborhoods, within-neighborhoods crime is concentrated in particular criminogenic locations. Research suggests criminogenic locations are determined by features of the built environment. This study links collective efficacy with situational opportunity to propose that collective efficacy facilitates the removal of criminogenic features of the built environment. I test this by examining associations 1) between past collective efficacy and present criminogenic features of the built environment, as well as 2) between those built environment features and crime, net of present collective efficacy. These are modeled using piecewise structural equations with generalized linear mixed-effect regressions on data from 1,641 blocks in 343 Chicago neighborhoods. Four types of police-reported crime are modeled using eight block-level built environment features in the 2003 Chicago Community Area Health Study (CCAHS; N = 3,074) and neighborhood collective efficacy from the CCAHS and the 1995 Project in Human Development in Chicago Neighborhoods (PHDCN) Community Survey (N = 7,672). Findings suggest neighborhoods with high collective efficacy maintain low rates of crime in part by limiting criminogenic built environment features, in particular, abandoned buildings. This crime control pathway is important because changes to the built environment are long lasting and reduce the need for future interventions against crime., (© 2022 The Authors. Criminology published by Wiley Periodicals LLC on behalf of American Society of Criminology.)

An important criminological controversy concerns the proper causal relationships between disorder, informal social control, and crime. The broken windows thesis posits that neighborhood disorder increases crime directly and indirectly by undermining neighborhood informal social control. Theories of collective efficacy argue that the association between neighborhood disorder and crime is spurious because of the confounding variable informal social control. We review the recent empirical research on this question, which uses disparate methods, including field experiments and different models for observational data. To evaluate the causal claims made in these studies, we use a potential outcomes framework of causality. We conclude that, although there is some evidence for both broken windows and informal control theories, there is little consensus in the present research literature. Furthermore, at present, most studies do not establish causality in a strong way.