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This article discusses the opportunities and challenges of developing research designs to evaluate the impact of community-level prevention efforts. To illustrate examples of evaluation designs, we describe six projects funded by the Centers for Disease Control and Prevention to evaluate multifaceted approaches to reduce youth violence in high-risk communities. Each of these projects was designed to evaluate the community-level impact of multiple intervention strategies to address individual and contextual factors that place youth at risk for violent behavior. Communities differed across projects in their setting, size, and how their boundaries were defined. Each project is using multiple approaches to compare outcomes in one or more intervention communities to those in comparison communities. Five of the projects are using comparative interrupted time-series designs to compare outcomes in an intervention community to matched comparison communities. A sixth project is using a multiple baseline design in which the order and timing of intervention activities is randomized across three communities. All six projects are also using regression point displacement designs to compare outcomes within intervention communities to those within broader sets of similar communities. Projects are using a variety of approaches to assess outcomes including archival records, surveys, and direct observations. We discuss the strengths and weaknesses of the designs of these projects and illustrate the challenges of designing high-quality evaluations of comprehensive prevention approaches implemented at the community level.

Background: Frameworks for studying the ecology of human behavior suggest that multiple levels of the environment influence behavior and that these levels interact. Applied to studies of weapons aggression, this suggests proximal risk factor (e.g., substance use) effects may differ across neighborhoods., Objectives: To estimate how the association between weapons aggression and substance use varies as a function of several community-level variables., Methods: Individual-level measures (demographics, behavioral measures) were obtained from a survey of youth aged 14-24 years old seeking care at a Level-1 ED in Flint, Michigan. Community-level variables were obtained from public sources. Logistic generalized additive models were used to test whether community-level variables (crime rates, alcohol outlets, demographics) modify the link between individual-level substance use variables and the primary outcome measure: self-reported past 6-month weapon (firearm/knife) related aggression., Results: The effect of marijuana misuse on weapons aggression varied significantly as a function of five community-level variables: racial composition, vacant housing rates, female headed household rates, density of package alcohol outlets, and nearby drug crime rates. The effect of high-risk alcohol use did not depend on any of the eight community variables tested., Conclusions: The relationship between marijuana misuse and weapons aggression differed across neighborhoods with generally less association in more disadvantaged neighborhoods, while high-risk alcohol use showed a consistently high association with weapons aggression that did not vary across neighborhoods. The results aid in understanding the contributions of alcohol and marijuana use to the etiology of weapon-related aggression among urban youth, but further study in the general population is required.